From: Brian Foster <bfoster@redhat.com>
To: xfs@oss.sgi.com
Subject: [PATCH] xfs: don't assert fail on non-async buffers on ioacct decrement
Date: Wed, 3 Aug 2016 12:12:53 -0400 [thread overview]
Message-ID: <1470240773-12850-1-git-send-email-bfoster@redhat.com> (raw)
The buffer I/O accounting mechanism tracks async buffers under I/O. As
an optimization, the buffer I/O count is incremented only once on the
first async I/O for a given hold cycle of a buffer and decremented once
the buffer is released to the LRU (or freed).
xfs_buf_ioacct_dec() has an ASSERT() check for an XBF_ASYNC buffer, but
we have one or two corner cases where a buffer can be submitted for I/O
multiple times via different methods in a single hold cycle. If an async
I/O occurs first, the I/O count is incremented. If a sync I/O occurs
before the hold count drops, XBF_ASYNC is cleared by the time the I/O
count is decremented.
Remove the async assert check from xfs_buf_ioacct_dec() as this is a
perfectly valid scenario. For the purposes of I/O accounting, we really
only care about the buffer async state at I/O submission time.
Discovered-and-analyzed-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Brian Foster <bfoster@redhat.com>
---
fs/xfs/xfs_buf.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 32fc540..b13ff61 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -115,7 +115,6 @@ xfs_buf_ioacct_dec(
if (!(bp->b_flags & _XBF_IN_FLIGHT))
return;
- ASSERT(bp->b_flags & XBF_ASYNC);
bp->b_flags &= ~_XBF_IN_FLIGHT;
percpu_counter_dec(&bp->b_target->bt_io_count);
}
--
2.5.5
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reply other threads:[~2016-08-03 16:12 UTC|newest]
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