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 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * uptodate.c
  *
  * Tracking the up-to-date-ness of a local buffer_head with respect to
  * the cluster.
  *
  * Copyright (C) 2002, 2004, 2005 Oracle.  All rights reserved.
  *
  * Standard buffer head caching flags (uptodate, etc) are insufficient
  * in a clustered environment - a buffer may be marked up to date on
  * our local node but could have been modified by another cluster
  * member. As a result an additional (and performant) caching scheme
  * is required. A further requirement is that we consume as little
  * memory as possible - we never pin buffer_head structures in order
  * to cache them.
  *
  * We track the existence of up to date buffers on the inodes which
  * are associated with them. Because we don't want to pin
  * buffer_heads, this is only a (strong) hint and several other checks
  * are made in the I/O path to ensure that we don't use a stale or
  * invalid buffer without going to disk:
  *  - buffer_jbd is used liberally - if a bh is in the journal on
  *    this node then it *must* be up to date.
  *  - the standard buffer_uptodate() macro is used to detect buffers
  *    which may be invalid (even if we have an up to date tracking
  *    item for them)
  *
  * For a full understanding of how this code works together, one
  * should read the callers in dlmglue.c, the I/O functions in
  * buffer_head_io.c and ocfs2_journal_access in journal.c
  */
 
 #include <linux/fs.h>
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/highmem.h>
 #include <linux/buffer_head.h>
 #include <linux/rbtree.h>
 
 #include <cluster/masklog.h>
 
 #include "ocfs2.h"
 
 #include "inode.h"
 #include "uptodate.h"
 #include "ocfs2_trace.h"
 
 struct ocfs2_meta_cache_item {
     struct rb_node  c_node;
     sector_t    c_block;
 };
 
 static struct kmem_cache *ocfs2_uptodate_cachep;
 
 u64 ocfs2_metadata_cache_owner(struct ocfs2_caching_info *ci)
 {
     BUG_ON(!ci || !ci->ci_ops);
 
     return ci->ci_ops->co_owner(ci);
 }
 
 struct super_block *ocfs2_metadata_cache_get_super(struct ocfs2_caching_info *ci)
 {
     BUG_ON(!ci || !ci->ci_ops);
 
     return ci->ci_ops->co_get_super(ci);
 }
 
 static void ocfs2_metadata_cache_lock(struct ocfs2_caching_info *ci)
 {
     BUG_ON(!ci || !ci->ci_ops);
 
     ci->ci_ops->co_cache_lock(ci);
 }
 
 static void ocfs2_metadata_cache_unlock(struct ocfs2_caching_info *ci)
 {
     BUG_ON(!ci || !ci->ci_ops);
 
     ci->ci_ops->co_cache_unlock(ci);
 }
 
 void ocfs2_metadata_cache_io_lock(struct ocfs2_caching_info *ci)
 {
     BUG_ON(!ci || !ci->ci_ops);
 
     ci->ci_ops->co_io_lock(ci);
 }
 
 void ocfs2_metadata_cache_io_unlock(struct ocfs2_caching_info *ci)
 {
     BUG_ON(!ci || !ci->ci_ops);
 
     ci->ci_ops->co_io_unlock(ci);
 }
 
 
 static void ocfs2_metadata_cache_reset(struct ocfs2_caching_info *ci,
                        int clear)
 {
     ci->ci_flags |= OCFS2_CACHE_FL_INLINE;
     ci->ci_num_cached = 0;
 
     if (clear) {
         ci->ci_created_trans = 0;
         ci->ci_last_trans = 0;
     }
 }
 
 void ocfs2_metadata_cache_init(struct ocfs2_caching_info *ci,
                    const struct ocfs2_caching_operations *ops)
 {
     BUG_ON(!ops);
 
     ci->ci_ops = ops;
     ocfs2_metadata_cache_reset(ci, 1);
 }
 
 void ocfs2_metadata_cache_exit(struct ocfs2_caching_info *ci)
 {
     ocfs2_metadata_cache_purge(ci);
     ocfs2_metadata_cache_reset(ci, 1);
 }
 
