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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-only
 /*
  * linux/fs/nfs/write.c
  *
  * Write file data over NFS.
  *
  * Copyright (C) 1996, 1997, Olaf Kirch <okir@monad.swb.de>
  */
 
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/file.h>
 #include <linux/writeback.h>
 #include <linux/swap.h>
 #include <linux/migrate.h>
 
 #include <linux/sunrpc/clnt.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_mount.h>
 #include <linux/nfs_page.h>
 #include <linux/backing-dev.h>
 #include <linux/export.h>
 #include <linux/freezer.h>
 #include <linux/wait.h>
 #include <linux/iversion.h>
 
 #include <linux/uaccess.h>
 #include <linux/sched/mm.h>
 
 #include "delegation.h"
 #include "internal.h"
 #include "iostat.h"
 #include "nfs4_fs.h"
 #include "fscache.h"
 #include "pnfs.h"
 
 #include "nfstrace.h"
 
 #define NFSDBG_FACILITY     NFSDBG_PAGECACHE
 
 #define MIN_POOL_WRITE      (32)
 #define MIN_POOL_COMMIT     (4)
 
 struct nfs_io_completion {
     void (*complete)(void *data);
     void *data;
     struct kref refcount;
 };
 
 /*
  * Local function declarations
  */
 static void nfs_redirty_request(struct nfs_page *req);
 static const struct rpc_call_ops nfs_commit_ops;
 static const struct nfs_pgio_completion_ops nfs_async_write_completion_ops;
 static const struct nfs_commit_completion_ops nfs_commit_completion_ops;
 static const struct nfs_rw_ops nfs_rw_write_ops;
 static void nfs_inode_remove_request(struct nfs_page *req);
 static void nfs_clear_request_commit(struct nfs_page *req);
 static void nfs_init_cinfo_from_inode(struct nfs_commit_info *cinfo,
                       struct inode *inode);
 static struct nfs_page *
 nfs_page_search_commits_for_head_request_locked(struct nfs_inode *nfsi,
                         struct page *page);
 
 static struct kmem_cache *nfs_wdata_cachep;
 static mempool_t *nfs_wdata_mempool;
 static struct kmem_cache *nfs_cdata_cachep;
 static mempool_t *nfs_commit_mempool;
 
 struct nfs_commit_data *nfs_commitdata_alloc(void)
 {
     struct nfs_commit_data *p;
 
     p = kmem_cache_zalloc(nfs_cdata_cachep, nfs_io_gfp_mask());
     if (!p) {
         p = mempool_alloc(nfs_commit_mempool, GFP_NOWAIT);
         if (!p)
             return NULL;
         memset(p, 0, sizeof(*p));
     }
     INIT_LIST_HEAD(&p->pages);
     return p;
 }
 EXPORT_SYMBOL_GPL(nfs_commitdata_alloc);
 
 void nfs_commit_free(struct nfs_commit_data *p)
 {
     mempool_free(p, nfs_commit_mempool);
 }
 EXPORT_SYMBOL_GPL(nfs_commit_free);
 
 static struct nfs_pgio_header *nfs_writehdr_alloc(void)
 {
     struct nfs_pgio_header *p;
 
     p = kmem_cache_zalloc(nfs_wdata_cachep, nfs_io_gfp_mask());
     if (!p) {
         p = mempool_alloc(nfs_wdata_mempool, GFP_NOWAIT);
         if (!p)
             return NULL;
         memset(p, 0, sizeof(*p));
     }
     p->rw_mode = FMODE_WRITE;
     return p;
 }
 
 static void nfs_writehdr_free(struct nfs_pgio_header *hdr)
 {
     mempool_free(hdr, nfs_wdata_mempool);
 }
 
 static struct nfs_io_completion *nfs_io_completion_alloc(gfp_t gfp_flags)
 {
     return kmalloc(sizeof(struct nfs_io_completion), gfp_flags);
 }
 
 static void nfs_io_completion_init(struct nfs_io_completion *ioc,
         void (*complete)(void *), void *data)
 {
     ioc->complete = complete;
     ioc->data = data;
     kref_init(&ioc->refcount);
 }
 
 static void nfs_io_completion_release(struct kref *kref)
 {
     struct nfs_io_completion *ioc = container_of(kref,
             struct nfs_io_completion, refcount);
     ioc->complete(ioc->data);
     kfree(ioc);
 }
 
 static void nfs_io_completion_get(struct nfs_io_completion *ioc)
 {
     if (ioc != NULL)
         kref_get(&ioc->refcount);
 }
 
 static void nfs_io_completion_put(struct nfs_io_completion *ioc)
 {
     if (ioc != NULL)
         kref_put(&ioc->refcount, nfs_io_completion_release);
 }
 
 static void
 nfs_page_set_inode_ref(struct nfs_page *req, struct inode *inode)
 {
     if (!test_and_set_bit(PG_INODE_REF, &req->wb_flags)) {
         kref_get(&req->wb_kref);
         atomic_long_inc(&NFS_I(inode)->nrequests);
     }
 }
 
 static int
 nfs_cancel_remove_inode(struct nfs_page *req, struct inode *inode)
 {
     int ret;
 
     if (!test_bit(PG_REMOVE, &req->wb_flags))
         return 0;
     ret = nfs_page_group_lock(req);
     if (ret)
         return ret;
     if (test_and_clear_bit(PG_REMOVE, &req->wb_flags))
         nfs_page_set_inode_ref(req, inode);
     nfs_page_group_unlock(req);
     return 0;
 }
 
 static struct nfs_page *
 nfs_page_private_request(struct page *page)
 {
     if (!PagePrivate(page))
         return NULL;
     return (struct nfs_page *)page_private(page);
 }
 
 /*
  * nfs_page_find_head_request_locked - find head request associated with @page
  *
  * must be called while holding the inode lock.
  *
  * returns matching head request with reference held, or NULL if not found.
  */
 static struct nfs_page *
 nfs_page_find_private_request(struct page *page)
 {
     struct address_space *mapping = page_file_mapping(page);
     struct nfs_page *req;
 
     if (!PagePrivate(page))
         return NULL;
     spin_lock(&mapping->private_lock);
     req = nfs_page_private_request(page);
     if (req) {
         WARN_ON_ONCE(req->wb_head != req);
         kref_get(&req->wb_kref);
     }
     spin_unlock(&mapping->private_lock);
     return req;
 }
 
 static struct nfs_page *
 nfs_page_find_swap_request(struct page *page)
 {
     struct inode *inode = page_file_mapping(page)->host;
     struct nfs_inode *nfsi = NFS_I(inode);
     struct nfs_page *req = NULL;
     if (!PageSwapCache(page))
         return NULL;
     mutex_lock(&nfsi->commit_mutex);
     if (PageSwapCache(page)) {
         req = nfs_page_search_commits_for_head_request_locked(nfsi,
             page);
         if (req) {
             WARN_ON_ONCE(req->wb_head != req);
             kref_get(&req->wb_kref);
         }
     }
     mutex_unlock(&nfsi->commit_mutex);
     return req;
 }
 
 /*
  * nfs_page_find_head_request - find head request associated with @page
  *
  * returns matching head request with reference held, or NULL if not found.
  */
 static struct nfs_page *nfs_page_find_head_request(struct page *page)
 {
     struct nfs_page *req;
 
     req = nfs_page_find_private_request(page);
     if (!req)
         req = nfs_page_find_swap_request(page);
     return req;
 }
 
 static struct nfs_page *nfs_find_and_lock_page_request(struct page *page)
 {
     struct inode *inode = page_file_mapping(page)->host;
     struct nfs_page *req, *head;
     int ret;
 
     for (;;) {
         req = nfs_page_find_head_request(page);
         if (!req)
             return req;
         head = nfs_page_group_lock_head(req);
         if (head != req)
             nfs_release_request(req);
         if (IS_ERR(head))
             return head;
         ret = nfs_cancel_remove_inode(head, inode);
         if (ret < 0) {
             nfs_unlock_and_release_request(head);
             return ERR_PTR(ret);
         }
         /* Ensure that nobody removed the request before we locked it */
         if (head == nfs_page_private_request(page))
             break;
         if (PageSwapCache(page))
             break;
         nfs_unlock_and_release_request(head);
     }
     return head;
 }
 
 /* Adjust the file length if we're writing beyond the end */
 static void nfs_grow_file(struct page *page, unsigned int offset, unsigned int count)
 {
     struct inode *inode = page_file_mapping(page)->host;
     loff_t end, i_size;
     pgoff_t end_index;
 
     spin_lock(&inode->i_lock);
     i_size = i_size_read(inode);
     end_index = (i_size - 1) >> PAGE_SHIFT;
     if (i_size > 0 && page_index(page) < end_index)
         goto out;
     end = page_file_offset(page) + ((loff_t)offset+count);
     if (i_size >= end)
         goto out;
     trace_nfs_size_grow(inode, end);
     i_size_write(inode, end);
     NFS_I(inode)->cache_validity &= ~NFS_INO_INVALID_SIZE;
     nfs_inc_stats(inode, NFSIOS_EXTENDWRITE);
 out:
     spin_unlock(&inode->i_lock);
     nfs_fscache_invalidate(inode, 0);
 }
 
