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Restore the explanation for NOMERGES flag

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The comment was remved in 1e5355eba1

Signed-off-by: Michal Mielewczyk <michal.mielewczyk@huawei.com>
This commit is contained in:
Michal Mielewczyk 2024-09-20 09:25:52 +02:00
parent ae2d14dfb2
commit a1629790af
1 changed files with 8 additions and 0 deletions
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8
configure.d/1_queue_limits.conf
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@ -49,6 +49,14 @@ apply() {
exp_q->limits.max_write_same_sectors = 0;
}"
# A workaround for RHEL/CentOS 7.3 bug in kernel.
# Merging implementation on blk-mq does not respect virt boundary
# restriction and front merges bios with non-zero offsets.
# This leads to request with gaps between bios and in consequence
# triggers BUG_ON() in nvme driver or silently corrupts data.
# To prevent this, disable merging on cache queue if there are
# requirements regarding virt boundary (marking bios with REQ_NOMERGE
# does not solve this problem).
add_function "
static inline void cas_cache_set_no_merges_flag(struct request_queue *cache_q)
{