 
 /* No lock taken here as 'root' is not expected to be visible to other
  * processes. */
 static unsigned int ocfs2_purge_copied_metadata_tree(struct rb_root *root)
 {
     unsigned int purged = 0;
     struct rb_node *node;
     struct ocfs2_meta_cache_item *item;
 
     while ((node = rb_last(root)) != NULL) {
         item = rb_entry(node, struct ocfs2_meta_cache_item, c_node);
 
         trace_ocfs2_purge_copied_metadata_tree(
                     (unsigned long long) item->c_block);
 
         rb_erase(&item->c_node, root);
         kmem_cache_free(ocfs2_uptodate_cachep, item);
 
         purged++;
     }
     return purged;
 }
 
 /* Called from locking and called from ocfs2_clear_inode. Dump the
  * cache for a given inode.
  *
  * This function is a few more lines longer than necessary due to some
  * accounting done here, but I think it's worth tracking down those
  * bugs sooner -- Mark */
 void ocfs2_metadata_cache_purge(struct ocfs2_caching_info *ci)
 {
     unsigned int tree, to_purge, purged;
     struct rb_root root = RB_ROOT;
 
     BUG_ON(!ci || !ci->ci_ops);
 
     ocfs2_metadata_cache_lock(ci);
     tree = !(ci->ci_flags & OCFS2_CACHE_FL_INLINE);
     to_purge = ci->ci_num_cached;
 
     trace_ocfs2_metadata_cache_purge(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         to_purge, tree);
 
     /* If we're a tree, save off the root so that we can safely
      * initialize the cache. We do the work to free tree members
      * without the spinlock. */
     if (tree)
         root = ci->ci_cache.ci_tree;
 
     ocfs2_metadata_cache_reset(ci, 0);
     ocfs2_metadata_cache_unlock(ci);
 
     purged = ocfs2_purge_copied_metadata_tree(&root);
     /* If possible, track the number wiped so that we can more
      * easily detect counting errors. Unfortunately, this is only
      * meaningful for trees. */
     if (tree && purged != to_purge)
         mlog(ML_ERROR, "Owner %llu, count = %u, purged = %u\n",
              (unsigned long long)ocfs2_metadata_cache_owner(ci),
              to_purge, purged);
 }
 
 /* Returns the index in the cache array, -1 if not found.
  * Requires ip_lock. */
 static int ocfs2_search_cache_array(struct ocfs2_caching_info *ci,
                     sector_t item)
 {
     int i;
 
     for (i = 0; i < ci->ci_num_cached; i++) {
         if (item == ci->ci_cache.ci_array[i])
             return i;
     }
 
     return -1;
 }
 
 /* Returns the cache item if found, otherwise NULL.
  * Requires ip_lock. */
 static struct ocfs2_meta_cache_item *
 ocfs2_search_cache_tree(struct ocfs2_caching_info *ci,
             sector_t block)
 {
     struct rb_node * n = ci->ci_cache.ci_tree.rb_node;
     struct ocfs2_meta_cache_item *item = NULL;
 
     while (n) {
         item = rb_entry(n, struct ocfs2_meta_cache_item, c_node);
 
         if (block < item->c_block)
             n = n->rb_left;
         else if (block > item->c_block)
             n = n->rb_right;
         else
             return item;
     }
 
     return NULL;
 }
 
 static int ocfs2_buffer_cached(struct ocfs2_caching_info *ci,
                    struct buffer_head *bh)
 {
     int index = -1;
     struct ocfs2_meta_cache_item *item = NULL;
 
     ocfs2_metadata_cache_lock(ci);
 
     trace_ocfs2_buffer_cached_begin(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long) bh->b_blocknr,
         !!(ci->ci_flags & OCFS2_CACHE_FL_INLINE));
 
     if (ci->ci_flags & OCFS2_CACHE_FL_INLINE)
         index = ocfs2_search_cache_array(ci, bh->b_blocknr);
     else
         item = ocfs2_search_cache_tree(ci, bh->b_blocknr);
 
     ocfs2_metadata_cache_unlock(ci);
 
     trace_ocfs2_buffer_cached_end(index, item);
 
     return (index != -1) || (item != NULL);
 }
 
 /* Warning: even if it returns true, this does *not* guarantee that
  * the block is stored in our inode metadata cache.
  *
  * This can be called under lock_buffer()
  */
 int ocfs2_buffer_uptodate(struct ocfs2_caching_info *ci,
               struct buffer_head *bh)
 {
     /* Doesn't matter if the bh is in our cache or not -- if it's
      * not marked uptodate then we know it can't have correct
      * data. */
     if (!buffer_uptodate(bh))
         return 0;
 