 /* A writeback failed: mark the page as bad, and invalidate the page cache */
 static void nfs_set_pageerror(struct address_space *mapping)
 {
     struct inode *inode = mapping->host;
 
     nfs_zap_mapping(mapping->host, mapping);
     /* Force file size revalidation */
     spin_lock(&inode->i_lock);
     nfs_set_cache_invalid(inode, NFS_INO_REVAL_FORCED |
                          NFS_INO_INVALID_CHANGE |
                          NFS_INO_INVALID_SIZE);
     spin_unlock(&inode->i_lock);
 }
 
 static void nfs_mapping_set_error(struct page *page, int error)
 {
     struct address_space *mapping = page_file_mapping(page);
 
     SetPageError(page);
     filemap_set_wb_err(mapping, error);
     if (mapping->host)
         errseq_set(&mapping->host->i_sb->s_wb_err,
                error == -ENOSPC ? -ENOSPC : -EIO);
     nfs_set_pageerror(mapping);
 }
 
 /*
  * nfs_page_group_search_locked
  * @head - head request of page group
  * @page_offset - offset into page
  *
  * Search page group with head @head to find a request that contains the
  * page offset @page_offset.
  *
  * Returns a pointer to the first matching nfs request, or NULL if no
  * match is found.
  *
  * Must be called with the page group lock held
  */
 static struct nfs_page *
 nfs_page_group_search_locked(struct nfs_page *head, unsigned int page_offset)
 {
     struct nfs_page *req;
 
     req = head;
     do {
         if (page_offset >= req->wb_pgbase &&
             page_offset < (req->wb_pgbase + req->wb_bytes))
             return req;
 
         req = req->wb_this_page;
     } while (req != head);
 
     return NULL;
 }
 
 /*
  * nfs_page_group_covers_page
  * @head - head request of page group
  *
  * Return true if the page group with head @head covers the whole page,
  * returns false otherwise
  */
 static bool nfs_page_group_covers_page(struct nfs_page *req)
 {
     struct nfs_page *tmp;
     unsigned int pos = 0;
     unsigned int len = nfs_page_length(req->wb_page);
 
     nfs_page_group_lock(req);
 
     for (;;) {
         tmp = nfs_page_group_search_locked(req->wb_head, pos);
         if (!tmp)
             break;
         pos = tmp->wb_pgbase + tmp->wb_bytes;
     }
 
     nfs_page_group_unlock(req);
     return pos >= len;
 }
 
 /* We can set the PG_uptodate flag if we see that a write request
  * covers the full page.
  */
 static void nfs_mark_uptodate(struct nfs_page *req)
 {
     if (PageUptodate(req->wb_page))
         return;
     if (!nfs_page_group_covers_page(req))
         return;
     SetPageUptodate(req->wb_page);
 }
 
 static int wb_priority(struct writeback_control *wbc)
 {
     int ret = 0;
 
     if (wbc->sync_mode == WB_SYNC_ALL)
         ret = FLUSH_COND_STABLE;
     return ret;
 }
 
 /*
  * NFS congestion control
  */
 
 int nfs_congestion_kb;
 
 #define NFS_CONGESTION_ON_THRESH    (nfs_congestion_kb >> (PAGE_SHIFT-10))
 #define NFS_CONGESTION_OFF_THRESH   \
     (NFS_CONGESTION_ON_THRESH - (NFS_CONGESTION_ON_THRESH >> 2))
 
 static void nfs_set_page_writeback(struct page *page)
 {
     struct inode *inode = page_file_mapping(page)->host;
     struct nfs_server *nfss = NFS_SERVER(inode);
     int ret = test_set_page_writeback(page);
 
     WARN_ON_ONCE(ret != 0);
 
     if (atomic_long_inc_return(&nfss->writeback) >
             NFS_CONGESTION_ON_THRESH)
         nfss->write_congested = 1;
 }
 
 static void nfs_end_page_writeback(struct nfs_page *req)
 {
     struct inode *inode = page_file_mapping(req->wb_page)->host;
     struct nfs_server *nfss = NFS_SERVER(inode);
     bool is_done;
 
     is_done = nfs_page_group_sync_on_bit(req, PG_WB_END);
     nfs_unlock_request(req);
     if (!is_done)
         return;
 
     end_page_writeback(req->wb_page);
     if (atomic_long_dec_return(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)
         nfss->write_congested = 0;
 }
 
 /*
  * nfs_destroy_unlinked_subrequests - destroy recently unlinked subrequests
  *
  * @destroy_list - request list (using wb_this_page) terminated by @old_head
  * @old_head - the old head of the list
  *
  * All subrequests must be locked and removed from all lists, so at this point
  * they are only "active" in this function, and possibly in nfs_wait_on_request
  * with a reference held by some other context.
  */
 static void
 nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list,
                  struct nfs_page *old_head,
                  struct inode *inode)
 {
     while (destroy_list) {
         struct nfs_page *subreq = destroy_list;
 
         destroy_list = (subreq->wb_this_page == old_head) ?
                    NULL : subreq->wb_this_page;
 
         /* Note: lock subreq in order to change subreq->wb_head */
         nfs_page_set_headlock(subreq);
         WARN_ON_ONCE(old_head != subreq->wb_head);
 
         /* make sure old group is not used */
         subreq->wb_this_page = subreq;
         subreq->wb_head = subreq;
 
         clear_bit(PG_REMOVE, &subreq->wb_flags);
 
         /* Note: races with nfs_page_group_destroy() */
         if (!kref_read(&subreq->wb_kref)) {
             /* Check if we raced with nfs_page_group_destroy() */
             if (test_and_clear_bit(PG_TEARDOWN, &subreq->wb_flags)) {
                 nfs_page_clear_headlock(subreq);
                 nfs_free_request(subreq);
             } else
                 nfs_page_clear_headlock(subreq);
             continue;
         }
         nfs_page_clear_headlock(subreq);
 
         nfs_release_request(old_head);
 
         if (test_and_clear_bit(PG_INODE_REF, &subreq->wb_flags)) {
             nfs_release_request(subreq);
             atomic_long_dec(&NFS_I(inode)->nrequests);
         }
 
         /* subreq is now totally disconnected from page group or any
          * write / commit lists. last chance to wake any waiters */
         nfs_unlock_and_release_request(subreq);
     }
 }
 
 /*
  * nfs_join_page_group - destroy subrequests of the head req
  * @head: the page used to lookup the "page group" of nfs_page structures
  * @inode: Inode to which the request belongs.
  *
  * This function joins all sub requests to the head request by first
  * locking all requests in the group, cancelling any pending operations
  * and finally updating the head request to cover the whole range covered by
  * the (former) group.  All subrequests are removed from any write or commit
  * lists, unlinked from the group and destroyed.
  */
 void
 nfs_join_page_group(struct nfs_page *head, struct inode *inode)
 {
     struct nfs_page *subreq;
     struct nfs_page *destroy_list = NULL;
     unsigned int pgbase, off, bytes;
 
     pgbase = head->wb_pgbase;
     bytes = head->wb_bytes;
     off = head->wb_offset;
     for (subreq = head->wb_this_page; subreq != head;
             subreq = subreq->wb_this_page) {
         /* Subrequests should always form a contiguous range */
         if (pgbase > subreq->wb_pgbase) {
             off -= pgbase - subreq->wb_pgbase;
             bytes += pgbase - subreq->wb_pgbase;
             pgbase = subreq->wb_pgbase;
         }
         bytes = max(subreq->wb_pgbase + subreq->wb_bytes
                 - pgbase, bytes);
     }
 
     /* Set the head request's range to cover the former page group */
     head->wb_pgbase = pgbase;
     head->wb_bytes = bytes;
     head->wb_offset = off;
 
     /* Now that all requests are locked, make sure they aren't on any list.
      * Commit list removal accounting is done after locks are dropped */
     subreq = head;
     do {
         nfs_clear_request_commit(subreq);
         subreq = subreq->wb_this_page;
     } while (subreq != head);
 
     /* unlink subrequests from head, destroy them later */
     if (head->wb_this_page != head) {
         /* destroy list will be terminated by head */
         destroy_list = head->wb_this_page;
         head->wb_this_page = head;
     }
 
     nfs_destroy_unlinked_subrequests(destroy_list, head, inode);
 }
 
 /*
  * nfs_lock_and_join_requests - join all subreqs to the head req
  * @page: the page used to lookup the "page group" of nfs_page structures
  *
  * This function joins all sub requests to the head request by first
  * locking all requests in the group, cancelling any pending operations
  * and finally updating the head request to cover the whole range covered by
  * the (former) group.  All subrequests are removed from any write or commit
  * lists, unlinked from the group and destroyed.
  *
  * Returns a locked, referenced pointer to the head request - which after
  * this call is guaranteed to be the only request associated with the page.
  * Returns NULL if no requests are found for @page, or a ERR_PTR if an
  * error was encountered.
  */
 static struct nfs_page *
 nfs_lock_and_join_requests(struct page *page)
 {
     struct inode *inode = page_file_mapping(page)->host;
     struct nfs_page *head;
     int ret;
 
