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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * NILFS segment constructor.
  *
  * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
  *
  * Written by Ryusuke Konishi.
  *
  */
 
 #include <linux/pagemap.h>
 #include <linux/buffer_head.h>
 #include <linux/writeback.h>
 #include <linux/bitops.h>
 #include <linux/bio.h>
 #include <linux/completion.h>
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
 #include <linux/freezer.h>
 #include <linux/kthread.h>
 #include <linux/crc32.h>
 #include <linux/pagevec.h>
 #include <linux/slab.h>
 #include <linux/sched/signal.h>
 
 #include "nilfs.h"
 #include "btnode.h"
 #include "page.h"
 #include "segment.h"
 #include "sufile.h"
 #include "cpfile.h"
 #include "ifile.h"
 #include "segbuf.h"
 
 
 /*
  * Segment constructor
  */
 #define SC_N_INODEVEC   16   /* Size of locally allocated inode vector */
 
 #define SC_MAX_SEGDELTA 64   /*
                   * Upper limit of the number of segments
                   * appended in collection retry loop
                   */
 
 /* Construction mode */
 enum {
     SC_LSEG_SR = 1, /* Make a logical segment having a super root */
     SC_LSEG_DSYNC,  /*
              * Flush data blocks of a given file and make
              * a logical segment without a super root.
              */
     SC_FLUSH_FILE,  /*
              * Flush data files, leads to segment writes without
              * creating a checkpoint.
              */
     SC_FLUSH_DAT,   /*
              * Flush DAT file.  This also creates segments
              * without a checkpoint.
              */
 };
 
 /* Stage numbers of dirty block collection */
 enum {
     NILFS_ST_INIT = 0,
     NILFS_ST_GC,        /* Collecting dirty blocks for GC */
     NILFS_ST_FILE,
     NILFS_ST_IFILE,
     NILFS_ST_CPFILE,
     NILFS_ST_SUFILE,
     NILFS_ST_DAT,
     NILFS_ST_SR,        /* Super root */
     NILFS_ST_DSYNC,     /* Data sync blocks */
     NILFS_ST_DONE,
 };
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/nilfs2.h>
 
 /*
  * nilfs_sc_cstage_inc(), nilfs_sc_cstage_set(), nilfs_sc_cstage_get() are
  * wrapper functions of stage count (nilfs_sc_info->sc_stage.scnt). Users of
  * the variable must use them because transition of stage count must involve
  * trace events (trace_nilfs2_collection_stage_transition).
  *
  * nilfs_sc_cstage_get() isn't required for the above purpose because it doesn't
  * produce tracepoint events. It is provided just for making the intention
  * clear.
  */
 static inline void nilfs_sc_cstage_inc(struct nilfs_sc_info *sci)
 {
     sci->sc_stage.scnt++;
     trace_nilfs2_collection_stage_transition(sci);
 }
 
 static inline void nilfs_sc_cstage_set(struct nilfs_sc_info *sci, int next_scnt)
 {
     sci->sc_stage.scnt = next_scnt;
     trace_nilfs2_collection_stage_transition(sci);
 }
 
 static inline int nilfs_sc_cstage_get(struct nilfs_sc_info *sci)
 {
     return sci->sc_stage.scnt;
 }
 
 /* State flags of collection */
 #define NILFS_CF_NODE       0x0001  /* Collecting node blocks */
 #define NILFS_CF_IFILE_STARTED  0x0002  /* IFILE stage has started */
 #define NILFS_CF_SUFREED    0x0004  /* segment usages has been freed */
 #define NILFS_CF_HISTORY_MASK   (NILFS_CF_IFILE_STARTED | NILFS_CF_SUFREED)
 
 /* Operations depending on the construction mode and file type */
 struct nilfs_sc_operations {
     int (*collect_data)(struct nilfs_sc_info *, struct buffer_head *,
                 struct inode *);
     int (*collect_node)(struct nilfs_sc_info *, struct buffer_head *,
                 struct inode *);
     int (*collect_bmap)(struct nilfs_sc_info *, struct buffer_head *,
                 struct inode *);
     void (*write_data_binfo)(struct nilfs_sc_info *,
                  struct nilfs_segsum_pointer *,
                  union nilfs_binfo *);
     void (*write_node_binfo)(struct nilfs_sc_info *,
                  struct nilfs_segsum_pointer *,
                  union nilfs_binfo *);
 };
 
 /*
  * Other definitions
  */
 static void nilfs_segctor_start_timer(struct nilfs_sc_info *);
 static void nilfs_segctor_do_flush(struct nilfs_sc_info *, int);
 static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *);
 static void nilfs_dispose_list(struct the_nilfs *, struct list_head *, int);
 
 #define nilfs_cnt32_ge(a, b)   \
     (typecheck(__u32, a) && typecheck(__u32, b) && \
      ((__s32)(a) - (__s32)(b) >= 0))
 
 static int nilfs_prepare_segment_lock(struct super_block *sb,
                       struct nilfs_transaction_info *ti)
 {
     struct nilfs_transaction_info *cur_ti = current->journal_info;
     void *save = NULL;
 
     if (cur_ti) {
         if (cur_ti->ti_magic == NILFS_TI_MAGIC)
             return ++cur_ti->ti_count;
 
         /*
          * If journal_info field is occupied by other FS,
          * it is saved and will be restored on
          * nilfs_transaction_commit().
          */
         nilfs_warn(sb, "journal info from a different FS");
         save = current->journal_info;
     }
     if (!ti) {
         ti = kmem_cache_alloc(nilfs_transaction_cachep, GFP_NOFS);
         if (!ti)
             return -ENOMEM;
         ti->ti_flags = NILFS_TI_DYNAMIC_ALLOC;
     } else {
         ti->ti_flags = 0;
     }
     ti->ti_count = 0;
     ti->ti_save = save;
     ti->ti_magic = NILFS_TI_MAGIC;
     current->journal_info = ti;
     return 0;
 }
 
 /**
  * nilfs_transaction_begin - start indivisible file operations.
  * @sb: super block
  * @ti: nilfs_transaction_info
  * @vacancy_check: flags for vacancy rate checks
  *
  * nilfs_transaction_begin() acquires a reader/writer semaphore, called
  * the segment semaphore, to make a segment construction and write tasks
  * exclusive.  The function is used with nilfs_transaction_commit() in pairs.
  * The region enclosed by these two functions can be nested.  To avoid a
  * deadlock, the semaphore is only acquired or released in the outermost call.
  *
  * This function allocates a nilfs_transaction_info struct to keep context
  * information on it.  It is initialized and hooked onto the current task in
  * the outermost call.  If a pre-allocated struct is given to @ti, it is used
  * instead; otherwise a new struct is assigned from a slab.
  *
  * When @vacancy_check flag is set, this function will check the amount of
  * free space, and will wait for the GC to reclaim disk space if low capacity.
  *
  * Return Value: On success, 0 is returned. On error, one of the following
  * negative error code is returned.
  *
  * %-ENOMEM - Insufficient memory available.
  *
  * %-ENOSPC - No space left on device
  */
 int nilfs_transaction_begin(struct super_block *sb,
                 struct nilfs_transaction_info *ti,
                 int vacancy_check)
 {
     struct the_nilfs *nilfs;
     int ret = nilfs_prepare_segment_lock(sb, ti);
     struct nilfs_transaction_info *trace_ti;
 
     if (unlikely(ret < 0))
         return ret;
     if (ret > 0) {
         trace_ti = current->journal_info;
 
         trace_nilfs2_transaction_transition(sb, trace_ti,
                     trace_ti->ti_count, trace_ti->ti_flags,
                     TRACE_NILFS2_TRANSACTION_BEGIN);
         return 0;
     }
 
     sb_start_intwrite(sb);
 
     nilfs = sb->s_fs_info;
     down_read(&nilfs->ns_segctor_sem);
     if (vacancy_check && nilfs_near_disk_full(nilfs)) {
         up_read(&nilfs->ns_segctor_sem);
         ret = -ENOSPC;
         goto failed;
     }
 
     trace_ti = current->journal_info;
     trace_nilfs2_transaction_transition(sb, trace_ti, trace_ti->ti_count,
                         trace_ti->ti_flags,
                         TRACE_NILFS2_TRANSACTION_BEGIN);
     return 0;
 
  failed:
     ti = current->journal_info;
     current->journal_info = ti->ti_save;
     if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
         kmem_cache_free(nilfs_transaction_cachep, ti);
     sb_end_intwrite(sb);
     return ret;
 }
 
 /**
  * nilfs_transaction_commit - commit indivisible file operations.
  * @sb: super block
  *
  * nilfs_transaction_commit() releases the read semaphore which is
  * acquired by nilfs_transaction_begin(). This is only performed
  * in outermost call of this function.  If a commit flag is set,
  * nilfs_transaction_commit() sets a timer to start the segment
  * constructor.  If a sync flag is set, it starts construction
  * directly.
  */
 int nilfs_transaction_commit(struct super_block *sb)
 {
     struct nilfs_transaction_info *ti = current->journal_info;
     struct the_nilfs *nilfs = sb->s_fs_info;
     int err = 0;
 
     BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
     ti->ti_flags |= NILFS_TI_COMMIT;
     if (ti->ti_count > 0) {
         ti->ti_count--;
         trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
                 ti->ti_flags, TRACE_NILFS2_TRANSACTION_COMMIT);
         return 0;
     }
     if (nilfs->ns_writer) {
         struct nilfs_sc_info *sci = nilfs->ns_writer;
 
         if (ti->ti_flags & NILFS_TI_COMMIT)
             nilfs_segctor_start_timer(sci);
         if (atomic_read(&nilfs->ns_ndirtyblks) > sci->sc_watermark)
             nilfs_segctor_do_flush(sci, 0);
     }
     up_read(&nilfs->ns_segctor_sem);
     trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
                 ti->ti_flags, TRACE_NILFS2_TRANSACTION_COMMIT);
 
     current->journal_info = ti->ti_save;
 
     if (ti->ti_flags & NILFS_TI_SYNC)
         err = nilfs_construct_segment(sb);
     if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
         kmem_cache_free(nilfs_transaction_cachep, ti);
     sb_end_intwrite(sb);
     return err;
 }
 
 void nilfs_transaction_abort(struct super_block *sb)
 {
     struct nilfs_transaction_info *ti = current->journal_info;
     struct the_nilfs *nilfs = sb->s_fs_info;
 
     BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
     if (ti->ti_count > 0) {
         ti->ti_count--;
         trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
                 ti->ti_flags, TRACE_NILFS2_TRANSACTION_ABORT);
         return;
     }
     up_read(&nilfs->ns_segctor_sem);
 
     trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
             ti->ti_flags, TRACE_NILFS2_TRANSACTION_ABORT);
 
     current->journal_info = ti->ti_save;
     if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
         kmem_cache_free(nilfs_transaction_cachep, ti);
     sb_end_intwrite(sb);
 }
 
 void nilfs_relax_pressure_in_lock(struct super_block *sb)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     struct nilfs_sc_info *sci = nilfs->ns_writer;
 
     if (!sci || !sci->sc_flush_request)
         return;
 
     set_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
     up_read(&nilfs->ns_segctor_sem);
 
     down_write(&nilfs->ns_segctor_sem);
     if (sci->sc_flush_request &&
         test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags)) {
         struct nilfs_transaction_info *ti = current->journal_info;
 
         ti->ti_flags |= NILFS_TI_WRITER;
         nilfs_segctor_do_immediate_flush(sci);
         ti->ti_flags &= ~NILFS_TI_WRITER;
     }
     downgrade_write(&nilfs->ns_segctor_sem);
 }
 
 static void nilfs_transaction_lock(struct super_block *sb,
                    struct nilfs_transaction_info *ti,
                    int gcflag)
 {
     struct nilfs_transaction_info *cur_ti = current->journal_info;
     struct the_nilfs *nilfs = sb->s_fs_info;
     struct nilfs_sc_info *sci = nilfs->ns_writer;
 