     /* OCFS2 does not allow multiple nodes to be changing the same
      * block at the same time. */
     if (buffer_jbd(bh))
         return 1;
 
     /* Ok, locally the buffer is marked as up to date, now search
      * our cache to see if we can trust that. */
     return ocfs2_buffer_cached(ci, bh);
 }
 
 /*
  * Determine whether a buffer is currently out on a read-ahead request.
  * ci_io_sem should be held to serialize submitters with the logic here.
  */
 int ocfs2_buffer_read_ahead(struct ocfs2_caching_info *ci,
                 struct buffer_head *bh)
 {
     return buffer_locked(bh) && ocfs2_buffer_cached(ci, bh);
 }
 
 /* Requires ip_lock */
 static void ocfs2_append_cache_array(struct ocfs2_caching_info *ci,
                      sector_t block)
 {
     BUG_ON(ci->ci_num_cached >= OCFS2_CACHE_INFO_MAX_ARRAY);
 
     trace_ocfs2_append_cache_array(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long)block, ci->ci_num_cached);
 
     ci->ci_cache.ci_array[ci->ci_num_cached] = block;
     ci->ci_num_cached++;
 }
 
 /* By now the caller should have checked that the item does *not*
  * exist in the tree.
  * Requires ip_lock. */
 static void __ocfs2_insert_cache_tree(struct ocfs2_caching_info *ci,
                       struct ocfs2_meta_cache_item *new)
 {
     sector_t block = new->c_block;
     struct rb_node *parent = NULL;
     struct rb_node **p = &ci->ci_cache.ci_tree.rb_node;
     struct ocfs2_meta_cache_item *tmp;
 
     trace_ocfs2_insert_cache_tree(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long)block, ci->ci_num_cached);
 
     while(*p) {
         parent = *p;
 
         tmp = rb_entry(parent, struct ocfs2_meta_cache_item, c_node);
 
         if (block < tmp->c_block)
             p = &(*p)->rb_left;
         else if (block > tmp->c_block)
             p = &(*p)->rb_right;
         else {
             /* This should never happen! */
             mlog(ML_ERROR, "Duplicate block %llu cached!\n",
                  (unsigned long long) block);
             BUG();
         }
     }
 
     rb_link_node(&new->c_node, parent, p);
     rb_insert_color(&new->c_node, &ci->ci_cache.ci_tree);
     ci->ci_num_cached++;
 }
 
 /* co_cache_lock() must be held */
 static inline int ocfs2_insert_can_use_array(struct ocfs2_caching_info *ci)
 {
     return (ci->ci_flags & OCFS2_CACHE_FL_INLINE) &&
         (ci->ci_num_cached < OCFS2_CACHE_INFO_MAX_ARRAY);
 }
 
 /* tree should be exactly OCFS2_CACHE_INFO_MAX_ARRAY wide. NULL the
  * pointers in tree after we use them - this allows caller to detect
  * when to free in case of error.
  *
  * The co_cache_lock() must be held. */
 static void ocfs2_expand_cache(struct ocfs2_caching_info *ci,
                    struct ocfs2_meta_cache_item **tree)
 {
     int i;
 
     mlog_bug_on_msg(ci->ci_num_cached != OCFS2_CACHE_INFO_MAX_ARRAY,
             "Owner %llu, num cached = %u, should be %u\n",
             (unsigned long long)ocfs2_metadata_cache_owner(ci),
             ci->ci_num_cached, OCFS2_CACHE_INFO_MAX_ARRAY);
     mlog_bug_on_msg(!(ci->ci_flags & OCFS2_CACHE_FL_INLINE),
             "Owner %llu not marked as inline anymore!\n",
             (unsigned long long)ocfs2_metadata_cache_owner(ci));
 
     /* Be careful to initialize the tree members *first* because
      * once the ci_tree is used, the array is junk... */
     for (i = 0; i < OCFS2_CACHE_INFO_MAX_ARRAY; i++)
         tree[i]->c_block = ci->ci_cache.ci_array[i];
 
     ci->ci_flags &= ~OCFS2_CACHE_FL_INLINE;
     ci->ci_cache.ci_tree = RB_ROOT;
     /* this will be set again by __ocfs2_insert_cache_tree */
     ci->ci_num_cached = 0;
 
     for (i = 0; i < OCFS2_CACHE_INFO_MAX_ARRAY; i++) {
         __ocfs2_insert_cache_tree(ci, tree[i]);
         tree[i] = NULL;
     }
 
     trace_ocfs2_expand_cache(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         ci->ci_flags, ci->ci_num_cached);
 }
 