     /*
      * A reference is taken only on the head request which acts as a
      * reference to the whole page group - the group will not be destroyed
      * until the head reference is released.
      */
     head = nfs_find_and_lock_page_request(page);
     if (IS_ERR_OR_NULL(head))
         return head;
 
     /* lock each request in the page group */
     ret = nfs_page_group_lock_subrequests(head);
     if (ret < 0) {
         nfs_unlock_and_release_request(head);
         return ERR_PTR(ret);
     }
 
     nfs_join_page_group(head, inode);
 
     return head;
 }
 
 static void nfs_write_error(struct nfs_page *req, int error)
 {
     trace_nfs_write_error(page_file_mapping(req->wb_page)->host, req,
                   error);
     nfs_mapping_set_error(req->wb_page, error);
     nfs_inode_remove_request(req);
     nfs_end_page_writeback(req);
     nfs_release_request(req);
 }
 
 /*
  * Find an associated nfs write request, and prepare to flush it out
  * May return an error if the user signalled nfs_wait_on_request().
  */
 static int nfs_page_async_flush(struct page *page,
                 struct writeback_control *wbc,
                 struct nfs_pageio_descriptor *pgio)
 {
     struct nfs_page *req;
     int ret = 0;
 
     req = nfs_lock_and_join_requests(page);
     if (!req)
         goto out;
     ret = PTR_ERR(req);
     if (IS_ERR(req))
         goto out;
 
     nfs_set_page_writeback(page);
     WARN_ON_ONCE(test_bit(PG_CLEAN, &req->wb_flags));
 
     /* If there is a fatal error that covers this write, just exit */
     ret = pgio->pg_error;
     if (nfs_error_is_fatal_on_server(ret))
         goto out_launder;
 
     ret = 0;
     if (!nfs_pageio_add_request(pgio, req)) {
         ret = pgio->pg_error;
         /*
          * Remove the problematic req upon fatal errors on the server
          */
         if (nfs_error_is_fatal_on_server(ret))
             goto out_launder;
         if (wbc->sync_mode == WB_SYNC_NONE)
             ret = AOP_WRITEPAGE_ACTIVATE;
         redirty_page_for_writepage(wbc, page);
         nfs_redirty_request(req);
         pgio->pg_error = 0;
     } else
         nfs_add_stats(page_file_mapping(page)->host,
                 NFSIOS_WRITEPAGES, 1);
 out:
     return ret;
 out_launder:
     nfs_write_error(req, ret);
     return 0;
 }
 
 static int nfs_do_writepage(struct page *page, struct writeback_control *wbc,
                 struct nfs_pageio_descriptor *pgio)
 {
     nfs_pageio_cond_complete(pgio, page_index(page));
     return nfs_page_async_flush(page, wbc, pgio);
 }
 
 /*
  * Write an mmapped page to the server.
  */
 static int nfs_writepage_locked(struct page *page,
                 struct writeback_control *wbc)
 {
     struct nfs_pageio_descriptor pgio;
     struct inode *inode = page_file_mapping(page)->host;
     int err;
 
     if (wbc->sync_mode == WB_SYNC_NONE &&
         NFS_SERVER(inode)->write_congested)
         return AOP_WRITEPAGE_ACTIVATE;
 
     nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
     nfs_pageio_init_write(&pgio, inode, 0,
                 false, &nfs_async_write_completion_ops);
     err = nfs_do_writepage(page, wbc, &pgio);
     pgio.pg_error = 0;
     nfs_pageio_complete(&pgio);
     return err;
 }
 
 int nfs_writepage(struct page *page, struct writeback_control *wbc)
 {
     int ret;
 
     ret = nfs_writepage_locked(page, wbc);
     if (ret != AOP_WRITEPAGE_ACTIVATE)
         unlock_page(page);
     return ret;
 }
 
 static int nfs_writepages_callback(struct page *page, struct writeback_control *wbc, void *data)
 {
     int ret;
 
     ret = nfs_do_writepage(page, wbc, data);
     if (ret != AOP_WRITEPAGE_ACTIVATE)
         unlock_page(page);
     return ret;
 }
 
 static void nfs_io_completion_commit(void *inode)
 {
     nfs_commit_inode(inode, 0);
 }
 
 int nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
     struct inode *inode = mapping->host;
     struct nfs_pageio_descriptor pgio;
     struct nfs_io_completion *ioc = NULL;
     unsigned int mntflags = NFS_SERVER(inode)->flags;
     int priority = 0;
     int err;
 
     if (wbc->sync_mode == WB_SYNC_NONE &&
         NFS_SERVER(inode)->write_congested)
         return 0;
 
     nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGES);
 
     if (!(mntflags & NFS_MOUNT_WRITE_EAGER) || wbc->for_kupdate ||
         wbc->for_background || wbc->for_sync || wbc->for_reclaim) {
         ioc = nfs_io_completion_alloc(GFP_KERNEL);
         if (ioc)
             nfs_io_completion_init(ioc, nfs_io_completion_commit,
                            inode);
         priority = wb_priority(wbc);
     }
 
     do {
         nfs_pageio_init_write(&pgio, inode, priority, false,
                       &nfs_async_write_completion_ops);
         pgio.pg_io_completion = ioc;
         err = write_cache_pages(mapping, wbc, nfs_writepages_callback,
                     &pgio);
         pgio.pg_error = 0;
         nfs_pageio_complete(&pgio);
     } while (err < 0 && !nfs_error_is_fatal(err));
     nfs_io_completion_put(ioc);
 
     if (err < 0)
         goto out_err;
     return 0;
 out_err:
     return err;
 }
 
 /*
  * Insert a write request into an inode
  */
 static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
 {
     struct address_space *mapping = page_file_mapping(req->wb_page);
     struct nfs_inode *nfsi = NFS_I(inode);
 
     WARN_ON_ONCE(req->wb_this_page != req);
 
     /* Lock the request! */
     nfs_lock_request(req);
 
     /*
      * Swap-space should not get truncated. Hence no need to plug the race
      * with invalidate/truncate.
      */
     spin_lock(&mapping->private_lock);
     if (likely(!PageSwapCache(req->wb_page))) {
         set_bit(PG_MAPPED, &req->wb_flags);
         SetPagePrivate(req->wb_page);
         set_page_private(req->wb_page, (unsigned long)req);
     }
     spin_unlock(&mapping->private_lock);
     atomic_long_inc(&nfsi->nrequests);
     /* this a head request for a page group - mark it as having an
      * extra reference so sub groups can follow suit.
      * This flag also informs pgio layer when to bump nrequests when
      * adding subrequests. */
     WARN_ON(test_and_set_bit(PG_INODE_REF, &req->wb_flags));
     kref_get(&req->wb_kref);
 }
 
 /*
  * Remove a write request from an inode
  */
 static void nfs_inode_remove_request(struct nfs_page *req)
 {
     struct address_space *mapping = page_file_mapping(req->wb_page);
     struct inode *inode = mapping->host;
     struct nfs_inode *nfsi = NFS_I(inode);
     struct nfs_page *head;
 
     if (nfs_page_group_sync_on_bit(req, PG_REMOVE)) {
         head = req->wb_head;
 
         spin_lock(&mapping->private_lock);
         if (likely(head->wb_page && !PageSwapCache(head->wb_page))) {
             set_page_private(head->wb_page, 0);
             ClearPagePrivate(head->wb_page);
             clear_bit(PG_MAPPED, &head->wb_flags);
         }
         spin_unlock(&mapping->private_lock);
     }
 
     if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags)) {
         nfs_release_request(req);
         atomic_long_dec(&nfsi->nrequests);
     }
 }
 
 static void
 nfs_mark_request_dirty(struct nfs_page *req)
 {
     if (req->wb_page)
         __set_page_dirty_nobuffers(req->wb_page);
 }
 
 /*
  * nfs_page_search_commits_for_head_request_locked
  *
  * Search through commit lists on @inode for the head request for @page.
  * Must be called while holding the inode (which is cinfo) lock.
  *
  * Returns the head request if found, or NULL if not found.
  */
 static struct nfs_page *
 nfs_page_search_commits_for_head_request_locked(struct nfs_inode *nfsi,
                         struct page *page)
 {
     struct nfs_page *freq, *t;
     struct nfs_commit_info cinfo;
     struct inode *inode = &nfsi->vfs_inode;
 
     nfs_init_cinfo_from_inode(&cinfo, inode);
 
     /* search through pnfs commit lists */
     freq = pnfs_search_commit_reqs(inode, &cinfo, page);
     if (freq)
         return freq->wb_head;
 