     WARN_ON(cur_ti);
     ti->ti_flags = NILFS_TI_WRITER;
     ti->ti_count = 0;
     ti->ti_save = cur_ti;
     ti->ti_magic = NILFS_TI_MAGIC;
     current->journal_info = ti;
 
     for (;;) {
         trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
                 ti->ti_flags, TRACE_NILFS2_TRANSACTION_TRYLOCK);
 
         down_write(&nilfs->ns_segctor_sem);
         if (!test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags))
             break;
 
         nilfs_segctor_do_immediate_flush(sci);
 
         up_write(&nilfs->ns_segctor_sem);
         cond_resched();
     }
     if (gcflag)
         ti->ti_flags |= NILFS_TI_GC;
 
     trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
                 ti->ti_flags, TRACE_NILFS2_TRANSACTION_LOCK);
 }
 
 static void nilfs_transaction_unlock(struct super_block *sb)
 {
     struct nilfs_transaction_info *ti = current->journal_info;
     struct the_nilfs *nilfs = sb->s_fs_info;
 
     BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
     BUG_ON(ti->ti_count > 0);
 
     up_write(&nilfs->ns_segctor_sem);
     current->journal_info = ti->ti_save;
 
     trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
                 ti->ti_flags, TRACE_NILFS2_TRANSACTION_UNLOCK);
 }
 
 static void *nilfs_segctor_map_segsum_entry(struct nilfs_sc_info *sci,
                         struct nilfs_segsum_pointer *ssp,
                         unsigned int bytes)
 {
     struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
     unsigned int blocksize = sci->sc_super->s_blocksize;
     void *p;
 
     if (unlikely(ssp->offset + bytes > blocksize)) {
         ssp->offset = 0;
         BUG_ON(NILFS_SEGBUF_BH_IS_LAST(ssp->bh,
                            &segbuf->sb_segsum_buffers));
         ssp->bh = NILFS_SEGBUF_NEXT_BH(ssp->bh);
     }
     p = ssp->bh->b_data + ssp->offset;
     ssp->offset += bytes;
     return p;
 }
 
 /**
  * nilfs_segctor_reset_segment_buffer - reset the current segment buffer
  * @sci: nilfs_sc_info
  */
 static int nilfs_segctor_reset_segment_buffer(struct nilfs_sc_info *sci)
 {
     struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
     struct buffer_head *sumbh;
     unsigned int sumbytes;
     unsigned int flags = 0;
     int err;
 
     if (nilfs_doing_gc())
         flags = NILFS_SS_GC;
     err = nilfs_segbuf_reset(segbuf, flags, sci->sc_seg_ctime, sci->sc_cno);
     if (unlikely(err))
         return err;
 
     sumbh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
     sumbytes = segbuf->sb_sum.sumbytes;
     sci->sc_finfo_ptr.bh = sumbh;  sci->sc_finfo_ptr.offset = sumbytes;
     sci->sc_binfo_ptr.bh = sumbh;  sci->sc_binfo_ptr.offset = sumbytes;
     sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
     return 0;
 }
 
 static int nilfs_segctor_feed_segment(struct nilfs_sc_info *sci)
 {
     sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
     if (NILFS_SEGBUF_IS_LAST(sci->sc_curseg, &sci->sc_segbufs))
         return -E2BIG; /*
                 * The current segment is filled up
                 * (internal code)
                 */
     sci->sc_curseg = NILFS_NEXT_SEGBUF(sci->sc_curseg);
     return nilfs_segctor_reset_segment_buffer(sci);
 }
 
 static int nilfs_segctor_add_super_root(struct nilfs_sc_info *sci)
 {
     struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
     int err;
 
     if (segbuf->sb_sum.nblocks >= segbuf->sb_rest_blocks) {
         err = nilfs_segctor_feed_segment(sci);
         if (err)
             return err;
         segbuf = sci->sc_curseg;
     }
     err = nilfs_segbuf_extend_payload(segbuf, &segbuf->sb_super_root);
     if (likely(!err))
         segbuf->sb_sum.flags |= NILFS_SS_SR;
     return err;
 }
 
 /*
  * Functions for making segment summary and payloads
  */
 static int nilfs_segctor_segsum_block_required(
     struct nilfs_sc_info *sci, const struct nilfs_segsum_pointer *ssp,
     unsigned int binfo_size)
 {
     unsigned int blocksize = sci->sc_super->s_blocksize;
     /* Size of finfo and binfo is enough small against blocksize */
 
     return ssp->offset + binfo_size +
         (!sci->sc_blk_cnt ? sizeof(struct nilfs_finfo) : 0) >
         blocksize;
 }
 
 static void nilfs_segctor_begin_finfo(struct nilfs_sc_info *sci,
                       struct inode *inode)
 {
     sci->sc_curseg->sb_sum.nfinfo++;
     sci->sc_binfo_ptr = sci->sc_finfo_ptr;
     nilfs_segctor_map_segsum_entry(
         sci, &sci->sc_binfo_ptr, sizeof(struct nilfs_finfo));
 
     if (NILFS_I(inode)->i_root &&
         !test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
         set_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
     /* skip finfo */
 }
 
 static void nilfs_segctor_end_finfo(struct nilfs_sc_info *sci,
                     struct inode *inode)
 {
     struct nilfs_finfo *finfo;
     struct nilfs_inode_info *ii;
     struct nilfs_segment_buffer *segbuf;
     __u64 cno;
 
     if (sci->sc_blk_cnt == 0)
         return;
 
     ii = NILFS_I(inode);
 
     if (test_bit(NILFS_I_GCINODE, &ii->i_state))
         cno = ii->i_cno;
     else if (NILFS_ROOT_METADATA_FILE(inode->i_ino))
         cno = 0;
     else
         cno = sci->sc_cno;
 
     finfo = nilfs_segctor_map_segsum_entry(sci, &sci->sc_finfo_ptr,
                          sizeof(*finfo));
     finfo->fi_ino = cpu_to_le64(inode->i_ino);
     finfo->fi_nblocks = cpu_to_le32(sci->sc_blk_cnt);
     finfo->fi_ndatablk = cpu_to_le32(sci->sc_datablk_cnt);
     finfo->fi_cno = cpu_to_le64(cno);
 
     segbuf = sci->sc_curseg;
     segbuf->sb_sum.sumbytes = sci->sc_binfo_ptr.offset +
         sci->sc_super->s_blocksize * (segbuf->sb_sum.nsumblk - 1);
     sci->sc_finfo_ptr = sci->sc_binfo_ptr;
     sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
 }
 
 static int nilfs_segctor_add_file_block(struct nilfs_sc_info *sci,
                     struct buffer_head *bh,
                     struct inode *inode,
                     unsigned int binfo_size)
 {
     struct nilfs_segment_buffer *segbuf;
     int required, err = 0;
 
  retry:
     segbuf = sci->sc_curseg;
     required = nilfs_segctor_segsum_block_required(
         sci, &sci->sc_binfo_ptr, binfo_size);
     if (segbuf->sb_sum.nblocks + required + 1 > segbuf->sb_rest_blocks) {
         nilfs_segctor_end_finfo(sci, inode);
         err = nilfs_segctor_feed_segment(sci);
         if (err)
             return err;
         goto retry;
     }
     if (unlikely(required)) {
         err = nilfs_segbuf_extend_segsum(segbuf);
         if (unlikely(err))
             goto failed;
     }
     if (sci->sc_blk_cnt == 0)
         nilfs_segctor_begin_finfo(sci, inode);
 
     nilfs_segctor_map_segsum_entry(sci, &sci->sc_binfo_ptr, binfo_size);
     /* Substitution to vblocknr is delayed until update_blocknr() */
     nilfs_segbuf_add_file_buffer(segbuf, bh);
     sci->sc_blk_cnt++;
  failed:
     return err;
 }
 
 /*
  * Callback functions that enumerate, mark, and collect dirty blocks
  */
 static int nilfs_collect_file_data(struct nilfs_sc_info *sci,
                    struct buffer_head *bh, struct inode *inode)
 {
     int err;
 
     err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
     if (err < 0)
         return err;
 
     err = nilfs_segctor_add_file_block(sci, bh, inode,
                        sizeof(struct nilfs_binfo_v));
     if (!err)
         sci->sc_datablk_cnt++;
     return err;
 }
 
 static int nilfs_collect_file_node(struct nilfs_sc_info *sci,
                    struct buffer_head *bh,
                    struct inode *inode)
 {
     return nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
 }
 
 static int nilfs_collect_file_bmap(struct nilfs_sc_info *sci,
                    struct buffer_head *bh,
                    struct inode *inode)
 {
     WARN_ON(!buffer_dirty(bh));
     return nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
 }
 
 static void nilfs_write_file_data_binfo(struct nilfs_sc_info *sci,
                     struct nilfs_segsum_pointer *ssp,
                     union nilfs_binfo *binfo)
 {
     struct nilfs_binfo_v *binfo_v = nilfs_segctor_map_segsum_entry(
         sci, ssp, sizeof(*binfo_v));
     *binfo_v = binfo->bi_v;
 }
 
 static void nilfs_write_file_node_binfo(struct nilfs_sc_info *sci,
                     struct nilfs_segsum_pointer *ssp,
                     union nilfs_binfo *binfo)
 {
     __le64 *vblocknr = nilfs_segctor_map_segsum_entry(
         sci, ssp, sizeof(*vblocknr));
     *vblocknr = binfo->bi_v.bi_vblocknr;
 }
 
 static const struct nilfs_sc_operations nilfs_sc_file_ops = {
     .collect_data = nilfs_collect_file_data,
     .collect_node = nilfs_collect_file_node,
     .collect_bmap = nilfs_collect_file_bmap,
     .write_data_binfo = nilfs_write_file_data_binfo,
     .write_node_binfo = nilfs_write_file_node_binfo,
 };
 
 static int nilfs_collect_dat_data(struct nilfs_sc_info *sci,
                   struct buffer_head *bh, struct inode *inode)
 {
     int err;
 
     err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
     if (err < 0)
         return err;
 
     err = nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
     if (!err)
         sci->sc_datablk_cnt++;
     return err;
 }
 
 static int nilfs_collect_dat_bmap(struct nilfs_sc_info *sci,
                   struct buffer_head *bh, struct inode *inode)
 {
     WARN_ON(!buffer_dirty(bh));
     return nilfs_segctor_add_file_block(sci, bh, inode,
                         sizeof(struct nilfs_binfo_dat));
 }
 
 static void nilfs_write_dat_data_binfo(struct nilfs_sc_info *sci,
                        struct nilfs_segsum_pointer *ssp,
                        union nilfs_binfo *binfo)
 {
     __le64 *blkoff = nilfs_segctor_map_segsum_entry(sci, ssp,
                               sizeof(*blkoff));
     *blkoff = binfo->bi_dat.bi_blkoff;
 }
 
 static void nilfs_write_dat_node_binfo(struct nilfs_sc_info *sci,
                        struct nilfs_segsum_pointer *ssp,
                        union nilfs_binfo *binfo)
 {
     struct nilfs_binfo_dat *binfo_dat =
         nilfs_segctor_map_segsum_entry(sci, ssp, sizeof(*binfo_dat));
     *binfo_dat = binfo->bi_dat;
 }
 
 static const struct nilfs_sc_operations nilfs_sc_dat_ops = {
     .collect_data = nilfs_collect_dat_data,
     .collect_node = nilfs_collect_file_node,
     .collect_bmap = nilfs_collect_dat_bmap,
     .write_data_binfo = nilfs_write_dat_data_binfo,
     .write_node_binfo = nilfs_write_dat_node_binfo,
 };
 
 static const struct nilfs_sc_operations nilfs_sc_dsync_ops = {
     .collect_data = nilfs_collect_file_data,
     .collect_node = NULL,
     .collect_bmap = NULL,
     .write_data_binfo = nilfs_write_file_data_binfo,
     .write_node_binfo = NULL,
 };
 