 /* Slow path function - memory allocation is necessary. See the
  * comment above ocfs2_set_buffer_uptodate for more information. */
 static void __ocfs2_set_buffer_uptodate(struct ocfs2_caching_info *ci,
                     sector_t block,
                     int expand_tree)
 {
     int i;
     struct ocfs2_meta_cache_item *new = NULL;
     struct ocfs2_meta_cache_item *tree[OCFS2_CACHE_INFO_MAX_ARRAY] =
         { NULL, };
 
     trace_ocfs2_set_buffer_uptodate(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long)block, expand_tree);
 
     new = kmem_cache_alloc(ocfs2_uptodate_cachep, GFP_NOFS);
     if (!new) {
         mlog_errno(-ENOMEM);
         return;
     }
     new->c_block = block;
 
     if (expand_tree) {
         /* Do *not* allocate an array here - the removal code
          * has no way of tracking that. */
         for (i = 0; i < OCFS2_CACHE_INFO_MAX_ARRAY; i++) {
             tree[i] = kmem_cache_alloc(ocfs2_uptodate_cachep,
                            GFP_NOFS);
             if (!tree[i]) {
                 mlog_errno(-ENOMEM);
                 goto out_free;
             }
 
             /* These are initialized in ocfs2_expand_cache! */
         }
     }
 
     ocfs2_metadata_cache_lock(ci);
     if (ocfs2_insert_can_use_array(ci)) {
         /* Ok, items were removed from the cache in between
          * locks. Detect this and revert back to the fast path */
         ocfs2_append_cache_array(ci, block);
         ocfs2_metadata_cache_unlock(ci);
         goto out_free;
     }
 
     if (expand_tree)
         ocfs2_expand_cache(ci, tree);
 
     __ocfs2_insert_cache_tree(ci, new);
     ocfs2_metadata_cache_unlock(ci);
 
     new = NULL;
 out_free:
     if (new)
         kmem_cache_free(ocfs2_uptodate_cachep, new);
 
     /* If these were used, then ocfs2_expand_cache re-set them to
      * NULL for us. */
     if (tree[0]) {
         for (i = 0; i < OCFS2_CACHE_INFO_MAX_ARRAY; i++)
             if (tree[i])
                 kmem_cache_free(ocfs2_uptodate_cachep,
                         tree[i]);
     }
 }
 
 /* Item insertion is guarded by co_io_lock(), so the insertion path takes
  * advantage of this by not rechecking for a duplicate insert during
  * the slow case. Additionally, if the cache needs to be bumped up to
  * a tree, the code will not recheck after acquiring the lock --
  * multiple paths cannot be expanding to a tree at the same time.
  *
  * The slow path takes into account that items can be removed
  * (including the whole tree wiped and reset) when this process it out
  * allocating memory. In those cases, it reverts back to the fast
  * path.
  *
  * Note that this function may actually fail to insert the block if
  * memory cannot be allocated. This is not fatal however (but may
  * result in a performance penalty)
  *
  * Readahead buffers can be passed in here before the I/O request is
  * completed.
  */
 void ocfs2_set_buffer_uptodate(struct ocfs2_caching_info *ci,
                    struct buffer_head *bh)
 {
     int expand;
 
     /* The block may very well exist in our cache already, so avoid
      * doing any more work in that case. */
     if (ocfs2_buffer_cached(ci, bh))
         return;
 
     trace_ocfs2_set_buffer_uptodate_begin(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long)bh->b_blocknr);
 
     /* No need to recheck under spinlock - insertion is guarded by
      * co_io_lock() */
     ocfs2_metadata_cache_lock(ci);
     if (ocfs2_insert_can_use_array(ci)) {
         /* Fast case - it's an array and there's a free
          * spot. */
         ocfs2_append_cache_array(ci, bh->b_blocknr);
         ocfs2_metadata_cache_unlock(ci);
         return;
     }
 
     expand = 0;
     if (ci->ci_flags & OCFS2_CACHE_FL_INLINE) {
         /* We need to bump things up to a tree. */
         expand = 1;
     }
     ocfs2_metadata_cache_unlock(ci);
 
