NFS: Fix fdatasync/fsync() when confronted with a server reboot

If the server reboots before it can commit the unstable writes to disk,
then nfs_commit_release_pages() will detect this when it compares the
verifier returned by COMMIT to the one returned by WRITE. When this
happens, the client needs to resend those writes in order to guarantee
that they make it to stable storage.

This patch adds a signalling mechanism to notify fsync() that it
needs to retry all writes before it can exit.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 12 insertions, 10 deletions

diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index eb5eb8eef4d3..eef1b38a1b08 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -95,16 +95,18 @@ nfs4_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
         int ret;
         struct inode *inode = file->f_path.dentry->d_inode;
 
-        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
-        if (ret != 0)
-                goto out;
-        mutex_lock(&inode->i_mutex);
-        ret = nfs_file_fsync_commit(file, start, end, datasync);
-        if (!ret && !datasync)
-                /* application has asked for meta-data sync */
-                ret = pnfs_layoutcommit_inode(inode, true);
-        mutex_unlock(&inode->i_mutex);
-out:
+        do {
+                ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+                if (ret != 0)
+                        break;
+                mutex_lock(&inode->i_mutex);
+                ret = nfs_file_fsync_commit(file, start, end, datasync);
+                if (!ret && !datasync)
+                        /* application has asked for meta-data sync */
+                        ret = pnfs_layoutcommit_inode(inode, true);
+                mutex_unlock(&inode->i_mutex);
+        } while (ret == -EAGAIN);
+
         return ret;
 }