[XFS] Map unwritten extents correctly for I/o completion processing

If we have multiple unwritten extents within a single page, we fail to
tell the I/o completion construction handlers we need a new handle for the
second and subsequent blocks in the page. While we still issue the I/O
correctly, we do not have the correct ranges recorded in the ioend
structures and hence when we go to convert the unwritten extents we screw
it up.

Make sure we start a new ioend every time the mapping changes so that we
convert the correct ranges on I/O completion.

SGI-PV: 964647
SGI-Modid: xfs-linux-melb:xfs-kern:28797a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tim Shimmin <tes@sgi.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index c097e4e69768..fd4105d662e0 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -1010,6 +1010,8 @@ xfs_page_state_convert(
                 if (buffer_unwritten(bh) || buffer_delay(bh) ||
                     ((buffer_uptodate(bh) || PageUptodate(page)) &&
                      !buffer_mapped(bh) && (unmapped || startio))) {
+                        int new_ioend = 0;
+
                         /*
                          * Make sure we don't use a read-only iomap
                          */
@@ -1028,6 +1030,15 @@ xfs_page_state_convert(
                         }
 
                         if (!iomap_valid) {
+                                /*
+                                 * if we didn't have a valid mapping then we
+                                 * need to ensure that we put the new mapping
+                                 * in a new ioend structure. This needs to be
+                                 * done to ensure that the ioends correctly
+                                 * reflect the block mappings at io completion
+                                 * for unwritten extent conversion.
+                                 */
+                                new_ioend = 1;
                                 if (type == IOMAP_NEW) {
                                         size = xfs_probe_cluster(inode,
                                                         page, bh, head, 0);
@@ -1047,7 +1058,7 @@ xfs_page_state_convert(
                                 if (startio) {
                                         xfs_add_to_ioend(inode, bh, offset,
                                                         type, &ioend,
-                                                        !iomap_valid);
+                                                        new_ioend);
                                 } else {
                                         set_buffer_dirty(bh);
                                         unlock_buffer(bh);