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>
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390192b300
Коммит
0f79960391
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@ -59,7 +59,10 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
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* granularity
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*/
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max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
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if (q->limits.discard_granularity) {
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if (!unlikely(!max_discard_sectors)) {
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/* Avoid infinite loop below. Being cautious never hurts. */
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return -EOPNOTSUPP;
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} else if (q->limits.discard_granularity) {
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unsigned int disc_sects = q->limits.discard_granularity >> 9;
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max_discard_sectors &= ~(disc_sects - 1);
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