     /* Linearly search the commit list for the correct request */
     list_for_each_entry_safe(freq, t, &cinfo.mds->list, wb_list) {
         if (freq->wb_page == page)
             return freq->wb_head;
     }
 
     return NULL;
 }
 
 /**
  * nfs_request_add_commit_list_locked - add request to a commit list
  * @req: pointer to a struct nfs_page
  * @dst: commit list head
  * @cinfo: holds list lock and accounting info
  *
  * This sets the PG_CLEAN bit, updates the cinfo count of
  * number of outstanding requests requiring a commit as well as
  * the MM page stats.
  *
  * The caller must hold NFS_I(cinfo->inode)->commit_mutex, and the
  * nfs_page lock.
  */
 void
 nfs_request_add_commit_list_locked(struct nfs_page *req, struct list_head *dst,
                 struct nfs_commit_info *cinfo)
 {
     set_bit(PG_CLEAN, &req->wb_flags);
     nfs_list_add_request(req, dst);
     atomic_long_inc(&cinfo->mds->ncommit);
 }
 EXPORT_SYMBOL_GPL(nfs_request_add_commit_list_locked);
 
 /**
  * nfs_request_add_commit_list - add request to a commit list
  * @req: pointer to a struct nfs_page
  * @cinfo: holds list lock and accounting info
  *
  * This sets the PG_CLEAN bit, updates the cinfo count of
  * number of outstanding requests requiring a commit as well as
  * the MM page stats.
  *
  * The caller must _not_ hold the cinfo->lock, but must be
  * holding the nfs_page lock.
  */
 void
 nfs_request_add_commit_list(struct nfs_page *req, struct nfs_commit_info *cinfo)
 {
     mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
     nfs_request_add_commit_list_locked(req, &cinfo->mds->list, cinfo);
     mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
     if (req->wb_page)
         nfs_mark_page_unstable(req->wb_page, cinfo);
 }
 EXPORT_SYMBOL_GPL(nfs_request_add_commit_list);
 
 /**
  * nfs_request_remove_commit_list - Remove request from a commit list
  * @req: pointer to a nfs_page
  * @cinfo: holds list lock and accounting info
  *
  * This clears the PG_CLEAN bit, and updates the cinfo's count of
  * number of outstanding requests requiring a commit
  * It does not update the MM page stats.
  *
  * The caller _must_ hold the cinfo->lock and the nfs_page lock.
  */
 void
 nfs_request_remove_commit_list(struct nfs_page *req,
                    struct nfs_commit_info *cinfo)
 {
     if (!test_and_clear_bit(PG_CLEAN, &(req)->wb_flags))
         return;
     nfs_list_remove_request(req);
     atomic_long_dec(&cinfo->mds->ncommit);
 }
 EXPORT_SYMBOL_GPL(nfs_request_remove_commit_list);
 
 static void nfs_init_cinfo_from_inode(struct nfs_commit_info *cinfo,
                       struct inode *inode)
 {
     cinfo->inode = inode;
     cinfo->mds = &NFS_I(inode)->commit_info;
     cinfo->ds = pnfs_get_ds_info(inode);
     cinfo->dreq = NULL;
     cinfo->completion_ops = &nfs_commit_completion_ops;
 }
 
 void nfs_init_cinfo(struct nfs_commit_info *cinfo,
             struct inode *inode,
             struct nfs_direct_req *dreq)
 {
     if (dreq)
         nfs_init_cinfo_from_dreq(cinfo, dreq);
     else
         nfs_init_cinfo_from_inode(cinfo, inode);
 }
 EXPORT_SYMBOL_GPL(nfs_init_cinfo);
 
 /*
  * Add a request to the inode's commit list.
  */
 void
 nfs_mark_request_commit(struct nfs_page *req, struct pnfs_layout_segment *lseg,
             struct nfs_commit_info *cinfo, u32 ds_commit_idx)
 {
     if (pnfs_mark_request_commit(req, lseg, cinfo, ds_commit_idx))
         return;
     nfs_request_add_commit_list(req, cinfo);
 }
 
 static void
 nfs_clear_page_commit(struct page *page)
 {
     dec_node_page_state(page, NR_WRITEBACK);
     dec_wb_stat(&inode_to_bdi(page_file_mapping(page)->host)->wb,
             WB_WRITEBACK);
 }
 
 /* Called holding the request lock on @req */
 static void
 nfs_clear_request_commit(struct nfs_page *req)
 {
     if (test_bit(PG_CLEAN, &req->wb_flags)) {
         struct nfs_open_context *ctx = nfs_req_openctx(req);
         struct inode *inode = d_inode(ctx->dentry);
         struct nfs_commit_info cinfo;
 
         nfs_init_cinfo_from_inode(&cinfo, inode);
         mutex_lock(&NFS_I(inode)->commit_mutex);
         if (!pnfs_clear_request_commit(req, &cinfo)) {
             nfs_request_remove_commit_list(req, &cinfo);
         }
         mutex_unlock(&NFS_I(inode)->commit_mutex);
         nfs_clear_page_commit(req->wb_page);
     }
 }
 
 int nfs_write_need_commit(struct nfs_pgio_header *hdr)
 {
     if (hdr->verf.committed == NFS_DATA_SYNC)
         return hdr->lseg == NULL;
     return hdr->verf.committed != NFS_FILE_SYNC;
 }
 
 static void nfs_async_write_init(struct nfs_pgio_header *hdr)
 {
     nfs_io_completion_get(hdr->io_completion);
 }
 
 static void nfs_write_completion(struct nfs_pgio_header *hdr)
 {
     struct nfs_commit_info cinfo;
     unsigned long bytes = 0;
 
     if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
         goto out;
     nfs_init_cinfo_from_inode(&cinfo, hdr->inode);
     while (!list_empty(&hdr->pages)) {
         struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 
         bytes += req->wb_bytes;
         nfs_list_remove_request(req);
         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) &&
             (hdr->good_bytes < bytes)) {
             trace_nfs_comp_error(hdr->inode, req, hdr->error);
             nfs_mapping_set_error(req->wb_page, hdr->error);
             goto remove_req;
         }
         if (nfs_write_need_commit(hdr)) {
             /* Reset wb_nio, since the write was successful. */
             req->wb_nio = 0;
             memcpy(&req->wb_verf, &hdr->verf.verifier, sizeof(req->wb_verf));
             nfs_mark_request_commit(req, hdr->lseg, &cinfo,
                 hdr->pgio_mirror_idx);
             goto next;
         }
 remove_req:
         nfs_inode_remove_request(req);
 next:
         nfs_end_page_writeback(req);
         nfs_release_request(req);
     }
 out:
     nfs_io_completion_put(hdr->io_completion);
     hdr->release(hdr);
 }
 
 unsigned long
 nfs_reqs_to_commit(struct nfs_commit_info *cinfo)
 {
     return atomic_long_read(&cinfo->mds->ncommit);
 }
 
 /* NFS_I(cinfo->inode)->commit_mutex held by caller */
 int
 nfs_scan_commit_list(struct list_head *src, struct list_head *dst,
              struct nfs_commit_info *cinfo, int max)
 {
     struct nfs_page *req, *tmp;
     int ret = 0;
 
     list_for_each_entry_safe(req, tmp, src, wb_list) {
         kref_get(&req->wb_kref);
         if (!nfs_lock_request(req)) {
             nfs_release_request(req);
             continue;
         }
         nfs_request_remove_commit_list(req, cinfo);
         clear_bit(PG_COMMIT_TO_DS, &req->wb_flags);
         nfs_list_add_request(req, dst);
         ret++;
         if ((ret == max) && !cinfo->dreq)
             break;
         cond_resched();
     }
     return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_scan_commit_list);
 
 /*
  * nfs_scan_commit - Scan an inode for commit requests
  * @inode: NFS inode to scan
  * @dst: mds destination list
  * @cinfo: mds and ds lists of reqs ready to commit
  *
  * Moves requests from the inode's 'commit' request list.
  * The requests are *not* checked to ensure that they form a contiguous set.
  */
 int
 nfs_scan_commit(struct inode *inode, struct list_head *dst,
         struct nfs_commit_info *cinfo)
 {
     int ret = 0;
 
     if (!atomic_long_read(&cinfo->mds->ncommit))
         return 0;
     mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
     if (atomic_long_read(&cinfo->mds->ncommit) > 0) {
         const int max = INT_MAX;
 
         ret = nfs_scan_commit_list(&cinfo->mds->list, dst,
                        cinfo, max);
         ret += pnfs_scan_commit_lists(inode, cinfo, max - ret);
     }
     mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
     return ret;
 }
 
 /*
  * Search for an existing write request, and attempt to update
  * it to reflect a new dirty region on a given page.
  *
  * If the attempt fails, then the existing request is flushed out
  * to disk.
  */
 static struct nfs_page *nfs_try_to_update_request(struct inode *inode,
         struct page *page,
         unsigned int offset,
         unsigned int bytes)
 {
     struct nfs_page *req;
     unsigned int rqend;
     unsigned int end;
     int error;
 
     end = offset + bytes;
 
     req = nfs_lock_and_join_requests(page);
     if (IS_ERR_OR_NULL(req))
         return req;
 
     rqend = req->wb_offset + req->wb_bytes;
     /*
      * Tell the caller to flush out the request if
      * the offsets are non-contiguous.
      * Note: nfs_flush_incompatible() will already
      * have flushed out requests having wrong owners.
      */
     if (offset > rqend || end < req->wb_offset)
         goto out_flushme;
 