 static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
                           struct list_head *listp,
                           size_t nlimit,
                           loff_t start, loff_t end)
 {
     struct address_space *mapping = inode->i_mapping;
     struct pagevec pvec;
     pgoff_t index = 0, last = ULONG_MAX;
     size_t ndirties = 0;
     int i;
 
     if (unlikely(start != 0 || end != LLONG_MAX)) {
         /*
          * A valid range is given for sync-ing data pages. The
          * range is rounded to per-page; extra dirty buffers
          * may be included if blocksize < pagesize.
          */
         index = start >> PAGE_SHIFT;
         last = end >> PAGE_SHIFT;
     }
     pagevec_init(&pvec);
  repeat:
     if (unlikely(index > last) ||
         !pagevec_lookup_range_tag(&pvec, mapping, &index, last,
                 PAGECACHE_TAG_DIRTY))
         return ndirties;
 
     for (i = 0; i < pagevec_count(&pvec); i++) {
         struct buffer_head *bh, *head;
         struct page *page = pvec.pages[i];
 
         lock_page(page);
         if (!page_has_buffers(page))
             create_empty_buffers(page, i_blocksize(inode), 0);
         unlock_page(page);
 
         bh = head = page_buffers(page);
         do {
             if (!buffer_dirty(bh) || buffer_async_write(bh))
                 continue;
             get_bh(bh);
             list_add_tail(&bh->b_assoc_buffers, listp);
             ndirties++;
             if (unlikely(ndirties >= nlimit)) {
                 pagevec_release(&pvec);
                 cond_resched();
                 return ndirties;
             }
         } while (bh = bh->b_this_page, bh != head);
     }
     pagevec_release(&pvec);
     cond_resched();
     goto repeat;
 }
 
 static void nilfs_lookup_dirty_node_buffers(struct inode *inode,
                         struct list_head *listp)
 {
     struct nilfs_inode_info *ii = NILFS_I(inode);
     struct inode *btnc_inode = ii->i_assoc_inode;
     struct pagevec pvec;
     struct buffer_head *bh, *head;
     unsigned int i;
     pgoff_t index = 0;
 
     if (!btnc_inode)
         return;
 
     pagevec_init(&pvec);
 
     while (pagevec_lookup_tag(&pvec, btnc_inode->i_mapping, &index,
                     PAGECACHE_TAG_DIRTY)) {
         for (i = 0; i < pagevec_count(&pvec); i++) {
             bh = head = page_buffers(pvec.pages[i]);
             do {
                 if (buffer_dirty(bh) &&
                         !buffer_async_write(bh)) {
                     get_bh(bh);
                     list_add_tail(&bh->b_assoc_buffers,
                               listp);
                 }
                 bh = bh->b_this_page;
             } while (bh != head);
         }
         pagevec_release(&pvec);
         cond_resched();
     }
 }
 
 static void nilfs_dispose_list(struct the_nilfs *nilfs,
                    struct list_head *head, int force)
 {
     struct nilfs_inode_info *ii, *n;
     struct nilfs_inode_info *ivec[SC_N_INODEVEC], **pii;
     unsigned int nv = 0;
 
     while (!list_empty(head)) {
         spin_lock(&nilfs->ns_inode_lock);
         list_for_each_entry_safe(ii, n, head, i_dirty) {
             list_del_init(&ii->i_dirty);
             if (force) {
                 if (unlikely(ii->i_bh)) {
                     brelse(ii->i_bh);
                     ii->i_bh = NULL;
                 }
             } else if (test_bit(NILFS_I_DIRTY, &ii->i_state)) {
                 set_bit(NILFS_I_QUEUED, &ii->i_state);
                 list_add_tail(&ii->i_dirty,
                           &nilfs->ns_dirty_files);
                 continue;
             }
             ivec[nv++] = ii;
             if (nv == SC_N_INODEVEC)
                 break;
         }
         spin_unlock(&nilfs->ns_inode_lock);
 
         for (pii = ivec; nv > 0; pii++, nv--)
             iput(&(*pii)->vfs_inode);
     }
 }
 
 static void nilfs_iput_work_func(struct work_struct *work)
 {
     struct nilfs_sc_info *sci = container_of(work, struct nilfs_sc_info,
                          sc_iput_work);
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
 
     nilfs_dispose_list(nilfs, &sci->sc_iput_queue, 0);
 }
 
 static int nilfs_test_metadata_dirty(struct the_nilfs *nilfs,
                      struct nilfs_root *root)
 {
     int ret = 0;
 
     if (nilfs_mdt_fetch_dirty(root->ifile))
         ret++;
     if (nilfs_mdt_fetch_dirty(nilfs->ns_cpfile))
         ret++;
     if (nilfs_mdt_fetch_dirty(nilfs->ns_sufile))
         ret++;
     if ((ret || nilfs_doing_gc()) && nilfs_mdt_fetch_dirty(nilfs->ns_dat))
         ret++;
     return ret;
 }
 
 static int nilfs_segctor_clean(struct nilfs_sc_info *sci)
 {
     return list_empty(&sci->sc_dirty_files) &&
         !test_bit(NILFS_SC_DIRTY, &sci->sc_flags) &&
         sci->sc_nfreesegs == 0 &&
         (!nilfs_doing_gc() || list_empty(&sci->sc_gc_inodes));
 }
 
 static int nilfs_segctor_confirm(struct nilfs_sc_info *sci)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     int ret = 0;
 
     if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
         set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
 
     spin_lock(&nilfs->ns_inode_lock);
     if (list_empty(&nilfs->ns_dirty_files) && nilfs_segctor_clean(sci))
         ret++;
 
     spin_unlock(&nilfs->ns_inode_lock);
     return ret;
 }
 
 static void nilfs_segctor_clear_metadata_dirty(struct nilfs_sc_info *sci)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
 
     nilfs_mdt_clear_dirty(sci->sc_root->ifile);
     nilfs_mdt_clear_dirty(nilfs->ns_cpfile);
     nilfs_mdt_clear_dirty(nilfs->ns_sufile);
     nilfs_mdt_clear_dirty(nilfs->ns_dat);
 }
 
 static int nilfs_segctor_create_checkpoint(struct nilfs_sc_info *sci)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     struct buffer_head *bh_cp;
     struct nilfs_checkpoint *raw_cp;
     int err;
 
     /* XXX: this interface will be changed */
     err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 1,
                       &raw_cp, &bh_cp);
     if (likely(!err)) {
         /*
          * The following code is duplicated with cpfile.  But, it is
          * needed to collect the checkpoint even if it was not newly
          * created.
          */
         mark_buffer_dirty(bh_cp);
         nilfs_mdt_mark_dirty(nilfs->ns_cpfile);
         nilfs_cpfile_put_checkpoint(
             nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
     } else
         WARN_ON(err == -EINVAL || err == -ENOENT);
 
     return err;
 }
 
 static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     struct buffer_head *bh_cp;
     struct nilfs_checkpoint *raw_cp;
     int err;
 
     err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 0,
                       &raw_cp, &bh_cp);
     if (unlikely(err)) {
         WARN_ON(err == -EINVAL || err == -ENOENT);
         goto failed_ibh;
     }
     raw_cp->cp_snapshot_list.ssl_next = 0;
     raw_cp->cp_snapshot_list.ssl_prev = 0;
     raw_cp->cp_inodes_count =
         cpu_to_le64(atomic64_read(&sci->sc_root->inodes_count));
     raw_cp->cp_blocks_count =
         cpu_to_le64(atomic64_read(&sci->sc_root->blocks_count));
     raw_cp->cp_nblk_inc =
         cpu_to_le64(sci->sc_nblk_inc + sci->sc_nblk_this_inc);
     raw_cp->cp_create = cpu_to_le64(sci->sc_seg_ctime);
     raw_cp->cp_cno = cpu_to_le64(nilfs->ns_cno);
 
     if (test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
         nilfs_checkpoint_clear_minor(raw_cp);
     else
         nilfs_checkpoint_set_minor(raw_cp);
 
     nilfs_write_inode_common(sci->sc_root->ifile,
                  &raw_cp->cp_ifile_inode, 1);
     nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
     return 0;
 
  failed_ibh:
     return err;
 }
 
 static void nilfs_fill_in_file_bmap(struct inode *ifile,
                     struct nilfs_inode_info *ii)
 
 {
     struct buffer_head *ibh;
     struct nilfs_inode *raw_inode;
 
     if (test_bit(NILFS_I_BMAP, &ii->i_state)) {
         ibh = ii->i_bh;
         BUG_ON(!ibh);
         raw_inode = nilfs_ifile_map_inode(ifile, ii->vfs_inode.i_ino,
                           ibh);
         nilfs_bmap_write(ii->i_bmap, raw_inode);
         nilfs_ifile_unmap_inode(ifile, ii->vfs_inode.i_ino, ibh);
     }
 }
 
 static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci)
 {
     struct nilfs_inode_info *ii;
 
     list_for_each_entry(ii, &sci->sc_dirty_files, i_dirty) {
         nilfs_fill_in_file_bmap(sci->sc_root->ifile, ii);
         set_bit(NILFS_I_COLLECTED, &ii->i_state);
     }
 }
 
 static void nilfs_segctor_fill_in_super_root(struct nilfs_sc_info *sci,
                          struct the_nilfs *nilfs)
 {
     struct buffer_head *bh_sr;
     struct nilfs_super_root *raw_sr;
     unsigned int isz, srsz;
 
     bh_sr = NILFS_LAST_SEGBUF(&sci->sc_segbufs)->sb_super_root;
     raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
     isz = nilfs->ns_inode_size;
     srsz = NILFS_SR_BYTES(isz);
 
     raw_sr->sr_bytes = cpu_to_le16(srsz);
     raw_sr->sr_nongc_ctime
         = cpu_to_le64(nilfs_doing_gc() ?
                   nilfs->ns_nongc_ctime : sci->sc_seg_ctime);
     raw_sr->sr_flags = 0;
 
     nilfs_write_inode_common(nilfs->ns_dat, (void *)raw_sr +
                  NILFS_SR_DAT_OFFSET(isz), 1);
     nilfs_write_inode_common(nilfs->ns_cpfile, (void *)raw_sr +
                  NILFS_SR_CPFILE_OFFSET(isz), 1);
     nilfs_write_inode_common(nilfs->ns_sufile, (void *)raw_sr +
                  NILFS_SR_SUFILE_OFFSET(isz), 1);
     memset((void *)raw_sr + srsz, 0, nilfs->ns_blocksize - srsz);
 }
 
 static void nilfs_redirty_inodes(struct list_head *head)
 {
     struct nilfs_inode_info *ii;
 
     list_for_each_entry(ii, head, i_dirty) {
         if (test_bit(NILFS_I_COLLECTED, &ii->i_state))
             clear_bit(NILFS_I_COLLECTED, &ii->i_state);
     }
 }
 
 static void nilfs_drop_collected_inodes(struct list_head *head)
 {
     struct nilfs_inode_info *ii;
 
     list_for_each_entry(ii, head, i_dirty) {
         if (!test_and_clear_bit(NILFS_I_COLLECTED, &ii->i_state))
             continue;
 
         clear_bit(NILFS_I_INODE_SYNC, &ii->i_state);
         set_bit(NILFS_I_UPDATED, &ii->i_state);
     }
 }
 
 static int nilfs_segctor_apply_buffers(struct nilfs_sc_info *sci,
                        struct inode *inode,
                        struct list_head *listp,
                        int (*collect)(struct nilfs_sc_info *,
                               struct buffer_head *,
                               struct inode *))
 {
     struct buffer_head *bh, *n;
     int err = 0;
 
     if (collect) {
         list_for_each_entry_safe(bh, n, listp, b_assoc_buffers) {
             list_del_init(&bh->b_assoc_buffers);
             err = collect(sci, bh, inode);
             brelse(bh);
             if (unlikely(err))
                 goto dispose_buffers;
         }
         return 0;
     }
 
