https://github.com/torvalds/linux
Revision 0aeea18964173715a1037034ef6838198f319319 authored by Lukas Czerner on 11 March 2011, 09:23:53 UTC, committed by Jens Axboe on 11 March 2011, 14:36:08 UTC
BZ29402 https://bugzilla.kernel.org/show_bug.cgi?id=29402 We can hit serious mis-synchronization in bio completion path of blkdev_issue_zeroout() leading to a panic. The problem is that when we are going to wait_for_completion() in blkdev_issue_zeroout() we check if the bb.done equals issued (number of submitted bios). If it does, we can skip the wait_for_completition() and just out of the function since there is nothing to wait for. However, there is a ordering problem because bio_batch_end_io() is calling atomic_inc(&bb->done) before complete(), hence it might seem to blkdev_issue_zeroout() that all bios has been completed and exit. At this point when bio_batch_end_io() is going to call complete(bb->wait), bb and wait does not longer exist since it was allocated on stack in blkdev_issue_zeroout() ==> panic! (thread 1) (thread 2) bio_batch_end_io() blkdev_issue_zeroout() if(bb) { ... if (bb->end_io) ... bb->end_io(bio, err); ... atomic_inc(&bb->done); ... ... while (issued != atomic_read(&bb.done)) ... (let issued == bb.done) ... (do the rest of the function) ... return ret; complete(bb->wait); ^^^^^^^^ panic We can fix this easily by simplifying bio_batch and completion counting. Also remove bio_end_io_t *end_io since it is not used. Signed-off-by: Lukas Czerner <lczerner@redhat.com> Reported-by: Eric Whitney <eric.whitney@hp.com> Tested-by: Eric Whitney <eric.whitney@hp.com> Reviewed-by: Jeff Moyer <jmoyer@redhat.com> CC: Dmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
1 parent 9179746
Tip revision: 0aeea18964173715a1037034ef6838198f319319 authored by Lukas Czerner on 11 March 2011, 09:23:53 UTC
block: fix mis-synchronisation in blkdev_issue_zeroout()
block: fix mis-synchronisation in blkdev_issue_zeroout()
Tip revision: 0aeea18
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drivers | ||
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include | ||
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kernel | ||
lib | ||
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net | ||
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COPYING | -rw-r--r-- | 18.3 KB |
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Kbuild | -rw-r--r-- | 2.4 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 187.4 KB |
Makefile | -rw-r--r-- | 50.9 KB |
README | -rw-r--r-- | 17.1 KB |
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