     /* Okay, the request matches. Update the region */
     if (offset < req->wb_offset) {
         req->wb_offset = offset;
         req->wb_pgbase = offset;
     }
     if (end > rqend)
         req->wb_bytes = end - req->wb_offset;
     else
         req->wb_bytes = rqend - req->wb_offset;
     req->wb_nio = 0;
     return req;
 out_flushme:
     /*
      * Note: we mark the request dirty here because
      * nfs_lock_and_join_requests() cannot preserve
      * commit flags, so we have to replay the write.
      */
     nfs_mark_request_dirty(req);
     nfs_unlock_and_release_request(req);
     error = nfs_wb_page(inode, page);
     return (error < 0) ? ERR_PTR(error) : NULL;
 }
 
 /*
  * Try to update an existing write request, or create one if there is none.
  *
  * Note: Should always be called with the Page Lock held to prevent races
  * if we have to add a new request. Also assumes that the caller has
  * already called nfs_flush_incompatible() if necessary.
  */
 static struct nfs_page * nfs_setup_write_request(struct nfs_open_context* ctx,
         struct page *page, unsigned int offset, unsigned int bytes)
 {
     struct inode *inode = page_file_mapping(page)->host;
     struct nfs_page *req;
 
     req = nfs_try_to_update_request(inode, page, offset, bytes);
     if (req != NULL)
         goto out;
     req = nfs_create_request(ctx, page, offset, bytes);
     if (IS_ERR(req))
         goto out;
     nfs_inode_add_request(inode, req);
 out:
     return req;
 }
 
 static int nfs_writepage_setup(struct nfs_open_context *ctx, struct page *page,
         unsigned int offset, unsigned int count)
 {
     struct nfs_page *req;
 
     req = nfs_setup_write_request(ctx, page, offset, count);
     if (IS_ERR(req))
         return PTR_ERR(req);
     /* Update file length */
     nfs_grow_file(page, offset, count);
     nfs_mark_uptodate(req);
     nfs_mark_request_dirty(req);
     nfs_unlock_and_release_request(req);
     return 0;
 }
 
 int nfs_flush_incompatible(struct file *file, struct page *page)
 {
     struct nfs_open_context *ctx = nfs_file_open_context(file);
     struct nfs_lock_context *l_ctx;
     struct file_lock_context *flctx = file_inode(file)->i_flctx;
     struct nfs_page *req;
     int do_flush, status;
     /*
      * Look for a request corresponding to this page. If there
      * is one, and it belongs to another file, we flush it out
      * before we try to copy anything into the page. Do this
      * due to the lack of an ACCESS-type call in NFSv2.
      * Also do the same if we find a request from an existing
      * dropped page.
      */
     do {
         req = nfs_page_find_head_request(page);
         if (req == NULL)
             return 0;
         l_ctx = req->wb_lock_context;
         do_flush = req->wb_page != page ||
             !nfs_match_open_context(nfs_req_openctx(req), ctx);
         if (l_ctx && flctx &&
             !(list_empty_careful(&flctx->flc_posix) &&
               list_empty_careful(&flctx->flc_flock))) {
             do_flush |= l_ctx->lockowner != current->files;
         }
         nfs_release_request(req);
         if (!do_flush)
             return 0;
         status = nfs_wb_page(page_file_mapping(page)->host, page);
     } while (status == 0);
     return status;
 }
 
 /*
  * Avoid buffered writes when a open context credential's key would
  * expire soon.
  *
  * Returns -EACCES if the key will expire within RPC_KEY_EXPIRE_FAIL.
  *
  * Return 0 and set a credential flag which triggers the inode to flush
  * and performs  NFS_FILE_SYNC writes if the key will expired within
  * RPC_KEY_EXPIRE_TIMEO.
  */
 int
 nfs_key_timeout_notify(struct file *filp, struct inode *inode)
 {
     struct nfs_open_context *ctx = nfs_file_open_context(filp);
 
     if (nfs_ctx_key_to_expire(ctx, inode) &&
         !rcu_access_pointer(ctx->ll_cred))
         /* Already expired! */
         return -EACCES;
     return 0;
 }
 
 /*
  * Test if the open context credential key is marked to expire soon.
  */
 bool nfs_ctx_key_to_expire(struct nfs_open_context *ctx, struct inode *inode)
 {
     struct rpc_auth *auth = NFS_SERVER(inode)->client->cl_auth;
     struct rpc_cred *cred, *new, *old = NULL;
     struct auth_cred acred = {
         .cred = ctx->cred,
     };
     bool ret = false;
 
     rcu_read_lock();
     cred = rcu_dereference(ctx->ll_cred);
     if (cred && !(cred->cr_ops->crkey_timeout &&
               cred->cr_ops->crkey_timeout(cred)))
         goto out;
     rcu_read_unlock();
 
     new = auth->au_ops->lookup_cred(auth, &acred, 0);
     if (new == cred) {
         put_rpccred(new);
         return true;
     }
     if (IS_ERR_OR_NULL(new)) {
         new = NULL;
         ret = true;
     } else if (new->cr_ops->crkey_timeout &&
            new->cr_ops->crkey_timeout(new))
         ret = true;
 
     rcu_read_lock();
     old = rcu_dereference_protected(xchg(&ctx->ll_cred,
                          RCU_INITIALIZER(new)), 1);
 out:
     rcu_read_unlock();
     put_rpccred(old);
     return ret;
 }
 
 /*
  * If the page cache is marked as unsafe or invalid, then we can't rely on
  * the PageUptodate() flag. In this case, we will need to turn off
  * write optimisations that depend on the page contents being correct.
  */
 static bool nfs_write_pageuptodate(struct page *page, struct inode *inode,
                    unsigned int pagelen)
 {
     struct nfs_inode *nfsi = NFS_I(inode);
 
     if (nfs_have_delegated_attributes(inode))
         goto out;
     if (nfsi->cache_validity &
         (NFS_INO_INVALID_CHANGE | NFS_INO_INVALID_SIZE))
         return false;
     smp_rmb();
     if (test_bit(NFS_INO_INVALIDATING, &nfsi->flags) && pagelen != 0)
         return false;
 out:
     if (nfsi->cache_validity & NFS_INO_INVALID_DATA && pagelen != 0)
         return false;
     return PageUptodate(page) != 0;
 }
 
 static bool
 is_whole_file_wrlock(struct file_lock *fl)
 {
     return fl->fl_start == 0 && fl->fl_end == OFFSET_MAX &&
             fl->fl_type == F_WRLCK;
 }
 
 /* If we know the page is up to date, and we're not using byte range locks (or
  * if we have the whole file locked for writing), it may be more efficient to
  * extend the write to cover the entire page in order to avoid fragmentation
  * inefficiencies.
  *
  * If the file is opened for synchronous writes then we can just skip the rest
  * of the checks.
  */
 static int nfs_can_extend_write(struct file *file, struct page *page,
                 struct inode *inode, unsigned int pagelen)
 {
     int ret;
     struct file_lock_context *flctx = inode->i_flctx;
     struct file_lock *fl;
 
     if (file->f_flags & O_DSYNC)
         return 0;
     if (!nfs_write_pageuptodate(page, inode, pagelen))
         return 0;
     if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
         return 1;
     if (!flctx || (list_empty_careful(&flctx->flc_flock) &&
                list_empty_careful(&flctx->flc_posix)))
         return 1;
 
     /* Check to see if there are whole file write locks */
     ret = 0;
     spin_lock(&flctx->flc_lock);
     if (!list_empty(&flctx->flc_posix)) {
         fl = list_first_entry(&flctx->flc_posix, struct file_lock,
                     fl_list);
         if (is_whole_file_wrlock(fl))
             ret = 1;
     } else if (!list_empty(&flctx->flc_flock)) {
         fl = list_first_entry(&flctx->flc_flock, struct file_lock,
                     fl_list);
         if (fl->fl_type == F_WRLCK)
             ret = 1;
     }
     spin_unlock(&flctx->flc_lock);
     return ret;
 }
 
 /*
  * Update and possibly write a cached page of an NFS file.
  *
  * XXX: Keep an eye on generic_file_read to make sure it doesn't do bad
  * things with a page scheduled for an RPC call (e.g. invalidate it).
  */
 int nfs_updatepage(struct file *file, struct page *page,
         unsigned int offset, unsigned int count)
 {
     struct nfs_open_context *ctx = nfs_file_open_context(file);
     struct address_space *mapping = page_file_mapping(page);
     struct inode    *inode = mapping->host;
     unsigned int    pagelen = nfs_page_length(page);
     int     status = 0;
 
     nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);
 
     dprintk("NFS:       nfs_updatepage(%pD2 %d@%lld)\n",
         file, count, (long long)(page_file_offset(page) + offset));
 
     if (!count)
         goto out;
 
     if (nfs_can_extend_write(file, page, inode, pagelen)) {
         count = max(count + offset, pagelen);
         offset = 0;
     }
 
     status = nfs_writepage_setup(ctx, page, offset, count);
     if (status < 0)
         nfs_set_pageerror(mapping);
 out:
     dprintk("NFS:       nfs_updatepage returns %d (isize %lld)\n",
             status, (long long)i_size_read(inode));
     return status;
 }
 
 static int flush_task_priority(int how)
 {
     switch (how & (FLUSH_HIGHPRI|FLUSH_LOWPRI)) {
         case FLUSH_HIGHPRI:
             return RPC_PRIORITY_HIGH;
         case FLUSH_LOWPRI:
             return RPC_PRIORITY_LOW;
     }
     return RPC_PRIORITY_NORMAL;
 }
 
 static void nfs_initiate_write(struct nfs_pgio_header *hdr,
                    struct rpc_message *msg,
                    const struct nfs_rpc_ops *rpc_ops,
                    struct rpc_task_setup *task_setup_data, int how)
 {
     int priority = flush_task_priority(how);
 
     if (IS_SWAPFILE(hdr->inode))
         task_setup_data->flags |= RPC_TASK_SWAPPER;
     task_setup_data->priority = priority;
     rpc_ops->write_setup(hdr, msg, &task_setup_data->rpc_client);
     trace_nfs_initiate_write(hdr);
 }
 