  dispose_buffers:
     while (!list_empty(listp)) {
         bh = list_first_entry(listp, struct buffer_head,
                       b_assoc_buffers);
         list_del_init(&bh->b_assoc_buffers);
         brelse(bh);
     }
     return err;
 }
 
 static size_t nilfs_segctor_buffer_rest(struct nilfs_sc_info *sci)
 {
     /* Remaining number of blocks within segment buffer */
     return sci->sc_segbuf_nblocks -
         (sci->sc_nblk_this_inc + sci->sc_curseg->sb_sum.nblocks);
 }
 
 static int nilfs_segctor_scan_file(struct nilfs_sc_info *sci,
                    struct inode *inode,
                    const struct nilfs_sc_operations *sc_ops)
 {
     LIST_HEAD(data_buffers);
     LIST_HEAD(node_buffers);
     int err;
 
     if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {
         size_t n, rest = nilfs_segctor_buffer_rest(sci);
 
         n = nilfs_lookup_dirty_data_buffers(
             inode, &data_buffers, rest + 1, 0, LLONG_MAX);
         if (n > rest) {
             err = nilfs_segctor_apply_buffers(
                 sci, inode, &data_buffers,
                 sc_ops->collect_data);
             BUG_ON(!err); /* always receive -E2BIG or true error */
             goto break_or_fail;
         }
     }
     nilfs_lookup_dirty_node_buffers(inode, &node_buffers);
 
     if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {
         err = nilfs_segctor_apply_buffers(
             sci, inode, &data_buffers, sc_ops->collect_data);
         if (unlikely(err)) {
             /* dispose node list */
             nilfs_segctor_apply_buffers(
                 sci, inode, &node_buffers, NULL);
             goto break_or_fail;
         }
         sci->sc_stage.flags |= NILFS_CF_NODE;
     }
     /* Collect node */
     err = nilfs_segctor_apply_buffers(
         sci, inode, &node_buffers, sc_ops->collect_node);
     if (unlikely(err))
         goto break_or_fail;
 
     nilfs_bmap_lookup_dirty_buffers(NILFS_I(inode)->i_bmap, &node_buffers);
     err = nilfs_segctor_apply_buffers(
         sci, inode, &node_buffers, sc_ops->collect_bmap);
     if (unlikely(err))
         goto break_or_fail;
 
     nilfs_segctor_end_finfo(sci, inode);
     sci->sc_stage.flags &= ~NILFS_CF_NODE;
 
  break_or_fail:
     return err;
 }
 
 static int nilfs_segctor_scan_file_dsync(struct nilfs_sc_info *sci,
                      struct inode *inode)
 {
     LIST_HEAD(data_buffers);
     size_t n, rest = nilfs_segctor_buffer_rest(sci);
     int err;
 
     n = nilfs_lookup_dirty_data_buffers(inode, &data_buffers, rest + 1,
                         sci->sc_dsync_start,
                         sci->sc_dsync_end);
 
     err = nilfs_segctor_apply_buffers(sci, inode, &data_buffers,
                       nilfs_collect_file_data);
     if (!err) {
         nilfs_segctor_end_finfo(sci, inode);
         BUG_ON(n > rest);
         /* always receive -E2BIG or true error if n > rest */
     }
     return err;
 }
 
 static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     struct list_head *head;
     struct nilfs_inode_info *ii;
     size_t ndone;
     int err = 0;
 
     switch (nilfs_sc_cstage_get(sci)) {
     case NILFS_ST_INIT:
         /* Pre-processes */
         sci->sc_stage.flags = 0;
 
         if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags)) {
             sci->sc_nblk_inc = 0;
             sci->sc_curseg->sb_sum.flags = NILFS_SS_LOGBGN;
             if (mode == SC_LSEG_DSYNC) {
                 nilfs_sc_cstage_set(sci, NILFS_ST_DSYNC);
                 goto dsync_mode;
             }
         }
 
         sci->sc_stage.dirty_file_ptr = NULL;
         sci->sc_stage.gc_inode_ptr = NULL;
         if (mode == SC_FLUSH_DAT) {
             nilfs_sc_cstage_set(sci, NILFS_ST_DAT);
             goto dat_stage;
         }
         nilfs_sc_cstage_inc(sci);
         fallthrough;
     case NILFS_ST_GC:
         if (nilfs_doing_gc()) {
             head = &sci->sc_gc_inodes;
             ii = list_prepare_entry(sci->sc_stage.gc_inode_ptr,
                         head, i_dirty);
             list_for_each_entry_continue(ii, head, i_dirty) {
                 err = nilfs_segctor_scan_file(
                     sci, &ii->vfs_inode,
                     &nilfs_sc_file_ops);
                 if (unlikely(err)) {
                     sci->sc_stage.gc_inode_ptr = list_entry(
                         ii->i_dirty.prev,
                         struct nilfs_inode_info,
                         i_dirty);
                     goto break_or_fail;
                 }
                 set_bit(NILFS_I_COLLECTED, &ii->i_state);
             }
             sci->sc_stage.gc_inode_ptr = NULL;
         }
         nilfs_sc_cstage_inc(sci);
         fallthrough;
     case NILFS_ST_FILE:
         head = &sci->sc_dirty_files;
         ii = list_prepare_entry(sci->sc_stage.dirty_file_ptr, head,
                     i_dirty);
         list_for_each_entry_continue(ii, head, i_dirty) {
             clear_bit(NILFS_I_DIRTY, &ii->i_state);
 
             err = nilfs_segctor_scan_file(sci, &ii->vfs_inode,
                               &nilfs_sc_file_ops);
             if (unlikely(err)) {
                 sci->sc_stage.dirty_file_ptr =
                     list_entry(ii->i_dirty.prev,
                            struct nilfs_inode_info,
                            i_dirty);
                 goto break_or_fail;
             }
             /* sci->sc_stage.dirty_file_ptr = NILFS_I(inode); */
             /* XXX: required ? */
         }
         sci->sc_stage.dirty_file_ptr = NULL;
         if (mode == SC_FLUSH_FILE) {
             nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
             return 0;
         }
         nilfs_sc_cstage_inc(sci);
         sci->sc_stage.flags |= NILFS_CF_IFILE_STARTED;
         fallthrough;
     case NILFS_ST_IFILE:
         err = nilfs_segctor_scan_file(sci, sci->sc_root->ifile,
                           &nilfs_sc_file_ops);
         if (unlikely(err))
             break;
         nilfs_sc_cstage_inc(sci);
         /* Creating a checkpoint */
         err = nilfs_segctor_create_checkpoint(sci);
         if (unlikely(err))
             break;
         fallthrough;
     case NILFS_ST_CPFILE:
         err = nilfs_segctor_scan_file(sci, nilfs->ns_cpfile,
                           &nilfs_sc_file_ops);
         if (unlikely(err))
             break;
         nilfs_sc_cstage_inc(sci);
         fallthrough;
     case NILFS_ST_SUFILE:
         err = nilfs_sufile_freev(nilfs->ns_sufile, sci->sc_freesegs,
                      sci->sc_nfreesegs, &ndone);
         if (unlikely(err)) {
             nilfs_sufile_cancel_freev(nilfs->ns_sufile,
                           sci->sc_freesegs, ndone,
                           NULL);
             break;
         }
         sci->sc_stage.flags |= NILFS_CF_SUFREED;
 
         err = nilfs_segctor_scan_file(sci, nilfs->ns_sufile,
                           &nilfs_sc_file_ops);
         if (unlikely(err))
             break;
         nilfs_sc_cstage_inc(sci);
         fallthrough;
     case NILFS_ST_DAT:
  dat_stage:
         err = nilfs_segctor_scan_file(sci, nilfs->ns_dat,
                           &nilfs_sc_dat_ops);
         if (unlikely(err))
             break;
         if (mode == SC_FLUSH_DAT) {
             nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
             return 0;
         }
         nilfs_sc_cstage_inc(sci);
         fallthrough;
     case NILFS_ST_SR:
         if (mode == SC_LSEG_SR) {
             /* Appending a super root */
             err = nilfs_segctor_add_super_root(sci);
             if (unlikely(err))
                 break;
         }
         /* End of a logical segment */
         sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
         nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
         return 0;
     case NILFS_ST_DSYNC:
  dsync_mode:
         sci->sc_curseg->sb_sum.flags |= NILFS_SS_SYNDT;
         ii = sci->sc_dsync_inode;
         if (!test_bit(NILFS_I_BUSY, &ii->i_state))
             break;
 
         err = nilfs_segctor_scan_file_dsync(sci, &ii->vfs_inode);
         if (unlikely(err))
             break;
         sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
         nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
         return 0;
     case NILFS_ST_DONE:
         return 0;
     default:
         BUG();
     }
 
  break_or_fail:
     return err;
 }
 
 /**
  * nilfs_segctor_begin_construction - setup segment buffer to make a new log
  * @sci: nilfs_sc_info
  * @nilfs: nilfs object
  */
 static int nilfs_segctor_begin_construction(struct nilfs_sc_info *sci,
                         struct the_nilfs *nilfs)
 {
     struct nilfs_segment_buffer *segbuf, *prev;
     __u64 nextnum;
     int err, alloc = 0;
 
     segbuf = nilfs_segbuf_new(sci->sc_super);
     if (unlikely(!segbuf))
         return -ENOMEM;
 
     if (list_empty(&sci->sc_write_logs)) {
         nilfs_segbuf_map(segbuf, nilfs->ns_segnum,
                  nilfs->ns_pseg_offset, nilfs);
         if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
             nilfs_shift_to_next_segment(nilfs);
             nilfs_segbuf_map(segbuf, nilfs->ns_segnum, 0, nilfs);
         }
 
         segbuf->sb_sum.seg_seq = nilfs->ns_seg_seq;
         nextnum = nilfs->ns_nextnum;
 
         if (nilfs->ns_segnum == nilfs->ns_nextnum)
             /* Start from the head of a new full segment */
             alloc++;
     } else {
         /* Continue logs */
         prev = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
         nilfs_segbuf_map_cont(segbuf, prev);
         segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq;
         nextnum = prev->sb_nextnum;
 
         if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
             nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
             segbuf->sb_sum.seg_seq++;
             alloc++;
         }
     }
 
     err = nilfs_sufile_mark_dirty(nilfs->ns_sufile, segbuf->sb_segnum);
     if (err)
         goto failed;
 
     if (alloc) {
         err = nilfs_sufile_alloc(nilfs->ns_sufile, &nextnum);
         if (err)
             goto failed;
     }
     nilfs_segbuf_set_next_segnum(segbuf, nextnum, nilfs);
 
     BUG_ON(!list_empty(&sci->sc_segbufs));
     list_add_tail(&segbuf->sb_list, &sci->sc_segbufs);
     sci->sc_segbuf_nblocks = segbuf->sb_rest_blocks;
     return 0;
 
  failed:
     nilfs_segbuf_free(segbuf);
     return err;
 }
 
 static int nilfs_segctor_extend_segments(struct nilfs_sc_info *sci,
                      struct the_nilfs *nilfs, int nadd)
 {
     struct nilfs_segment_buffer *segbuf, *prev;
     struct inode *sufile = nilfs->ns_sufile;
     __u64 nextnextnum;
     LIST_HEAD(list);
     int err, ret, i;
 
     prev = NILFS_LAST_SEGBUF(&sci->sc_segbufs);
     /*
      * Since the segment specified with nextnum might be allocated during
      * the previous construction, the buffer including its segusage may
      * not be dirty.  The following call ensures that the buffer is dirty
      * and will pin the buffer on memory until the sufile is written.
      */
     err = nilfs_sufile_mark_dirty(sufile, prev->sb_nextnum);
     if (unlikely(err))
         return err;
 
     for (i = 0; i < nadd; i++) {
         /* extend segment info */
         err = -ENOMEM;
         segbuf = nilfs_segbuf_new(sci->sc_super);
         if (unlikely(!segbuf))
             goto failed;
 
