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27 March 2024, 02:37:15 UTC
Revision fcb82f8835c1d71b4fe5de1d9894f45370f80dab authored by Zach Brown on 03 July 2007, 22:28:55 UTC, committed by Linus Torvalds on 04 July 2007, 01:23:23 UTC 
dio: remove bogus refcounting BUG_ON
 
Badari Pulavarty reported a case of this BUG_ON is triggering during
testing.  It's completely bogus and should be removed.

It's trying to notice if we left references to the dio hanging around in
the sync case.  They should have been dropped as IO completed while this
path was in dio_await_completion().  This condition will also be
checked, via some twisty logic, by the BUG_ON(ret != -EIOCBQUEUED) a few
lines lower.  So to start this BUG_ON() is redundant.

More fatally, it's dereferencing dio-> after having dropped its
reference.  It's only safe to dereference the dio after releasing the
lock if the final reference was just dropped.  Another CPU might free
the dio in bio completion and reuse the memory after this path drops the
dio lock but before the BUG_ON() is evaluated.

This patch passed aio+dio regression unit tests and aio-stress on ext3.

Signed-off-by: Zach Brown <zach.brown@oracle.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 5dcccd8
History
Tip revision: fcb82f8835c1d71b4fe5de1d9894f45370f80dab authored by Zach Brown on 03 July 2007, 22:28:55 UTC
dio: remove bogus refcounting BUG_ON
Tip revision: fcb82f8
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