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authorDave Chinner <dchinner@redhat.com>2012-11-12 22:09:46 +1100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-11-26 11:37:36 -0800
commit0244d2ed647d788233ad72d32986bc0ee9a71d5b (patch)
tree1d5d58aca768824271ed6d039f69b11b9bedd44f /fs/xfs
parent3f874ecc49208f3635e29c3a08ade01778ad85e4 (diff)
xfs: drop buffer io reference when a bad bio is built
commit d69043c42d8c6414fa28ad18d99973aa6c1c2e24 upstream. Error handling in xfs_buf_ioapply_map() does not handle IO reference counts correctly. We increment the b_io_remaining count before building the bio, but then fail to decrement it in the failure case. This leads to the buffer never running IO completion and releasing the reference that the IO holds, so at unmount we can leak the buffer. This leak is captured by this assert failure during unmount: XFS: Assertion failed: atomic_read(&pag->pag_ref) == 0, file: fs/xfs/xfs_mount.c, line: 273 This is not a new bug - the b_io_remaining accounting has had this problem for a long, long time - it's just very hard to get a zero length bio being built by this code... Further, the buffer IO error can be overwritten on a multi-segment buffer by subsequent bio completions for partial sections of the buffer. Hence we should only set the buffer error status if the buffer is not already carrying an error status. This ensures that a partial IO error on a multi-segment buffer will not be lost. This part of the problem is a regression, however. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Mark Tinguely <tinguely@sgi.com> Signed-off-by: Ben Myers <bpm@sgi.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/xfs')
-rw-r--r--fs/xfs/xfs_buf.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 6819b5163e33..bb76128b5f47 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1165,9 +1165,14 @@ xfs_buf_bio_end_io(
{
xfs_buf_t *bp = (xfs_buf_t *)bio->bi_private;
- xfs_buf_ioerror(bp, -error);
+ /*
+ * don't overwrite existing errors - otherwise we can lose errors on
+ * buffers that require multiple bios to complete.
+ */
+ if (!bp->b_error)
+ xfs_buf_ioerror(bp, -error);
- if (!error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
+ if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
_xfs_buf_ioend(bp, 1);
@@ -1243,6 +1248,11 @@ next_chunk:
if (size)
goto next_chunk;
} else {
+ /*
+ * This is guaranteed not to be the last io reference count
+ * because the caller (xfs_buf_iorequest) holds a count itself.
+ */
+ atomic_dec(&bp->b_io_remaining);
xfs_buf_ioerror(bp, EIO);
bio_put(bio);
}