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authorDavid Chinner <dgc@sgi.com>2006-01-18 13:38:12 +1100
committerNathan Scott <nathans@sgi.com>2006-01-18 13:38:12 +1100
commitd88992f660936049f5f38d74ea5a86b5c1491a48 (patch)
tree3c3ac2e25d33e4bd59193b9d4ecf7a1bee3e4d0e
parent2664b25051f7ab96b22b199aa2f5ef6a949a4296 (diff)
[XFS] Fix a race in xfs_submit_ioend() where we can be completing I/O for
a page while we are still submitting other buffers on the same page for I/O. SGI-PV: 948197 SGI-Modid: xfs-linux-melb:xfs-kern:25004a Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Nathan Scott <nathans@sgi.com>
-rw-r--r--fs/xfs/linux-2.6/xfs_aops.c29
1 files changed, 26 insertions, 3 deletions
diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index d1db8c17a74e..120626789406 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -336,24 +336,47 @@ static inline int bio_add_buffer(struct bio *bio, struct buffer_head *bh)
}
/*
- * Submit all of the bios for all of the ioends we have saved up,
- * covering the initial writepage page and also any probed pages.
+ * Submit all of the bios for all of the ioends we have saved up, covering the
+ * initial writepage page and also any probed pages.
+ *
+ * Because we may have multiple ioends spanning a page, we need to start
+ * writeback on all the buffers before we submit them for I/O. If we mark the
+ * buffers as we got, then we can end up with a page that only has buffers
+ * marked async write and I/O complete on can occur before we mark the other
+ * buffers async write.
+ *
+ * The end result of this is that we trip a bug in end_page_writeback() because
+ * we call it twice for the one page as the code in end_buffer_async_write()
+ * assumes that all buffers on the page are started at the same time.
+ *
+ * The fix is two passes across the ioend list - one to start writeback on the
+ * bufferheads, and then the second one submit them for I/O.
*/
STATIC void
xfs_submit_ioend(
xfs_ioend_t *ioend)
{
+ xfs_ioend_t *head = ioend;
xfs_ioend_t *next;
struct buffer_head *bh;
struct bio *bio;
sector_t lastblock = 0;
+ /* Pass 1 - start writeback */
+ do {
+ next = ioend->io_list;
+ for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {
+ xfs_start_buffer_writeback(bh);
+ }
+ } while ((ioend = next) != NULL);
+
+ /* Pass 2 - submit I/O */
+ ioend = head;
do {
next = ioend->io_list;
bio = NULL;
for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {
- xfs_start_buffer_writeback(bh);
if (!bio) {
retry: