NFS - fix recent breakage to NFS error handling.

From c6d615d2b97fe305cbf123a8751ced859dca1d5e Mon Sep 17 00:00:00 2001
From: NeilBrown <[email protected]>
Date: Wed, 16 Nov 2011 09:39:05 +1100
Subject: [PATCH] NFS - fix recent breakage to NFS error handling.

commit 02c24a82187d5a628c68edfe71ae60dc135cd178 made a small and presumably unintended change to write error handling in NFS.

Previously an error from filemap_write_and_wait_range would only be of interest if nfs_file_fsync did not return an error. After this commit, an error from filemap_write_and_wait_range would mean that (the rest of) nfs_file_fsync would not even be called.

This means that:
1/ you are more likely to see EIO than e.g. EDQUOT or ENOSPC. 2/ NFS_CONTEXT_ERROR_WRITE remains set for longer so more writes are
synchronous.

This patch restores previous behaviour.

---
 fs/nfs/file.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

index 0a1f831..3099d55 100644
@@ -312,13 +312,13 @@ nfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 			datasync);
 
 	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
-	if (ret)
-		return ret;
 	mutex_lock(&inode->i_mutex);
 
 	nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
 	have_error = test_and_clear_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
 	status = nfs_commit_inode(inode, FLUSH_SYNC);
+	if (status >= 0 && ret < 0)
+		status = ret;
 	have_error |= test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
 	if (have_error)
 		ret = xchg(&ctx->error, 0);

1.7.7.3

Do we need more consideration on commit 02c24a82187d5a628c68edfe71ae60dc135cd178?
Before it, vfs_fsync_range() calls f_op->fsync() regardless of filemap_write_and_wait_range() errors. After commit 02c24a82187d5a628c68edfe71ae60dc135cd178, it only calls f_op->fsync() when filemap_write_end_and_wait_range() succeeds. So the change is not really trivial to all file systems.

Thanks,
Tao

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