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| author | Mike Snitzer <snitzer@redhat.com> | 2011-07-06 21:30:50 +0200 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2011-07-06 21:32:02 +0200 |
| commit | 0f79960391a5a1e3679956024e18aeeb0369ac44 (patch) | |
| tree | 4b7e1f7a2b24f3307259024a5f29dbdc0f8b7bd2 /block | |
| parent | 390192b300570b2bc721d77067ca133f58015ae8 (diff) | |
| download | lwn-0f79960391a5a1e3679956024e18aeeb0369ac44.tar.gz lwn-0f79960391a5a1e3679956024e18aeeb0369ac44.zip | |
block: eliminate potential for infinite loop in blkdev_issue_discard
Due to the recently identified overflow in read_capacity_16() it was
possible for max_discard_sectors to be zero but still have discards
enabled on the associated device's queue.
Eliminate the possibility for blkdev_issue_discard to infinitely loop.
Interestingly this issue wasn't identified until a device, whose
discard_granularity was 0 due to read_capacity_16 overflow, was consumed
by blk_stack_limits() to construct limits for a higher-level DM
multipath device. The multipath device's resulting limits never had the
discard limits stacked because blk_stack_limits() will only do so if
the bottom device's discard_granularity != 0. This resulted in the
multipath device's limits.max_discard_sectors being 0.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-lib.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/block/blk-lib.c b/block/blk-lib.c index 78e627e2581d..64974b1c7cca 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -59,7 +59,10 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, * granularity */ max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9); - if (q->limits.discard_granularity) { + if (!unlikely(!max_discard_sectors)) { + /* Avoid infinite loop below. Being cautious never hurts. */ + return -EOPNOTSUPP; + } else if (q->limits.discard_granularity) { unsigned int disc_sects = q->limits.discard_granularity >> 9; max_discard_sectors &= ~(disc_sects - 1); |