 /* If a nfs_flush_* function fails, it should remove reqs from @head and
  * call this on each, which will prepare them to be retried on next
  * writeback using standard nfs.
  */
 static void nfs_redirty_request(struct nfs_page *req)
 {
     struct nfs_inode *nfsi = NFS_I(page_file_mapping(req->wb_page)->host);
 
     /* Bump the transmission count */
     req->wb_nio++;
     nfs_mark_request_dirty(req);
     atomic_long_inc(&nfsi->redirtied_pages);
     nfs_end_page_writeback(req);
     nfs_release_request(req);
 }
 
 static void nfs_async_write_error(struct list_head *head, int error)
 {
     struct nfs_page *req;
 
     while (!list_empty(head)) {
         req = nfs_list_entry(head->next);
         nfs_list_remove_request(req);
         if (nfs_error_is_fatal_on_server(error))
             nfs_write_error(req, error);
         else
             nfs_redirty_request(req);
     }
 }
 
 static void nfs_async_write_reschedule_io(struct nfs_pgio_header *hdr)
 {
     nfs_async_write_error(&hdr->pages, 0);
 }
 
 static const struct nfs_pgio_completion_ops nfs_async_write_completion_ops = {
     .init_hdr = nfs_async_write_init,
     .error_cleanup = nfs_async_write_error,
     .completion = nfs_write_completion,
     .reschedule_io = nfs_async_write_reschedule_io,
 };
 
 void nfs_pageio_init_write(struct nfs_pageio_descriptor *pgio,
                    struct inode *inode, int ioflags, bool force_mds,
                    const struct nfs_pgio_completion_ops *compl_ops)
 {
     struct nfs_server *server = NFS_SERVER(inode);
     const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;
 
 #ifdef CONFIG_NFS_V4_1
     if (server->pnfs_curr_ld && !force_mds)
         pg_ops = server->pnfs_curr_ld->pg_write_ops;
 #endif
     nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_write_ops,
             server->wsize, ioflags);
 }
 EXPORT_SYMBOL_GPL(nfs_pageio_init_write);
 
 void nfs_pageio_reset_write_mds(struct nfs_pageio_descriptor *pgio)
 {
     struct nfs_pgio_mirror *mirror;
 
     if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
         pgio->pg_ops->pg_cleanup(pgio);
 
     pgio->pg_ops = &nfs_pgio_rw_ops;
 
     nfs_pageio_stop_mirroring(pgio);
 
     mirror = &pgio->pg_mirrors[0];
     mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->wsize;
 }
 EXPORT_SYMBOL_GPL(nfs_pageio_reset_write_mds);
 
 
 void nfs_commit_prepare(struct rpc_task *task, void *calldata)
 {
     struct nfs_commit_data *data = calldata;
 
     NFS_PROTO(data->inode)->commit_rpc_prepare(task, data);
 }
 
 static void nfs_writeback_check_extend(struct nfs_pgio_header *hdr,
         struct nfs_fattr *fattr)
 {
     struct nfs_pgio_args *argp = &hdr->args;
     struct nfs_pgio_res *resp = &hdr->res;
     u64 size = argp->offset + resp->count;
 
     if (!(fattr->valid & NFS_ATTR_FATTR_SIZE))
         fattr->size = size;
     if (nfs_size_to_loff_t(fattr->size) < i_size_read(hdr->inode)) {
         fattr->valid &= ~NFS_ATTR_FATTR_SIZE;
         return;
     }
     if (size != fattr->size)
         return;
     /* Set attribute barrier */
     nfs_fattr_set_barrier(fattr);
     /* ...and update size */
     fattr->valid |= NFS_ATTR_FATTR_SIZE;
 }
 
 void nfs_writeback_update_inode(struct nfs_pgio_header *hdr)
 {
     struct nfs_fattr *fattr = &hdr->fattr;
     struct inode *inode = hdr->inode;
 
     spin_lock(&inode->i_lock);
     nfs_writeback_check_extend(hdr, fattr);
     nfs_post_op_update_inode_force_wcc_locked(inode, fattr);
     spin_unlock(&inode->i_lock);
 }
 EXPORT_SYMBOL_GPL(nfs_writeback_update_inode);
 
 /*
  * This function is called when the WRITE call is complete.
  */
 static int nfs_writeback_done(struct rpc_task *task,
                   struct nfs_pgio_header *hdr,
                   struct inode *inode)
 {
     int status;
 
     /*
      * ->write_done will attempt to use post-op attributes to detect
      * conflicting writes by other clients.  A strict interpretation
      * of close-to-open would allow us to continue caching even if
      * another writer had changed the file, but some applications
      * depend on tighter cache coherency when writing.
      */
     status = NFS_PROTO(inode)->write_done(task, hdr);
     if (status != 0)
         return status;
 
     nfs_add_stats(inode, NFSIOS_SERVERWRITTENBYTES, hdr->res.count);
     trace_nfs_writeback_done(task, hdr);
 
     if (task->tk_status >= 0) {
         enum nfs3_stable_how committed = hdr->res.verf->committed;
 
         if (committed == NFS_UNSTABLE) {
             /*
              * We have some uncommitted data on the server at
              * this point, so ensure that we keep track of that
              * fact irrespective of what later writes do.
              */
             set_bit(NFS_IOHDR_UNSTABLE_WRITES, &hdr->flags);
         }
 
         if (committed < hdr->args.stable) {
             /* We tried a write call, but the server did not
              * commit data to stable storage even though we
              * requested it.
              * Note: There is a known bug in Tru64 < 5.0 in which
              *   the server reports NFS_DATA_SYNC, but performs
              *   NFS_FILE_SYNC. We therefore implement this checking
              *   as a dprintk() in order to avoid filling syslog.
              */
             static unsigned long    complain;
 
             /* Note this will print the MDS for a DS write */
             if (time_before(complain, jiffies)) {
                 dprintk("NFS:       faulty NFS server %s:"
                     " (committed = %d) != (stable = %d)\n",
                     NFS_SERVER(inode)->nfs_client->cl_hostname,
                     committed, hdr->args.stable);
                 complain = jiffies + 300 * HZ;
             }
         }
     }
 
     /* Deal with the suid/sgid bit corner case */
     if (nfs_should_remove_suid(inode)) {
         spin_lock(&inode->i_lock);
         nfs_set_cache_invalid(inode, NFS_INO_INVALID_MODE);
         spin_unlock(&inode->i_lock);
     }
     return 0;
 }
 
 /*
  * This function is called when the WRITE call is complete.
  */
 static void nfs_writeback_result(struct rpc_task *task,
                  struct nfs_pgio_header *hdr)
 {
     struct nfs_pgio_args    *argp = &hdr->args;
     struct nfs_pgio_res *resp = &hdr->res;
 
     if (resp->count < argp->count) {
         static unsigned long    complain;
 
         /* This a short write! */
         nfs_inc_stats(hdr->inode, NFSIOS_SHORTWRITE);
 
         /* Has the server at least made some progress? */
         if (resp->count == 0) {
             if (time_before(complain, jiffies)) {
                 printk(KERN_WARNING
                        "NFS: Server wrote zero bytes, expected %u.\n",
                        argp->count);
                 complain = jiffies + 300 * HZ;
             }
             nfs_set_pgio_error(hdr, -EIO, argp->offset);
             task->tk_status = -EIO;
             return;
         }
 
         /* For non rpc-based layout drivers, retry-through-MDS */
         if (!task->tk_ops) {
             hdr->pnfs_error = -EAGAIN;
             return;
         }
 
