fix error inversion problems with data flushing 

From: Dave Chinner <david@fromorbit.com>

XFS gets the sign of the error wrong in several places when
gathering the error from generic linux functions. These functions
return negative error values, while the core XFS code returns
positive error values. Hence when XFS inverts the error to be
returned to the VFS, it can incorrectly invert a negative
error and this error will be ignored by the syscall return.

Fix all the problems related to calling filemap_* functions.

Problem initially identified by Nick Piggin in xfs_fsync().

Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

---
 fs/xfs/linux-2.6/xfs_fs_subr.c |   23 ++++++++++++++++++++---
 fs/xfs/linux-2.6/xfs_lrw.c     |    2 +-
 fs/xfs/linux-2.6/xfs_super.c   |   13 +++++++++----
 fs/xfs/xfs_vnodeops.c          |    2 +-
 fs/xfs/xfs_vnodeops.h          |    1 +
 5 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_fs_subr.c b/fs/xfs/linux-2.6/xfs_fs_subr.c
index 36caa6d..5aeb777 100644
--- a/fs/xfs/linux-2.6/xfs_fs_subr.c
+++ b/fs/xfs/linux-2.6/xfs_fs_subr.c
@@ -24,6 +24,10 @@ int  fs_noerr(void) { return 0; }
 int  fs_nosys(void) { return ENOSYS; }
 void fs_noval(void) { return; }
 
+/*
+ * note: all filemap functions return negative error codes. These
+ * need to be inverted before returning to the xfs core functions.
+ */
 void
 xfs_tosspages(
 	xfs_inode_t	*ip,
@@ -53,7 +57,7 @@ xfs_flushinval_pages(
 		if (!ret)
 			truncate_inode_pages(mapping, first);
 	}
-	return ret;
+	return -ret;
 }
 
 int
@@ -72,10 +76,23 @@ xfs_flush_pages(
 		xfs_iflags_clear(ip, XFS_ITRUNCATED);
 		ret = filemap_fdatawrite(mapping);
 		if (flags & XFS_B_ASYNC)
-			return ret;
+			return -ret;
 		ret2 = filemap_fdatawait(mapping);
 		if (!ret)
 			ret = ret2;
 	}
-	return ret;
+	return -ret;
+}
+
+int
+xfs_wait_on_pages(
+	xfs_inode_t	*ip,
+	xfs_off_t	first,
+	xfs_off_t	last)
+{
+	struct address_space *mapping = VFS_I(ip)->i_mapping;
+
+	if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
+		return -filemap_fdatawait(mapping);
+	return 0;
 }
diff --git a/fs/xfs/linux-2.6/xfs_lrw.c b/fs/xfs/linux-2.6/xfs_lrw.c
index 1957e53..4959c87 100644
--- a/fs/xfs/linux-2.6/xfs_lrw.c
+++ b/fs/xfs/linux-2.6/xfs_lrw.c
@@ -243,7 +243,7 @@ xfs_read(
 
 	if (unlikely(ioflags & IO_ISDIRECT)) {
 		if (inode->i_mapping->nrpages)
-			ret = xfs_flushinval_pages(ip, (*offset & PAGE_CACHE_MASK),
+			ret = -xfs_flushinval_pages(ip, (*offset & PAGE_CACHE_MASK),
 						    -1, FI_REMAPF_LOCKED);
 		mutex_unlock(&inode->i_mutex);
 		if (ret) {
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 9dc977d..c5cfc1e 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -1012,21 +1012,26 @@ xfs_fs_write_inode(
 	struct inode		*inode,
 	int			sync)
 {
+	struct xfs_inode	*ip = XFS_I(inode);
 	int			error = 0;
 	int			flags = 0;
 
-	xfs_itrace_entry(XFS_I(inode));
+	xfs_itrace_entry(ip);
 	if (sync) {
-		filemap_fdatawait(inode->i_mapping);
+		error = xfs_wait_on_pages(ip, 0, -1);
+		if (error)
+			goto out_error;
 		flags |= FLUSH_SYNC;
 	}
-	error = xfs_inode_flush(XFS_I(inode), flags);
+	error = xfs_inode_flush(ip, flags);
+
+out_error:
 	/*
 	 * if we failed to write out the inode then mark
 	 * it dirty again so we'll try again later.
 	 */
 	if (error)
-		xfs_mark_inode_dirty_sync(XFS_I(inode));
+		xfs_mark_inode_dirty_sync(ip);
 
 	return -error;
 }
diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 2e2fbd9..5809c42 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -713,7 +713,7 @@ xfs_fsync(
 		return XFS_ERROR(EIO);
 
 	/* capture size updates in I/O completion before writing the inode. */
-	error = filemap_fdatawait(VFS_I(ip)->i_mapping);
+	error = xfs_wait_on_pages(ip, 0, -1);
 	if (error)
 		return XFS_ERROR(error);
 
diff --git a/fs/xfs/xfs_vnodeops.h b/fs/xfs/xfs_vnodeops.h
index e932a96..f9cd376 100644
--- a/fs/xfs/xfs_vnodeops.h
+++ b/fs/xfs/xfs_vnodeops.h
@@ -78,5 +78,6 @@ int xfs_flushinval_pages(struct xfs_inode *ip, xfs_off_t first,
 		xfs_off_t last, int fiopt);
 int xfs_flush_pages(struct xfs_inode *ip, xfs_off_t first,
 		xfs_off_t last, uint64_t flags, int fiopt);
+int xfs_wait_on_pages(struct xfs_inode *ip, xfs_off_t first, xfs_off_t last);
 
 #endif /* _XFS_VNODEOPS_H */
-- 
1.5.6.5