Re: [PATCH v7 1/3] bio: limit bio max size
From: Bart Van Assche <bvanassche@acm.org>
Date: 2021-04-15 19:19:00
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On 4/15/21 3:38 AM, Changheun Lee wrote:
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@@ -167,6 +168,7 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto max_sectors = round_down(max_sectors, limits->logical_block_size >> SECTOR_SHIFT); limits->max_sectors = max_sectors; + limits->bio_max_bytes = max_sectors << SECTOR_SHIFT; q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9); }
Can the new shift operation overflow? If so, how about using check_shl_overflow()?
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@@ -538,6 +540,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, { unsigned int top, bottom, alignment, ret = 0; + t->bio_max_bytes = min_not_zero(t->bio_max_bytes, b->bio_max_bytes); + t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors); t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors); t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors);
The above will limit bio_max_bytes for all stacked block devices, which is something we do not want. I propose to set t->bio_max_bytes to UINT_MAX in blk_stack_limits() and to let the stacked driver (e.g. dm-crypt) decide whether or not to lower that value.
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diff --git a/include/linux/bio.h b/include/linux/bio.h index d0246c92a6e8..e5add63da3af 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h@@ -106,6 +106,8 @@ static inline void *bio_data(struct bio *bio) return NULL; } +extern unsigned int bio_max_size(struct bio *bio);
You may want to define bio_max_size() as an inline function in bio.h such that no additional function calls are introduced in the hot path. Thanks, Bart.