         /* map this buffer to region of segment on-disk */
         nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
         sci->sc_segbuf_nblocks += segbuf->sb_rest_blocks;
 
         /* allocate the next next full segment */
         err = nilfs_sufile_alloc(sufile, &nextnextnum);
         if (unlikely(err))
             goto failed_segbuf;
 
         segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq + 1;
         nilfs_segbuf_set_next_segnum(segbuf, nextnextnum, nilfs);
 
         list_add_tail(&segbuf->sb_list, &list);
         prev = segbuf;
     }
     list_splice_tail(&list, &sci->sc_segbufs);
     return 0;
 
  failed_segbuf:
     nilfs_segbuf_free(segbuf);
  failed:
     list_for_each_entry(segbuf, &list, sb_list) {
         ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
         WARN_ON(ret); /* never fails */
     }
     nilfs_destroy_logs(&list);
     return err;
 }
 
 static void nilfs_free_incomplete_logs(struct list_head *logs,
                        struct the_nilfs *nilfs)
 {
     struct nilfs_segment_buffer *segbuf, *prev;
     struct inode *sufile = nilfs->ns_sufile;
     int ret;
 
     segbuf = NILFS_FIRST_SEGBUF(logs);
     if (nilfs->ns_nextnum != segbuf->sb_nextnum) {
         ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
         WARN_ON(ret); /* never fails */
     }
     if (atomic_read(&segbuf->sb_err)) {
         /* Case 1: The first segment failed */
         if (segbuf->sb_pseg_start != segbuf->sb_fseg_start)
             /*
              * Case 1a:  Partial segment appended into an existing
              * segment
              */
             nilfs_terminate_segment(nilfs, segbuf->sb_fseg_start,
                         segbuf->sb_fseg_end);
         else /* Case 1b:  New full segment */
             set_nilfs_discontinued(nilfs);
     }
 
     prev = segbuf;
     list_for_each_entry_continue(segbuf, logs, sb_list) {
         if (prev->sb_nextnum != segbuf->sb_nextnum) {
             ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
             WARN_ON(ret); /* never fails */
         }
         if (atomic_read(&segbuf->sb_err) &&
             segbuf->sb_segnum != nilfs->ns_nextnum)
             /* Case 2: extended segment (!= next) failed */
             nilfs_sufile_set_error(sufile, segbuf->sb_segnum);
         prev = segbuf;
     }
 }
 
 static void nilfs_segctor_update_segusage(struct nilfs_sc_info *sci,
                       struct inode *sufile)
 {
     struct nilfs_segment_buffer *segbuf;
     unsigned long live_blocks;
     int ret;
 
     list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
         live_blocks = segbuf->sb_sum.nblocks +
             (segbuf->sb_pseg_start - segbuf->sb_fseg_start);
         ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
                              live_blocks,
                              sci->sc_seg_ctime);
         WARN_ON(ret); /* always succeed because the segusage is dirty */
     }
 }
 
 static void nilfs_cancel_segusage(struct list_head *logs, struct inode *sufile)
 {
     struct nilfs_segment_buffer *segbuf;
     int ret;
 
     segbuf = NILFS_FIRST_SEGBUF(logs);
     ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
                          segbuf->sb_pseg_start -
                          segbuf->sb_fseg_start, 0);
     WARN_ON(ret); /* always succeed because the segusage is dirty */
 
     list_for_each_entry_continue(segbuf, logs, sb_list) {
         ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
                              0, 0);
         WARN_ON(ret); /* always succeed */
     }
 }
 
 static void nilfs_segctor_truncate_segments(struct nilfs_sc_info *sci,
                         struct nilfs_segment_buffer *last,
                         struct inode *sufile)
 {
     struct nilfs_segment_buffer *segbuf = last;
     int ret;
 
     list_for_each_entry_continue(segbuf, &sci->sc_segbufs, sb_list) {
         sci->sc_segbuf_nblocks -= segbuf->sb_rest_blocks;
         ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
         WARN_ON(ret);
     }
     nilfs_truncate_logs(&sci->sc_segbufs, last);
 }
 
 
 static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
                  struct the_nilfs *nilfs, int mode)
 {
     struct nilfs_cstage prev_stage = sci->sc_stage;
     int err, nadd = 1;
 
     /* Collection retry loop */
     for (;;) {
         sci->sc_nblk_this_inc = 0;
         sci->sc_curseg = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
 
         err = nilfs_segctor_reset_segment_buffer(sci);
         if (unlikely(err))
             goto failed;
 
         err = nilfs_segctor_collect_blocks(sci, mode);
         sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
         if (!err)
             break;
 
         if (unlikely(err != -E2BIG))
             goto failed;
 
         /* The current segment is filled up */
         if (mode != SC_LSEG_SR ||
             nilfs_sc_cstage_get(sci) < NILFS_ST_CPFILE)
             break;
 
         nilfs_clear_logs(&sci->sc_segbufs);
 
         if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
             err = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
                             sci->sc_freesegs,
                             sci->sc_nfreesegs,
                             NULL);
             WARN_ON(err); /* do not happen */
             sci->sc_stage.flags &= ~NILFS_CF_SUFREED;
         }
 
         err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
         if (unlikely(err))
             return err;
 
         nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
         sci->sc_stage = prev_stage;
     }
     nilfs_segctor_truncate_segments(sci, sci->sc_curseg, nilfs->ns_sufile);
     return 0;
 
  failed:
     return err;
 }
 
 static void nilfs_list_replace_buffer(struct buffer_head *old_bh,
                       struct buffer_head *new_bh)
 {
     BUG_ON(!list_empty(&new_bh->b_assoc_buffers));
 
     list_replace_init(&old_bh->b_assoc_buffers, &new_bh->b_assoc_buffers);
     /* The caller must release old_bh */
 }
 
 static int
 nilfs_segctor_update_payload_blocknr(struct nilfs_sc_info *sci,
                      struct nilfs_segment_buffer *segbuf,
                      int mode)
 {
     struct inode *inode = NULL;
     sector_t blocknr;
     unsigned long nfinfo = segbuf->sb_sum.nfinfo;
     unsigned long nblocks = 0, ndatablk = 0;
     const struct nilfs_sc_operations *sc_op = NULL;
     struct nilfs_segsum_pointer ssp;
     struct nilfs_finfo *finfo = NULL;
     union nilfs_binfo binfo;
     struct buffer_head *bh, *bh_org;
     ino_t ino = 0;
     int err = 0;
 
     if (!nfinfo)
         goto out;
 
     blocknr = segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk;
     ssp.bh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
     ssp.offset = sizeof(struct nilfs_segment_summary);
 
     list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
         if (bh == segbuf->sb_super_root)
             break;
         if (!finfo) {
             finfo = nilfs_segctor_map_segsum_entry(
                 sci, &ssp, sizeof(*finfo));
             ino = le64_to_cpu(finfo->fi_ino);
             nblocks = le32_to_cpu(finfo->fi_nblocks);
             ndatablk = le32_to_cpu(finfo->fi_ndatablk);
 
             inode = bh->b_page->mapping->host;
 
             if (mode == SC_LSEG_DSYNC)
                 sc_op = &nilfs_sc_dsync_ops;
             else if (ino == NILFS_DAT_INO)
                 sc_op = &nilfs_sc_dat_ops;
             else /* file blocks */
                 sc_op = &nilfs_sc_file_ops;
         }
         bh_org = bh;
         get_bh(bh_org);
         err = nilfs_bmap_assign(NILFS_I(inode)->i_bmap, &bh, blocknr,
                     &binfo);
         if (bh != bh_org)
             nilfs_list_replace_buffer(bh_org, bh);
         brelse(bh_org);
         if (unlikely(err))
             goto failed_bmap;
 
         if (ndatablk > 0)
             sc_op->write_data_binfo(sci, &ssp, &binfo);
         else
             sc_op->write_node_binfo(sci, &ssp, &binfo);
 
         blocknr++;
         if (--nblocks == 0) {
             finfo = NULL;
             if (--nfinfo == 0)
                 break;
         } else if (ndatablk > 0)
             ndatablk--;
     }
  out:
     return 0;
 
  failed_bmap:
     return err;
 }
 
 static int nilfs_segctor_assign(struct nilfs_sc_info *sci, int mode)
 {
     struct nilfs_segment_buffer *segbuf;
     int err;
 
     list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
         err = nilfs_segctor_update_payload_blocknr(sci, segbuf, mode);
         if (unlikely(err))
             return err;
         nilfs_segbuf_fill_in_segsum(segbuf);
     }
     return 0;
 }
 
 static void nilfs_begin_page_io(struct page *page)
 {
     if (!page || PageWriteback(page))
         /*
          * For split b-tree node pages, this function may be called
          * twice.  We ignore the 2nd or later calls by this check.
          */
         return;
 
     lock_page(page);
     clear_page_dirty_for_io(page);
     set_page_writeback(page);
     unlock_page(page);
 }
 
 static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)
 {
     struct nilfs_segment_buffer *segbuf;
     struct page *bd_page = NULL, *fs_page = NULL;
 
     list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
         struct buffer_head *bh;
 
         list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
                     b_assoc_buffers) {
             if (bh->b_page != bd_page) {
                 if (bd_page) {
                     lock_page(bd_page);
                     clear_page_dirty_for_io(bd_page);
                     set_page_writeback(bd_page);
                     unlock_page(bd_page);
                 }
                 bd_page = bh->b_page;
             }
         }
 
         list_for_each_entry(bh, &segbuf->sb_payload_buffers,
                     b_assoc_buffers) {
             set_buffer_async_write(bh);
             if (bh == segbuf->sb_super_root) {
                 if (bh->b_page != bd_page) {
                     lock_page(bd_page);
                     clear_page_dirty_for_io(bd_page);
                     set_page_writeback(bd_page);
                     unlock_page(bd_page);
                     bd_page = bh->b_page;
                 }
                 break;
             }
             if (bh->b_page != fs_page) {
                 nilfs_begin_page_io(fs_page);
                 fs_page = bh->b_page;
             }
         }
     }
     if (bd_page) {
         lock_page(bd_page);
         clear_page_dirty_for_io(bd_page);
         set_page_writeback(bd_page);
         unlock_page(bd_page);
     }
     nilfs_begin_page_io(fs_page);
 }
 
 static int nilfs_segctor_write(struct nilfs_sc_info *sci,
                    struct the_nilfs *nilfs)
 {
     int ret;
 
     ret = nilfs_write_logs(&sci->sc_segbufs, nilfs);
     list_splice_tail_init(&sci->sc_segbufs, &sci->sc_write_logs);
     return ret;
 }
 
 static void nilfs_end_page_io(struct page *page, int err)
 {
     if (!page)
         return;
 
     if (buffer_nilfs_node(page_buffers(page)) && !PageWriteback(page)) {
         /*
          * For b-tree node pages, this function may be called twice
          * or more because they might be split in a segment.
          */
         if (PageDirty(page)) {
             /*
              * For pages holding split b-tree node buffers, dirty
              * flag on the buffers may be cleared discretely.
              * In that case, the page is once redirtied for
              * remaining buffers, and it must be cancelled if
              * all the buffers get cleaned later.
              */
             lock_page(page);
             if (nilfs_page_buffers_clean(page))
                 __nilfs_clear_page_dirty(page);
             unlock_page(page);
         }
         return;
     }
 
     if (!err) {
         if (!nilfs_page_buffers_clean(page))
             __set_page_dirty_nobuffers(page);
         ClearPageError(page);
     } else {
         __set_page_dirty_nobuffers(page);
         SetPageError(page);
     }
 
     end_page_writeback(page);
 }
 
 static void nilfs_abort_logs(struct list_head *logs, int err)
 {
     struct nilfs_segment_buffer *segbuf;
     struct page *bd_page = NULL, *fs_page = NULL;
     struct buffer_head *bh;
 
