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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>
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@ -1100,22 +1100,18 @@ xfs_bwrite(
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return error;
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}
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STATIC void
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static void
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xfs_buf_bio_end_io(
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struct bio *bio)
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{
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xfs_buf_t *bp = (xfs_buf_t *)bio->bi_private;
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struct xfs_buf *bp = (struct xfs_buf *)bio->bi_private;
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/*
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* don't overwrite existing errors - otherwise we can lose errors on
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* buffers that require multiple bios to complete.
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*/
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if (bio->bi_error) {
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spin_lock(&bp->b_lock);
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if (!bp->b_io_error)
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bp->b_io_error = bio->bi_error;
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spin_unlock(&bp->b_lock);
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}
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if (bio->bi_error)
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cmpxchg(&bp->b_io_error, 0, bio->bi_error);
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if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
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invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
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