     __ocfs2_set_buffer_uptodate(ci, bh->b_blocknr, expand);
 }
 
 /* Called against a newly allocated buffer. Most likely nobody should
  * be able to read this sort of metadata while it's still being
  * allocated, but this is careful to take co_io_lock() anyway. */
 void ocfs2_set_new_buffer_uptodate(struct ocfs2_caching_info *ci,
                    struct buffer_head *bh)
 {
     /* This should definitely *not* exist in our cache */
     BUG_ON(ocfs2_buffer_cached(ci, bh));
 
     set_buffer_uptodate(bh);
 
     ocfs2_metadata_cache_io_lock(ci);
     ocfs2_set_buffer_uptodate(ci, bh);
     ocfs2_metadata_cache_io_unlock(ci);
 }
 
 /* Requires ip_lock. */
 static void ocfs2_remove_metadata_array(struct ocfs2_caching_info *ci,
                     int index)
 {
     sector_t *array = ci->ci_cache.ci_array;
     int bytes;
 
     BUG_ON(index < 0 || index >= OCFS2_CACHE_INFO_MAX_ARRAY);
     BUG_ON(index >= ci->ci_num_cached);
     BUG_ON(!ci->ci_num_cached);
 
     trace_ocfs2_remove_metadata_array(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         index, ci->ci_num_cached);
 
     ci->ci_num_cached--;
 
     /* don't need to copy if the array is now empty, or if we
      * removed at the tail */
     if (ci->ci_num_cached && index < ci->ci_num_cached) {
         bytes = sizeof(sector_t) * (ci->ci_num_cached - index);
         memmove(&array[index], &array[index + 1], bytes);
     }
 }
 
 /* Requires ip_lock. */
 static void ocfs2_remove_metadata_tree(struct ocfs2_caching_info *ci,
                        struct ocfs2_meta_cache_item *item)
 {
     trace_ocfs2_remove_metadata_tree(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long)item->c_block);
 
     rb_erase(&item->c_node, &ci->ci_cache.ci_tree);
     ci->ci_num_cached--;
 }
 
 static void ocfs2_remove_block_from_cache(struct ocfs2_caching_info *ci,
                       sector_t block)
 {
     int index;
     struct ocfs2_meta_cache_item *item = NULL;
 
     ocfs2_metadata_cache_lock(ci);
     trace_ocfs2_remove_block_from_cache(
         (unsigned long long)ocfs2_metadata_cache_owner(ci),
         (unsigned long long) block, ci->ci_num_cached,
         ci->ci_flags);
 
     if (ci->ci_flags & OCFS2_CACHE_FL_INLINE) {
         index = ocfs2_search_cache_array(ci, block);
         if (index != -1)
             ocfs2_remove_metadata_array(ci, index);
     } else {
         item = ocfs2_search_cache_tree(ci, block);
         if (item)
             ocfs2_remove_metadata_tree(ci, item);
     }
     ocfs2_metadata_cache_unlock(ci);
 
     if (item)
         kmem_cache_free(ocfs2_uptodate_cachep, item);
 }
 
 /*
  * Called when we remove a chunk of metadata from an inode. We don't
  * bother reverting things to an inlined array in the case of a remove
  * which moves us back under the limit.
  */
 void ocfs2_remove_from_cache(struct ocfs2_caching_info *ci,
                  struct buffer_head *bh)
 {
     sector_t block = bh->b_blocknr;
 
     ocfs2_remove_block_from_cache(ci, block);
 }
 
 /* Called when we remove xattr clusters from an inode. */
 void ocfs2_remove_xattr_clusters_from_cache(struct ocfs2_caching_info *ci,
                         sector_t block,
                         u32 c_len)
 {
     struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
     unsigned int i, b_len = ocfs2_clusters_to_blocks(sb, 1) * c_len;
 
     for (i = 0; i < b_len; i++, block++)
         ocfs2_remove_block_from_cache(ci, block);
 }
 
 int __init init_ocfs2_uptodate_cache(void)
 {
     ocfs2_uptodate_cachep = kmem_cache_create("ocfs2_uptodate",
                   sizeof(struct ocfs2_meta_cache_item),
                   0, SLAB_HWCACHE_ALIGN, NULL);
     if (!ocfs2_uptodate_cachep)
         return -ENOMEM;
 
     return 0;
 }
 
 void exit_ocfs2_uptodate_cache(void)
 {
     kmem_cache_destroy(ocfs2_uptodate_cachep);
 }

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