         /* Was this an NFSv2 write or an NFSv3 stable write? */
         if (resp->verf->committed != NFS_UNSTABLE) {
             /* Resend from where the server left off */
             hdr->mds_offset += resp->count;
             argp->offset += resp->count;
             argp->pgbase += resp->count;
             argp->count -= resp->count;
         } else {
             /* Resend as a stable write in order to avoid
              * headaches in the case of a server crash.
              */
             argp->stable = NFS_FILE_SYNC;
         }
         resp->count = 0;
         resp->verf->committed = 0;
         rpc_restart_call_prepare(task);
     }
 }
 
 static int wait_on_commit(struct nfs_mds_commit_info *cinfo)
 {
     return wait_var_event_killable(&cinfo->rpcs_out,
                        !atomic_read(&cinfo->rpcs_out));
 }
 
 static void nfs_commit_begin(struct nfs_mds_commit_info *cinfo)
 {
     atomic_inc(&cinfo->rpcs_out);
 }
 
 bool nfs_commit_end(struct nfs_mds_commit_info *cinfo)
 {
     if (atomic_dec_and_test(&cinfo->rpcs_out)) {
         wake_up_var(&cinfo->rpcs_out);
         return true;
     }
     return false;
 }
 
 void nfs_commitdata_release(struct nfs_commit_data *data)
 {
     put_nfs_open_context(data->context);
     nfs_commit_free(data);
 }
 EXPORT_SYMBOL_GPL(nfs_commitdata_release);
 
 int nfs_initiate_commit(struct rpc_clnt *clnt, struct nfs_commit_data *data,
             const struct nfs_rpc_ops *nfs_ops,
             const struct rpc_call_ops *call_ops,
             int how, int flags)
 {
     struct rpc_task *task;
     int priority = flush_task_priority(how);
     struct rpc_message msg = {
         .rpc_argp = &data->args,
         .rpc_resp = &data->res,
         .rpc_cred = data->cred,
     };
     struct rpc_task_setup task_setup_data = {
         .task = &data->task,
         .rpc_client = clnt,
         .rpc_message = &msg,
         .callback_ops = call_ops,
         .callback_data = data,
         .workqueue = nfsiod_workqueue,
         .flags = RPC_TASK_ASYNC | flags,
         .priority = priority,
     };
 
     if (nfs_server_capable(data->inode, NFS_CAP_MOVEABLE))
         task_setup_data.flags |= RPC_TASK_MOVEABLE;
 
     /* Set up the initial task struct.  */
     nfs_ops->commit_setup(data, &msg, &task_setup_data.rpc_client);
     trace_nfs_initiate_commit(data);
 
     dprintk("NFS: initiated commit call\n");
 
     task = rpc_run_task(&task_setup_data);
     if (IS_ERR(task))
         return PTR_ERR(task);
     if (how & FLUSH_SYNC)
         rpc_wait_for_completion_task(task);
     rpc_put_task(task);
     return 0;
 }
 EXPORT_SYMBOL_GPL(nfs_initiate_commit);
 
 static loff_t nfs_get_lwb(struct list_head *head)
 {
     loff_t lwb = 0;
     struct nfs_page *req;
 
     list_for_each_entry(req, head, wb_list)
         if (lwb < (req_offset(req) + req->wb_bytes))
             lwb = req_offset(req) + req->wb_bytes;
 
     return lwb;
 }
 
 /*
  * Set up the argument/result storage required for the RPC call.
  */
 void nfs_init_commit(struct nfs_commit_data *data,
              struct list_head *head,
              struct pnfs_layout_segment *lseg,
              struct nfs_commit_info *cinfo)
 {
     struct nfs_page *first;
     struct nfs_open_context *ctx;
     struct inode *inode;
 
     /* Set up the RPC argument and reply structs
      * NB: take care not to mess about with data->commit et al. */
 
     if (head)
         list_splice_init(head, &data->pages);
 
     first = nfs_list_entry(data->pages.next);
     ctx = nfs_req_openctx(first);
     inode = d_inode(ctx->dentry);
 
     data->inode   = inode;
     data->cred    = ctx->cred;
     data->lseg    = lseg; /* reference transferred */
     /* only set lwb for pnfs commit */
     if (lseg)
         data->lwb = nfs_get_lwb(&data->pages);
     data->mds_ops     = &nfs_commit_ops;
     data->completion_ops = cinfo->completion_ops;
     data->dreq    = cinfo->dreq;
 
     data->args.fh     = NFS_FH(data->inode);
     /* Note: we always request a commit of the entire inode */
     data->args.offset = 0;
     data->args.count  = 0;
     data->context     = get_nfs_open_context(ctx);
     data->res.fattr   = &data->fattr;
     data->res.verf    = &data->verf;
     nfs_fattr_init(&data->fattr);
     nfs_commit_begin(cinfo->mds);
 }
 EXPORT_SYMBOL_GPL(nfs_init_commit);
 
 void nfs_retry_commit(struct list_head *page_list,
               struct pnfs_layout_segment *lseg,
               struct nfs_commit_info *cinfo,
               u32 ds_commit_idx)
 {
     struct nfs_page *req;
 
     while (!list_empty(page_list)) {
         req = nfs_list_entry(page_list->next);
         nfs_list_remove_request(req);
         nfs_mark_request_commit(req, lseg, cinfo, ds_commit_idx);
         if (!cinfo->dreq)
             nfs_clear_page_commit(req->wb_page);
         nfs_unlock_and_release_request(req);
     }
 }
 EXPORT_SYMBOL_GPL(nfs_retry_commit);
 
 static void
 nfs_commit_resched_write(struct nfs_commit_info *cinfo,
         struct nfs_page *req)
 {
     __set_page_dirty_nobuffers(req->wb_page);
 }
 
 /*
  * Commit dirty pages
  */
 static int
 nfs_commit_list(struct inode *inode, struct list_head *head, int how,
         struct nfs_commit_info *cinfo)
 {
     struct nfs_commit_data  *data;
     unsigned short task_flags = 0;
 
     /* another commit raced with us */
     if (list_empty(head))
         return 0;
 
     data = nfs_commitdata_alloc();
     if (!data) {
         nfs_retry_commit(head, NULL, cinfo, -1);
         return -ENOMEM;
     }
 
     /* Set up the argument struct */
     nfs_init_commit(data, head, NULL, cinfo);
     if (NFS_SERVER(inode)->nfs_client->cl_minorversion)
         task_flags = RPC_TASK_MOVEABLE;
     return nfs_initiate_commit(NFS_CLIENT(inode), data, NFS_PROTO(inode),
                    data->mds_ops, how,
                    RPC_TASK_CRED_NOREF | task_flags);
 }
 
 /*
  * COMMIT call returned
  */
 static void nfs_commit_done(struct rpc_task *task, void *calldata)
 {
     struct nfs_commit_data  *data = calldata;
 
     /* Call the NFS version-specific code */
     NFS_PROTO(data->inode)->commit_done(task, data);
     trace_nfs_commit_done(task, data);
 }
 
 static void nfs_commit_release_pages(struct nfs_commit_data *data)
 {
     const struct nfs_writeverf *verf = data->res.verf;
     struct nfs_page *req;
     int status = data->task.tk_status;
     struct nfs_commit_info cinfo;
     struct nfs_server *nfss;
 
     while (!list_empty(&data->pages)) {
         req = nfs_list_entry(data->pages.next);
         nfs_list_remove_request(req);
         if (req->wb_page)
             nfs_clear_page_commit(req->wb_page);
 
         dprintk("NFS:       commit (%s/%llu %d@%lld)",
             nfs_req_openctx(req)->dentry->d_sb->s_id,
             (unsigned long long)NFS_FILEID(d_inode(nfs_req_openctx(req)->dentry)),
             req->wb_bytes,
             (long long)req_offset(req));
         if (status < 0) {
             if (req->wb_page) {
                 trace_nfs_commit_error(data->inode, req,
                                status);
                 nfs_mapping_set_error(req->wb_page, status);
                 nfs_inode_remove_request(req);
             }
             dprintk_cont(", error = %d\n", status);
             goto next;
         }
 
         /* Okay, COMMIT succeeded, apparently. Check the verifier
          * returned by the server against all stored verfs. */
         if (nfs_write_match_verf(verf, req)) {
             /* We have a match */
             if (req->wb_page)
                 nfs_inode_remove_request(req);
             dprintk_cont(" OK\n");
             goto next;
         }
         /* We have a mismatch. Write the page again */
         dprintk_cont(" mismatch\n");
         nfs_mark_request_dirty(req);
         atomic_long_inc(&NFS_I(data->inode)->redirtied_pages);
     next:
         nfs_unlock_and_release_request(req);
         /* Latency breaker */
         cond_resched();
     }
     nfss = NFS_SERVER(data->inode);
     if (atomic_long_read(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)
         nfss->write_congested = 0;
 
     nfs_init_cinfo(&cinfo, data->inode, data->dreq);
     nfs_commit_end(cinfo.mds);
 }
 
 static void nfs_commit_release(void *calldata)
 {
     struct nfs_commit_data *data = calldata;
 
     data->completion_ops->completion(data);
     nfs_commitdata_release(calldata);
 }
 
 static const struct rpc_call_ops nfs_commit_ops = {
     .rpc_call_prepare = nfs_commit_prepare,
     .rpc_call_done = nfs_commit_done,
     .rpc_release = nfs_commit_release,
 };
 
 static const struct nfs_commit_completion_ops nfs_commit_completion_ops = {
     .completion = nfs_commit_release_pages,
     .resched_write = nfs_commit_resched_write,
 };
 