     if (list_empty(logs))
         return;
 
     list_for_each_entry(segbuf, logs, sb_list) {
         list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
                     b_assoc_buffers) {
             if (bh->b_page != bd_page) {
                 if (bd_page)
                     end_page_writeback(bd_page);
                 bd_page = bh->b_page;
             }
         }
 
         list_for_each_entry(bh, &segbuf->sb_payload_buffers,
                     b_assoc_buffers) {
             clear_buffer_async_write(bh);
             if (bh == segbuf->sb_super_root) {
                 if (bh->b_page != bd_page) {
                     end_page_writeback(bd_page);
                     bd_page = bh->b_page;
                 }
                 break;
             }
             if (bh->b_page != fs_page) {
                 nilfs_end_page_io(fs_page, err);
                 fs_page = bh->b_page;
             }
         }
     }
     if (bd_page)
         end_page_writeback(bd_page);
 
     nilfs_end_page_io(fs_page, err);
 }
 
 static void nilfs_segctor_abort_construction(struct nilfs_sc_info *sci,
                          struct the_nilfs *nilfs, int err)
 {
     LIST_HEAD(logs);
     int ret;
 
     list_splice_tail_init(&sci->sc_write_logs, &logs);
     ret = nilfs_wait_on_logs(&logs);
     nilfs_abort_logs(&logs, ret ? : err);
 
     list_splice_tail_init(&sci->sc_segbufs, &logs);
     nilfs_cancel_segusage(&logs, nilfs->ns_sufile);
     nilfs_free_incomplete_logs(&logs, nilfs);
 
     if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
         ret = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
                         sci->sc_freesegs,
                         sci->sc_nfreesegs,
                         NULL);
         WARN_ON(ret); /* do not happen */
     }
 
     nilfs_destroy_logs(&logs);
 }
 
 static void nilfs_set_next_segment(struct the_nilfs *nilfs,
                    struct nilfs_segment_buffer *segbuf)
 {
     nilfs->ns_segnum = segbuf->sb_segnum;
     nilfs->ns_nextnum = segbuf->sb_nextnum;
     nilfs->ns_pseg_offset = segbuf->sb_pseg_start - segbuf->sb_fseg_start
         + segbuf->sb_sum.nblocks;
     nilfs->ns_seg_seq = segbuf->sb_sum.seg_seq;
     nilfs->ns_ctime = segbuf->sb_sum.ctime;
 }
 
 static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 {
     struct nilfs_segment_buffer *segbuf;
     struct page *bd_page = NULL, *fs_page = NULL;
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     int update_sr = false;
 
     list_for_each_entry(segbuf, &sci->sc_write_logs, sb_list) {
         struct buffer_head *bh;
 
         list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
                     b_assoc_buffers) {
             set_buffer_uptodate(bh);
             clear_buffer_dirty(bh);
             if (bh->b_page != bd_page) {
                 if (bd_page)
                     end_page_writeback(bd_page);
                 bd_page = bh->b_page;
             }
         }
         /*
          * We assume that the buffers which belong to the same page
          * continue over the buffer list.
          * Under this assumption, the last BHs of pages is
          * identifiable by the discontinuity of bh->b_page
          * (page != fs_page).
          *
          * For B-tree node blocks, however, this assumption is not
          * guaranteed.  The cleanup code of B-tree node pages needs
          * special care.
          */
         list_for_each_entry(bh, &segbuf->sb_payload_buffers,
                     b_assoc_buffers) {
             const unsigned long set_bits = BIT(BH_Uptodate);
             const unsigned long clear_bits =
                 (BIT(BH_Dirty) | BIT(BH_Async_Write) |
                  BIT(BH_Delay) | BIT(BH_NILFS_Volatile) |
                  BIT(BH_NILFS_Redirected));
 
             set_mask_bits(&bh->b_state, clear_bits, set_bits);
             if (bh == segbuf->sb_super_root) {
                 if (bh->b_page != bd_page) {
                     end_page_writeback(bd_page);
                     bd_page = bh->b_page;
                 }
                 update_sr = true;
                 break;
             }
             if (bh->b_page != fs_page) {
                 nilfs_end_page_io(fs_page, 0);
                 fs_page = bh->b_page;
             }
         }
 
         if (!nilfs_segbuf_simplex(segbuf)) {
             if (segbuf->sb_sum.flags & NILFS_SS_LOGBGN) {
                 set_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
                 sci->sc_lseg_stime = jiffies;
             }
             if (segbuf->sb_sum.flags & NILFS_SS_LOGEND)
                 clear_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
         }
     }
     /*
      * Since pages may continue over multiple segment buffers,
      * end of the last page must be checked outside of the loop.
      */
     if (bd_page)
         end_page_writeback(bd_page);
 
     nilfs_end_page_io(fs_page, 0);
 
     nilfs_drop_collected_inodes(&sci->sc_dirty_files);
 
     if (nilfs_doing_gc())
         nilfs_drop_collected_inodes(&sci->sc_gc_inodes);
     else
         nilfs->ns_nongc_ctime = sci->sc_seg_ctime;
 
     sci->sc_nblk_inc += sci->sc_nblk_this_inc;
 
     segbuf = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
     nilfs_set_next_segment(nilfs, segbuf);
 
     if (update_sr) {
         nilfs->ns_flushed_device = 0;
         nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
                        segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
 
         clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
         clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
         set_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
         nilfs_segctor_clear_metadata_dirty(sci);
     } else
         clear_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
 }
 
 static int nilfs_segctor_wait(struct nilfs_sc_info *sci)
 {
     int ret;
 
     ret = nilfs_wait_on_logs(&sci->sc_write_logs);
     if (!ret) {
         nilfs_segctor_complete_write(sci);
         nilfs_destroy_logs(&sci->sc_write_logs);
     }
     return ret;
 }
 
 static int nilfs_segctor_collect_dirty_files(struct nilfs_sc_info *sci,
                          struct the_nilfs *nilfs)
 {
     struct nilfs_inode_info *ii, *n;
     struct inode *ifile = sci->sc_root->ifile;
 
     spin_lock(&nilfs->ns_inode_lock);
  retry:
     list_for_each_entry_safe(ii, n, &nilfs->ns_dirty_files, i_dirty) {
         if (!ii->i_bh) {
             struct buffer_head *ibh;
             int err;
 
             spin_unlock(&nilfs->ns_inode_lock);
             err = nilfs_ifile_get_inode_block(
                 ifile, ii->vfs_inode.i_ino, &ibh);
             if (unlikely(err)) {
                 nilfs_warn(sci->sc_super,
                        "log writer: error %d getting inode block (ino=%lu)",
                        err, ii->vfs_inode.i_ino);
                 return err;
             }
             spin_lock(&nilfs->ns_inode_lock);
             if (likely(!ii->i_bh))
                 ii->i_bh = ibh;
             else
                 brelse(ibh);
             goto retry;
         }
 
         // Always redirty the buffer to avoid race condition
         mark_buffer_dirty(ii->i_bh);
         nilfs_mdt_mark_dirty(ifile);
 
         clear_bit(NILFS_I_QUEUED, &ii->i_state);
         set_bit(NILFS_I_BUSY, &ii->i_state);
         list_move_tail(&ii->i_dirty, &sci->sc_dirty_files);
     }
     spin_unlock(&nilfs->ns_inode_lock);
 
     return 0;
 }
 
 static void nilfs_segctor_drop_written_files(struct nilfs_sc_info *sci,
                          struct the_nilfs *nilfs)
 {
     struct nilfs_inode_info *ii, *n;
     int during_mount = !(sci->sc_super->s_flags & SB_ACTIVE);
     int defer_iput = false;
 
     spin_lock(&nilfs->ns_inode_lock);
     list_for_each_entry_safe(ii, n, &sci->sc_dirty_files, i_dirty) {
         if (!test_and_clear_bit(NILFS_I_UPDATED, &ii->i_state) ||
             test_bit(NILFS_I_DIRTY, &ii->i_state))
             continue;
 
         clear_bit(NILFS_I_BUSY, &ii->i_state);
         brelse(ii->i_bh);
         ii->i_bh = NULL;
         list_del_init(&ii->i_dirty);
         if (!ii->vfs_inode.i_nlink || during_mount) {
             /*
              * Defer calling iput() to avoid deadlocks if
              * i_nlink == 0 or mount is not yet finished.
              */
             list_add_tail(&ii->i_dirty, &sci->sc_iput_queue);
             defer_iput = true;
         } else {
             spin_unlock(&nilfs->ns_inode_lock);
             iput(&ii->vfs_inode);
             spin_lock(&nilfs->ns_inode_lock);
         }
     }
     spin_unlock(&nilfs->ns_inode_lock);
 
     if (defer_iput)
         schedule_work(&sci->sc_iput_work);
 }
 
 /*
  * Main procedure of segment constructor
  */
 static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     int err;
 
     nilfs_sc_cstage_set(sci, NILFS_ST_INIT);
     sci->sc_cno = nilfs->ns_cno;
 
     err = nilfs_segctor_collect_dirty_files(sci, nilfs);
     if (unlikely(err))
         goto out;
 
     if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
         set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
 
     if (nilfs_segctor_clean(sci))
         goto out;
 
     do {
         sci->sc_stage.flags &= ~NILFS_CF_HISTORY_MASK;
 
         err = nilfs_segctor_begin_construction(sci, nilfs);
         if (unlikely(err))
             goto out;
 
         /* Update time stamp */
         sci->sc_seg_ctime = ktime_get_real_seconds();
 
         err = nilfs_segctor_collect(sci, nilfs, mode);
         if (unlikely(err))
             goto failed;
 
         /* Avoid empty segment */
         if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE &&
             nilfs_segbuf_empty(sci->sc_curseg)) {
             nilfs_segctor_abort_construction(sci, nilfs, 1);
             goto out;
         }
 
         err = nilfs_segctor_assign(sci, mode);
         if (unlikely(err))
             goto failed;
 
         if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
             nilfs_segctor_fill_in_file_bmap(sci);
 
         if (mode == SC_LSEG_SR &&
             nilfs_sc_cstage_get(sci) >= NILFS_ST_CPFILE) {
             err = nilfs_segctor_fill_in_checkpoint(sci);
             if (unlikely(err))
                 goto failed_to_write;
 
             nilfs_segctor_fill_in_super_root(sci, nilfs);
         }
         nilfs_segctor_update_segusage(sci, nilfs->ns_sufile);
 
         /* Write partial segments */
         nilfs_segctor_prepare_write(sci);
 
         nilfs_add_checksums_on_logs(&sci->sc_segbufs,
                         nilfs->ns_crc_seed);
 
         err = nilfs_segctor_write(sci, nilfs);
         if (unlikely(err))
             goto failed_to_write;
 
         if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE ||
             nilfs->ns_blocksize_bits != PAGE_SHIFT) {
             /*
              * At this point, we avoid double buffering
              * for blocksize < pagesize because page dirty
              * flag is turned off during write and dirty
              * buffers are not properly collected for
              * pages crossing over segments.
              */
             err = nilfs_segctor_wait(sci);
             if (err)
                 goto failed_to_write;
         }
     } while (nilfs_sc_cstage_get(sci) != NILFS_ST_DONE);
 
  out:
     nilfs_segctor_drop_written_files(sci, nilfs);
     return err;
 
  failed_to_write:
     if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
         nilfs_redirty_inodes(&sci->sc_dirty_files);
 
  failed:
     if (nilfs_doing_gc())
         nilfs_redirty_inodes(&sci->sc_gc_inodes);
     nilfs_segctor_abort_construction(sci, nilfs, err);
     goto out;
 }
 
