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authorBrian Foster <bfoster@redhat.com>2016-05-18 10:56:41 +1000
committerDave Chinner <david@fromorbit.com>2016-05-18 10:56:41 +1000
commit9bdd9bd69b826875531bb1b2efb6aeb8d70e6f72 (patch)
tree8cf9acecfa7280e4c3e43e116dc1f592665fa14b /fs/xfs
parentf55532a0c0b8bb6148f4e07853b876ef73bc69ca (diff)
downloadop-kernel-dev-9bdd9bd69b826875531bb1b2efb6aeb8d70e6f72.zip
op-kernel-dev-9bdd9bd69b826875531bb1b2efb6aeb8d70e6f72.tar.gz
xfs: buffer ->bi_end_io function requires irq-safe lock
Reports have surfaced of a lockdep splat complaining about an irq-safe -> irq-unsafe locking order in the xfs_buf_bio_end_io() bio completion handler. This only occurs when I/O errors are present because bp->b_lock is only acquired in this context to protect setting an error on the buffer. The problem is that this lock can be acquired with the (request_queue) q->queue_lock held. See scsi_end_request() or ata_qc_schedule_eh(), for example. Replace the locked test/set of b_io_error with a cmpxchg() call. This eliminates the need for the lock and thus the lock ordering problem goes away. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs')
-rw-r--r--fs/xfs/xfs_buf.c12
1 files changed, 4 insertions, 8 deletions
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 9a2191b..e71cfbd 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1100,22 +1100,18 @@ xfs_bwrite(
return error;
}
-STATIC void
+static void
xfs_buf_bio_end_io(
struct bio *bio)
{
- xfs_buf_t *bp = (xfs_buf_t *)bio->bi_private;
+ struct xfs_buf *bp = (struct xfs_buf *)bio->bi_private;
/*
* don't overwrite existing errors - otherwise we can lose errors on
* buffers that require multiple bios to complete.
*/
- if (bio->bi_error) {
- spin_lock(&bp->b_lock);
- if (!bp->b_io_error)
- bp->b_io_error = bio->bi_error;
- spin_unlock(&bp->b_lock);
- }
+ if (bio->bi_error)
+ cmpxchg(&bp->b_io_error, 0, bio->bi_error);
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));
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