 int nfs_generic_commit_list(struct inode *inode, struct list_head *head,
                 int how, struct nfs_commit_info *cinfo)
 {
     int status;
 
     status = pnfs_commit_list(inode, head, how, cinfo);
     if (status == PNFS_NOT_ATTEMPTED)
         status = nfs_commit_list(inode, head, how, cinfo);
     return status;
 }
 
 static int __nfs_commit_inode(struct inode *inode, int how,
         struct writeback_control *wbc)
 {
     LIST_HEAD(head);
     struct nfs_commit_info cinfo;
     int may_wait = how & FLUSH_SYNC;
     int ret, nscan;
 
     how &= ~FLUSH_SYNC;
     nfs_init_cinfo_from_inode(&cinfo, inode);
     nfs_commit_begin(cinfo.mds);
     for (;;) {
         ret = nscan = nfs_scan_commit(inode, &head, &cinfo);
         if (ret <= 0)
             break;
         ret = nfs_generic_commit_list(inode, &head, how, &cinfo);
         if (ret < 0)
             break;
         ret = 0;
         if (wbc && wbc->sync_mode == WB_SYNC_NONE) {
             if (nscan < wbc->nr_to_write)
                 wbc->nr_to_write -= nscan;
             else
                 wbc->nr_to_write = 0;
         }
         if (nscan < INT_MAX)
             break;
         cond_resched();
     }
     nfs_commit_end(cinfo.mds);
     if (ret || !may_wait)
         return ret;
     return wait_on_commit(cinfo.mds);
 }
 
 int nfs_commit_inode(struct inode *inode, int how)
 {
     return __nfs_commit_inode(inode, how, NULL);
 }
 EXPORT_SYMBOL_GPL(nfs_commit_inode);
 
 int nfs_write_inode(struct inode *inode, struct writeback_control *wbc)
 {
     struct nfs_inode *nfsi = NFS_I(inode);
     int flags = FLUSH_SYNC;
     int ret = 0;
 
     if (wbc->sync_mode == WB_SYNC_NONE) {
         /* no commits means nothing needs to be done */
         if (!atomic_long_read(&nfsi->commit_info.ncommit))
             goto check_requests_outstanding;
 
         /* Don't commit yet if this is a non-blocking flush and there
          * are a lot of outstanding writes for this mapping.
          */
         if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK))
             goto out_mark_dirty;
 
         /* don't wait for the COMMIT response */
         flags = 0;
     }
 
     ret = __nfs_commit_inode(inode, flags, wbc);
     if (!ret) {
         if (flags & FLUSH_SYNC)
             return 0;
     } else if (atomic_long_read(&nfsi->commit_info.ncommit))
         goto out_mark_dirty;
 
 check_requests_outstanding:
     if (!atomic_read(&nfsi->commit_info.rpcs_out))
         return ret;
 out_mark_dirty:
     __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
     return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_write_inode);
 
 /*
  * Wrapper for filemap_write_and_wait_range()
  *
  * Needed for pNFS in order to ensure data becomes visible to the
  * client.
  */
 int nfs_filemap_write_and_wait_range(struct address_space *mapping,
         loff_t lstart, loff_t lend)
 {
     int ret;
 
     ret = filemap_write_and_wait_range(mapping, lstart, lend);
     if (ret == 0)
         ret = pnfs_sync_inode(mapping->host, true);
     return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_filemap_write_and_wait_range);
 
 /*
  * flush the inode to disk.
  */
 int nfs_wb_all(struct inode *inode)
 {
     int ret;
 
     trace_nfs_writeback_inode_enter(inode);
 
     ret = filemap_write_and_wait(inode->i_mapping);
     if (ret)
         goto out;
     ret = nfs_commit_inode(inode, FLUSH_SYNC);
     if (ret < 0)
         goto out;
     pnfs_sync_inode(inode, true);
     ret = 0;
 
 out:
     trace_nfs_writeback_inode_exit(inode, ret);
     return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_wb_all);
 
 int nfs_wb_folio_cancel(struct inode *inode, struct folio *folio)
 {
     struct nfs_page *req;
     int ret = 0;
 
     folio_wait_writeback(folio);
 
     /* blocking call to cancel all requests and join to a single (head)
      * request */
     req = nfs_lock_and_join_requests(&folio->page);
 
     if (IS_ERR(req)) {
         ret = PTR_ERR(req);
     } else if (req) {
         /* all requests from this folio have been cancelled by
          * nfs_lock_and_join_requests, so just remove the head
          * request from the inode / page_private pointer and
          * release it */
         nfs_inode_remove_request(req);
         nfs_unlock_and_release_request(req);
     }
 
     return ret;
 }
 
 /*
  * Write back all requests on one page - we do this before reading it.
  */
 int nfs_wb_page(struct inode *inode, struct page *page)
 {
     loff_t range_start = page_file_offset(page);
     loff_t range_end = range_start + (loff_t)(PAGE_SIZE - 1);
     struct writeback_control wbc = {
         .sync_mode = WB_SYNC_ALL,
         .nr_to_write = 0,
         .range_start = range_start,
         .range_end = range_end,
     };
     int ret;
 
     trace_nfs_writeback_page_enter(inode);
 
     for (;;) {
         wait_on_page_writeback(page);
         if (clear_page_dirty_for_io(page)) {
             ret = nfs_writepage_locked(page, &wbc);
             if (ret < 0)
                 goto out_error;
             continue;
         }
         ret = 0;
         if (!PagePrivate(page))
             break;
         ret = nfs_commit_inode(inode, FLUSH_SYNC);
         if (ret < 0)
             goto out_error;
     }
 out_error:
     trace_nfs_writeback_page_exit(inode, ret);
     return ret;
 }
 
 #ifdef CONFIG_MIGRATION
 int nfs_migrate_folio(struct address_space *mapping, struct folio *dst,
         struct folio *src, enum migrate_mode mode)
 {
     /*
      * If the private flag is set, the folio is currently associated with
      * an in-progress read or write request. Don't try to migrate it.
      *
      * FIXME: we could do this in principle, but we'll need a way to ensure
      *        that we can safely release the inode reference while holding
      *        the folio lock.
      */
     if (folio_test_private(src))
         return -EBUSY;
 
     if (folio_test_fscache(src)) {
         if (mode == MIGRATE_ASYNC)
             return -EBUSY;
         folio_wait_fscache(src);
     }
 
     return migrate_folio(mapping, dst, src, mode);
 }
 #endif
 
 int __init nfs_init_writepagecache(void)
 {
     nfs_wdata_cachep = kmem_cache_create("nfs_write_data",
                          sizeof(struct nfs_pgio_header),
                          0, SLAB_HWCACHE_ALIGN,
                          NULL);
     if (nfs_wdata_cachep == NULL)
         return -ENOMEM;
 
     nfs_wdata_mempool = mempool_create_slab_pool(MIN_POOL_WRITE,
                              nfs_wdata_cachep);
     if (nfs_wdata_mempool == NULL)
         goto out_destroy_write_cache;
 
     nfs_cdata_cachep = kmem_cache_create("nfs_commit_data",
                          sizeof(struct nfs_commit_data),
                          0, SLAB_HWCACHE_ALIGN,
                          NULL);
     if (nfs_cdata_cachep == NULL)
         goto out_destroy_write_mempool;
 
     nfs_commit_mempool = mempool_create_slab_pool(MIN_POOL_COMMIT,
                               nfs_cdata_cachep);
     if (nfs_commit_mempool == NULL)
         goto out_destroy_commit_cache;
 
     /*
      * NFS congestion size, scale with available memory.
      *
      *  64MB:    8192k
      * 128MB:   11585k
      * 256MB:   16384k
      * 512MB:   23170k
      *   1GB:   32768k
      *   2GB:   46340k
      *   4GB:   65536k
      *   8GB:   92681k
      *  16GB:  131072k
      *
      * This allows larger machines to have larger/more transfers.
      * Limit the default to 256M
      */
     nfs_congestion_kb = (16*int_sqrt(totalram_pages())) << (PAGE_SHIFT-10);
     if (nfs_congestion_kb > 256*1024)
         nfs_congestion_kb = 256*1024;
 
     return 0;
 
 out_destroy_commit_cache:
     kmem_cache_destroy(nfs_cdata_cachep);
 out_destroy_write_mempool:
     mempool_destroy(nfs_wdata_mempool);
 out_destroy_write_cache:
     kmem_cache_destroy(nfs_wdata_cachep);
     return -ENOMEM;
 }
 
 void nfs_destroy_writepagecache(void)
 {
     mempool_destroy(nfs_commit_mempool);
     kmem_cache_destroy(nfs_cdata_cachep);
     mempool_destroy(nfs_wdata_mempool);
     kmem_cache_destroy(nfs_wdata_cachep);
 }
 
 static const struct nfs_rw_ops nfs_rw_write_ops = {
     .rw_alloc_header    = nfs_writehdr_alloc,
     .rw_free_header     = nfs_writehdr_free,
     .rw_done        = nfs_writeback_done,
     .rw_result      = nfs_writeback_result,
     .rw_initiate        = nfs_initiate_write,
 };

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