 /**
  * nilfs_segctor_start_timer - set timer of background write
  * @sci: nilfs_sc_info
  *
  * If the timer has already been set, it ignores the new request.
  * This function MUST be called within a section locking the segment
  * semaphore.
  */
 static void nilfs_segctor_start_timer(struct nilfs_sc_info *sci)
 {
     spin_lock(&sci->sc_state_lock);
     if (!(sci->sc_state & NILFS_SEGCTOR_COMMIT)) {
         sci->sc_timer.expires = jiffies + sci->sc_interval;
         add_timer(&sci->sc_timer);
         sci->sc_state |= NILFS_SEGCTOR_COMMIT;
     }
     spin_unlock(&sci->sc_state_lock);
 }
 
 static void nilfs_segctor_do_flush(struct nilfs_sc_info *sci, int bn)
 {
     spin_lock(&sci->sc_state_lock);
     if (!(sci->sc_flush_request & BIT(bn))) {
         unsigned long prev_req = sci->sc_flush_request;
 
         sci->sc_flush_request |= BIT(bn);
         if (!prev_req)
             wake_up(&sci->sc_wait_daemon);
     }
     spin_unlock(&sci->sc_state_lock);
 }
 
 /**
  * nilfs_flush_segment - trigger a segment construction for resource control
  * @sb: super block
  * @ino: inode number of the file to be flushed out.
  */
 void nilfs_flush_segment(struct super_block *sb, ino_t ino)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     struct nilfs_sc_info *sci = nilfs->ns_writer;
 
     if (!sci || nilfs_doing_construction())
         return;
     nilfs_segctor_do_flush(sci, NILFS_MDT_INODE(sb, ino) ? ino : 0);
                     /* assign bit 0 to data files */
 }
 
 struct nilfs_segctor_wait_request {
     wait_queue_entry_t  wq;
     __u32       seq;
     int     err;
     atomic_t    done;
 };
 
 static int nilfs_segctor_sync(struct nilfs_sc_info *sci)
 {
     struct nilfs_segctor_wait_request wait_req;
     int err = 0;
 
     spin_lock(&sci->sc_state_lock);
     init_wait(&wait_req.wq);
     wait_req.err = 0;
     atomic_set(&wait_req.done, 0);
     wait_req.seq = ++sci->sc_seq_request;
     spin_unlock(&sci->sc_state_lock);
 
     init_waitqueue_entry(&wait_req.wq, current);
     add_wait_queue(&sci->sc_wait_request, &wait_req.wq);
     set_current_state(TASK_INTERRUPTIBLE);
     wake_up(&sci->sc_wait_daemon);
 
     for (;;) {
         if (atomic_read(&wait_req.done)) {
             err = wait_req.err;
             break;
         }
         if (!signal_pending(current)) {
             schedule();
             continue;
         }
         err = -ERESTARTSYS;
         break;
     }
     finish_wait(&sci->sc_wait_request, &wait_req.wq);
     return err;
 }
 
 static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err)
 {
     struct nilfs_segctor_wait_request *wrq, *n;
     unsigned long flags;
 
     spin_lock_irqsave(&sci->sc_wait_request.lock, flags);
     list_for_each_entry_safe(wrq, n, &sci->sc_wait_request.head, wq.entry) {
         if (!atomic_read(&wrq->done) &&
             nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq)) {
             wrq->err = err;
             atomic_set(&wrq->done, 1);
         }
         if (atomic_read(&wrq->done)) {
             wrq->wq.func(&wrq->wq,
                      TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
                      0, NULL);
         }
     }
     spin_unlock_irqrestore(&sci->sc_wait_request.lock, flags);
 }
 
 /**
  * nilfs_construct_segment - construct a logical segment
  * @sb: super block
  *
  * Return Value: On success, 0 is returned. On errors, one of the following
  * negative error code is returned.
  *
  * %-EROFS - Read only filesystem.
  *
  * %-EIO - I/O error
  *
  * %-ENOSPC - No space left on device (only in a panic state).
  *
  * %-ERESTARTSYS - Interrupted.
  *
  * %-ENOMEM - Insufficient memory available.
  */
 int nilfs_construct_segment(struct super_block *sb)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     struct nilfs_sc_info *sci = nilfs->ns_writer;
     struct nilfs_transaction_info *ti;
     int err;
 
     if (!sci)
         return -EROFS;
 
     /* A call inside transactions causes a deadlock. */
     BUG_ON((ti = current->journal_info) && ti->ti_magic == NILFS_TI_MAGIC);
 
     err = nilfs_segctor_sync(sci);
     return err;
 }
 
 /**
  * nilfs_construct_dsync_segment - construct a data-only logical segment
  * @sb: super block
  * @inode: inode whose data blocks should be written out
  * @start: start byte offset
  * @end: end byte offset (inclusive)
  *
  * Return Value: On success, 0 is returned. On errors, one of the following
  * negative error code is returned.
  *
  * %-EROFS - Read only filesystem.
  *
  * %-EIO - I/O error
  *
  * %-ENOSPC - No space left on device (only in a panic state).
  *
  * %-ERESTARTSYS - Interrupted.
  *
  * %-ENOMEM - Insufficient memory available.
  */
 int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
                   loff_t start, loff_t end)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     struct nilfs_sc_info *sci = nilfs->ns_writer;
     struct nilfs_inode_info *ii;
     struct nilfs_transaction_info ti;
     int err = 0;
 
     if (!sci)
         return -EROFS;
 
     nilfs_transaction_lock(sb, &ti, 0);
 
     ii = NILFS_I(inode);
     if (test_bit(NILFS_I_INODE_SYNC, &ii->i_state) ||
         nilfs_test_opt(nilfs, STRICT_ORDER) ||
         test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
         nilfs_discontinued(nilfs)) {
         nilfs_transaction_unlock(sb);
         err = nilfs_segctor_sync(sci);
         return err;
     }
 
     spin_lock(&nilfs->ns_inode_lock);
     if (!test_bit(NILFS_I_QUEUED, &ii->i_state) &&
         !test_bit(NILFS_I_BUSY, &ii->i_state)) {
         spin_unlock(&nilfs->ns_inode_lock);
         nilfs_transaction_unlock(sb);
         return 0;
     }
     spin_unlock(&nilfs->ns_inode_lock);
     sci->sc_dsync_inode = ii;
     sci->sc_dsync_start = start;
     sci->sc_dsync_end = end;
 
     err = nilfs_segctor_do_construct(sci, SC_LSEG_DSYNC);
     if (!err)
         nilfs->ns_flushed_device = 0;
 
     nilfs_transaction_unlock(sb);
     return err;
 }
 
 #define FLUSH_FILE_BIT  (0x1) /* data file only */
 #define FLUSH_DAT_BIT   BIT(NILFS_DAT_INO) /* DAT only */
 
 /**
  * nilfs_segctor_accept - record accepted sequence count of log-write requests
  * @sci: segment constructor object
  */
 static void nilfs_segctor_accept(struct nilfs_sc_info *sci)
 {
     spin_lock(&sci->sc_state_lock);
     sci->sc_seq_accepted = sci->sc_seq_request;
     spin_unlock(&sci->sc_state_lock);
     del_timer_sync(&sci->sc_timer);
 }
 
 /**
  * nilfs_segctor_notify - notify the result of request to caller threads
  * @sci: segment constructor object
  * @mode: mode of log forming
  * @err: error code to be notified
  */
 static void nilfs_segctor_notify(struct nilfs_sc_info *sci, int mode, int err)
 {
     /* Clear requests (even when the construction failed) */
     spin_lock(&sci->sc_state_lock);
 
     if (mode == SC_LSEG_SR) {
         sci->sc_state &= ~NILFS_SEGCTOR_COMMIT;
         sci->sc_seq_done = sci->sc_seq_accepted;
         nilfs_segctor_wakeup(sci, err);
         sci->sc_flush_request = 0;
     } else {
         if (mode == SC_FLUSH_FILE)
             sci->sc_flush_request &= ~FLUSH_FILE_BIT;
         else if (mode == SC_FLUSH_DAT)
             sci->sc_flush_request &= ~FLUSH_DAT_BIT;
 
         /* re-enable timer if checkpoint creation was not done */
         if ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
             time_before(jiffies, sci->sc_timer.expires))
             add_timer(&sci->sc_timer);
     }
     spin_unlock(&sci->sc_state_lock);
 }
 
 /**
  * nilfs_segctor_construct - form logs and write them to disk
  * @sci: segment constructor object
  * @mode: mode of log forming
  */
 static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     struct nilfs_super_block **sbp;
     int err = 0;
 
     nilfs_segctor_accept(sci);
 
     if (nilfs_discontinued(nilfs))
         mode = SC_LSEG_SR;
     if (!nilfs_segctor_confirm(sci))
         err = nilfs_segctor_do_construct(sci, mode);
 
     if (likely(!err)) {
         if (mode != SC_FLUSH_DAT)
             atomic_set(&nilfs->ns_ndirtyblks, 0);
         if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) &&
             nilfs_discontinued(nilfs)) {
             down_write(&nilfs->ns_sem);
             err = -EIO;
             sbp = nilfs_prepare_super(sci->sc_super,
                           nilfs_sb_will_flip(nilfs));
             if (likely(sbp)) {
                 nilfs_set_log_cursor(sbp[0], nilfs);
                 err = nilfs_commit_super(sci->sc_super,
                              NILFS_SB_COMMIT);
             }
             up_write(&nilfs->ns_sem);
         }
     }
 
     nilfs_segctor_notify(sci, mode, err);
     return err;
 }
 
 static void nilfs_construction_timeout(struct timer_list *t)
 {
     struct nilfs_sc_info *sci = from_timer(sci, t, sc_timer);
 
     wake_up_process(sci->sc_timer_task);
 }
 
 static void
 nilfs_remove_written_gcinodes(struct the_nilfs *nilfs, struct list_head *head)
 {
     struct nilfs_inode_info *ii, *n;
 
     list_for_each_entry_safe(ii, n, head, i_dirty) {
         if (!test_bit(NILFS_I_UPDATED, &ii->i_state))
             continue;
         list_del_init(&ii->i_dirty);
         truncate_inode_pages(&ii->vfs_inode.i_data, 0);
         nilfs_btnode_cache_clear(ii->i_assoc_inode->i_mapping);
         iput(&ii->vfs_inode);
     }
 }
 
 int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
              void **kbufs)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     struct nilfs_sc_info *sci = nilfs->ns_writer;
     struct nilfs_transaction_info ti;
     int err;
 
     if (unlikely(!sci))
         return -EROFS;
 
     nilfs_transaction_lock(sb, &ti, 1);
 
     err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat);
     if (unlikely(err))
         goto out_unlock;
 
     err = nilfs_ioctl_prepare_clean_segments(nilfs, argv, kbufs);
     if (unlikely(err)) {
         nilfs_mdt_restore_from_shadow_map(nilfs->ns_dat);
         goto out_unlock;
     }
 
     sci->sc_freesegs = kbufs[4];
     sci->sc_nfreesegs = argv[4].v_nmembs;
     list_splice_tail_init(&nilfs->ns_gc_inodes, &sci->sc_gc_inodes);
 
     for (;;) {
         err = nilfs_segctor_construct(sci, SC_LSEG_SR);
         nilfs_remove_written_gcinodes(nilfs, &sci->sc_gc_inodes);
 
         if (likely(!err))
             break;
 
         nilfs_warn(sb, "error %d cleaning segments", err);
         set_current_state(TASK_INTERRUPTIBLE);
         schedule_timeout(sci->sc_interval);
     }
     if (nilfs_test_opt(nilfs, DISCARD)) {
         int ret = nilfs_discard_segments(nilfs, sci->sc_freesegs,
                          sci->sc_nfreesegs);
         if (ret) {
             nilfs_warn(sb,
                    "error %d on discard request, turning discards off for the device",
                    ret);
             nilfs_clear_opt(nilfs, DISCARD);
         }
     }
 
  out_unlock:
     sci->sc_freesegs = NULL;
     sci->sc_nfreesegs = 0;
     nilfs_mdt_clear_shadow_map(nilfs->ns_dat);
     nilfs_transaction_unlock(sb);
     return err;
 }
 
 static void nilfs_segctor_thread_construct(struct nilfs_sc_info *sci, int mode)
 {
     struct nilfs_transaction_info ti;
 
     nilfs_transaction_lock(sci->sc_super, &ti, 0);
     nilfs_segctor_construct(sci, mode);
 
     /*
      * Unclosed segment should be retried.  We do this using sc_timer.
      * Timeout of sc_timer will invoke complete construction which leads
      * to close the current logical segment.
      */
     if (test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags))
         nilfs_segctor_start_timer(sci);
 
     nilfs_transaction_unlock(sci->sc_super);
 }
 
 static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *sci)
 {
     int mode = 0;
 
     spin_lock(&sci->sc_state_lock);
     mode = (sci->sc_flush_request & FLUSH_DAT_BIT) ?
         SC_FLUSH_DAT : SC_FLUSH_FILE;
     spin_unlock(&sci->sc_state_lock);
 
     if (mode) {
         nilfs_segctor_do_construct(sci, mode);
 
         spin_lock(&sci->sc_state_lock);
         sci->sc_flush_request &= (mode == SC_FLUSH_FILE) ?
             ~FLUSH_FILE_BIT : ~FLUSH_DAT_BIT;
         spin_unlock(&sci->sc_state_lock);
     }
     clear_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
 }
 
 static int nilfs_segctor_flush_mode(struct nilfs_sc_info *sci)
 {
     if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
         time_before(jiffies, sci->sc_lseg_stime + sci->sc_mjcp_freq)) {
         if (!(sci->sc_flush_request & ~FLUSH_FILE_BIT))
             return SC_FLUSH_FILE;
         else if (!(sci->sc_flush_request & ~FLUSH_DAT_BIT))
             return SC_FLUSH_DAT;
     }
     return SC_LSEG_SR;
 }
 
 /**
  * nilfs_segctor_thread - main loop of the segment constructor thread.
  * @arg: pointer to a struct nilfs_sc_info.
  *
  * nilfs_segctor_thread() initializes a timer and serves as a daemon
  * to execute segment constructions.
  */
 static int nilfs_segctor_thread(void *arg)
 {
     struct nilfs_sc_info *sci = (struct nilfs_sc_info *)arg;
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     int timeout = 0;
 
     sci->sc_timer_task = current;
 
     /* start sync. */
     sci->sc_task = current;
     wake_up(&sci->sc_wait_task); /* for nilfs_segctor_start_thread() */
     nilfs_info(sci->sc_super,
            "segctord starting. Construction interval = %lu seconds, CP frequency < %lu seconds",
            sci->sc_interval / HZ, sci->sc_mjcp_freq / HZ);
 
     spin_lock(&sci->sc_state_lock);
  loop:
     for (;;) {
         int mode;
 
         if (sci->sc_state & NILFS_SEGCTOR_QUIT)
             goto end_thread;
 
         if (timeout || sci->sc_seq_request != sci->sc_seq_done)
             mode = SC_LSEG_SR;
         else if (sci->sc_flush_request)
             mode = nilfs_segctor_flush_mode(sci);
         else
             break;
 
         spin_unlock(&sci->sc_state_lock);
         nilfs_segctor_thread_construct(sci, mode);
         spin_lock(&sci->sc_state_lock);
         timeout = 0;
     }
 
 
     if (freezing(current)) {
         spin_unlock(&sci->sc_state_lock);
         try_to_freeze();
         spin_lock(&sci->sc_state_lock);
     } else {
         DEFINE_WAIT(wait);
         int should_sleep = 1;
 
         prepare_to_wait(&sci->sc_wait_daemon, &wait,
                 TASK_INTERRUPTIBLE);
 
         if (sci->sc_seq_request != sci->sc_seq_done)
             should_sleep = 0;
         else if (sci->sc_flush_request)
             should_sleep = 0;
         else if (sci->sc_state & NILFS_SEGCTOR_COMMIT)
             should_sleep = time_before(jiffies,
                     sci->sc_timer.expires);
 
         if (should_sleep) {
             spin_unlock(&sci->sc_state_lock);
             schedule();
             spin_lock(&sci->sc_state_lock);
         }
         finish_wait(&sci->sc_wait_daemon, &wait);
         timeout = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
                time_after_eq(jiffies, sci->sc_timer.expires));
 
         if (nilfs_sb_dirty(nilfs) && nilfs_sb_need_update(nilfs))
             set_nilfs_discontinued(nilfs);
     }
     goto loop;
 
  end_thread:
     spin_unlock(&sci->sc_state_lock);
 
     /* end sync. */
     sci->sc_task = NULL;
     wake_up(&sci->sc_wait_task); /* for nilfs_segctor_kill_thread() */
     return 0;
 }
 
 static int nilfs_segctor_start_thread(struct nilfs_sc_info *sci)
 {
     struct task_struct *t;
 
     t = kthread_run(nilfs_segctor_thread, sci, "segctord");
     if (IS_ERR(t)) {
         int err = PTR_ERR(t);
 
         nilfs_err(sci->sc_super, "error %d creating segctord thread",
               err);
         return err;
     }
     wait_event(sci->sc_wait_task, sci->sc_task != NULL);
     return 0;
 }
 
 static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
     __acquires(&sci->sc_state_lock)
     __releases(&sci->sc_state_lock)
 {
     sci->sc_state |= NILFS_SEGCTOR_QUIT;
 
     while (sci->sc_task) {
         wake_up(&sci->sc_wait_daemon);
         spin_unlock(&sci->sc_state_lock);
         wait_event(sci->sc_wait_task, sci->sc_task == NULL);
         spin_lock(&sci->sc_state_lock);
     }
 }
 
 /*
  * Setup & clean-up functions
  */
 static struct nilfs_sc_info *nilfs_segctor_new(struct super_block *sb,
                            struct nilfs_root *root)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     struct nilfs_sc_info *sci;
 
     sci = kzalloc(sizeof(*sci), GFP_KERNEL);
     if (!sci)
         return NULL;
 
     sci->sc_super = sb;
 
     nilfs_get_root(root);
     sci->sc_root = root;
 
     init_waitqueue_head(&sci->sc_wait_request);
     init_waitqueue_head(&sci->sc_wait_daemon);
     init_waitqueue_head(&sci->sc_wait_task);
     spin_lock_init(&sci->sc_state_lock);
     INIT_LIST_HEAD(&sci->sc_dirty_files);
     INIT_LIST_HEAD(&sci->sc_segbufs);
     INIT_LIST_HEAD(&sci->sc_write_logs);
     INIT_LIST_HEAD(&sci->sc_gc_inodes);
     INIT_LIST_HEAD(&sci->sc_iput_queue);
     INIT_WORK(&sci->sc_iput_work, nilfs_iput_work_func);
     timer_setup(&sci->sc_timer, nilfs_construction_timeout, 0);
 
     sci->sc_interval = HZ * NILFS_SC_DEFAULT_TIMEOUT;
     sci->sc_mjcp_freq = HZ * NILFS_SC_DEFAULT_SR_FREQ;
     sci->sc_watermark = NILFS_SC_DEFAULT_WATERMARK;
 
     if (nilfs->ns_interval)
         sci->sc_interval = HZ * nilfs->ns_interval;
     if (nilfs->ns_watermark)
         sci->sc_watermark = nilfs->ns_watermark;
     return sci;
 }
 
 static void nilfs_segctor_write_out(struct nilfs_sc_info *sci)
 {
     int ret, retrycount = NILFS_SC_CLEANUP_RETRY;
 
     /*
      * The segctord thread was stopped and its timer was removed.
      * But some tasks remain.
      */
     do {
         struct nilfs_transaction_info ti;
 
         nilfs_transaction_lock(sci->sc_super, &ti, 0);
         ret = nilfs_segctor_construct(sci, SC_LSEG_SR);
         nilfs_transaction_unlock(sci->sc_super);
 
         flush_work(&sci->sc_iput_work);
 
     } while (ret && retrycount-- > 0);
 }
 
 /**
  * nilfs_segctor_destroy - destroy the segment constructor.
  * @sci: nilfs_sc_info
  *
  * nilfs_segctor_destroy() kills the segctord thread and frees
  * the nilfs_sc_info struct.
  * Caller must hold the segment semaphore.
  */
 static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
 {
     struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
     int flag;
 
     up_write(&nilfs->ns_segctor_sem);
 
     spin_lock(&sci->sc_state_lock);
     nilfs_segctor_kill_thread(sci);
     flag = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) || sci->sc_flush_request
         || sci->sc_seq_request != sci->sc_seq_done);
     spin_unlock(&sci->sc_state_lock);
 
     if (flush_work(&sci->sc_iput_work))
         flag = true;
 
     if (flag || !nilfs_segctor_confirm(sci))
         nilfs_segctor_write_out(sci);
 
     if (!list_empty(&sci->sc_dirty_files)) {
         nilfs_warn(sci->sc_super,
                "disposed unprocessed dirty file(s) when stopping log writer");
         nilfs_dispose_list(nilfs, &sci->sc_dirty_files, 1);
     }
 
     if (!list_empty(&sci->sc_iput_queue)) {
         nilfs_warn(sci->sc_super,
                "disposed unprocessed inode(s) in iput queue when stopping log writer");
         nilfs_dispose_list(nilfs, &sci->sc_iput_queue, 1);
     }
 
     WARN_ON(!list_empty(&sci->sc_segbufs));
     WARN_ON(!list_empty(&sci->sc_write_logs));
 
     nilfs_put_root(sci->sc_root);
 
     down_write(&nilfs->ns_segctor_sem);
 
     del_timer_sync(&sci->sc_timer);
     kfree(sci);
 }
 
 /**
  * nilfs_attach_log_writer - attach log writer
  * @sb: super block instance
  * @root: root object of the current filesystem tree
  *
  * This allocates a log writer object, initializes it, and starts the
  * log writer.
  *
  * Return Value: On success, 0 is returned. On error, one of the following
  * negative error code is returned.
  *
  * %-ENOMEM - Insufficient memory available.
  */
 int nilfs_attach_log_writer(struct super_block *sb, struct nilfs_root *root)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     int err;
 
     if (nilfs->ns_writer) {
         /*
          * This happens if the filesystem was remounted
          * read/write after nilfs_error degenerated it into a
          * read-only mount.
          */
         nilfs_detach_log_writer(sb);
     }
 
     nilfs->ns_writer = nilfs_segctor_new(sb, root);
     if (!nilfs->ns_writer)
         return -ENOMEM;
 
     inode_attach_wb(nilfs->ns_bdev->bd_inode, NULL);
 
     err = nilfs_segctor_start_thread(nilfs->ns_writer);
     if (err) {
         kfree(nilfs->ns_writer);
         nilfs->ns_writer = NULL;
     }
     return err;
 }
 
 /**
  * nilfs_detach_log_writer - destroy log writer
  * @sb: super block instance
  *
  * This kills log writer daemon, frees the log writer object, and
  * destroys list of dirty files.
  */
 void nilfs_detach_log_writer(struct super_block *sb)
 {
     struct the_nilfs *nilfs = sb->s_fs_info;
     LIST_HEAD(garbage_list);
 
     down_write(&nilfs->ns_segctor_sem);
     if (nilfs->ns_writer) {
         nilfs_segctor_destroy(nilfs->ns_writer);
         nilfs->ns_writer = NULL;
     }
 
     /* Force to free the list of dirty files */
     spin_lock(&nilfs->ns_inode_lock);
     if (!list_empty(&nilfs->ns_dirty_files)) {
         list_splice_init(&nilfs->ns_dirty_files, &garbage_list);
         nilfs_warn(sb,
                "disposed unprocessed dirty file(s) when detaching log writer");
     }
     spin_unlock(&nilfs->ns_inode_lock);
     up_write(&nilfs->ns_segctor_sem);
 
     nilfs_dispose_list(nilfs, &garbage_list, 1);
 }