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block: cleanup and fix batch completion adding conditions

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The conditions for whether or not a request is allowed adding to a
completion batch are a bit hard to read, and they also have a few
issues. One is that ioerror may indeed be a random value on passthrough,
and it's being checked unconditionally of whether or not the given
request is a passthrough request or not.

Rewrite the conditions to be separate for easier reading, and only check
ioerror for non-passthrough requests. This fixes an issue with bio
unmapping on passthrough, where it fails getting added to a batch. This
both leads to suboptimal performance, and may trigger a potential
schedule-under-atomic condition for polled passthrough IO.

Fixes: f794f3351f ("block: add support for blk_mq_end_request_batch()")
Link: https://lore.kernel.org/r/20575f0a-656e-4bb3-9d82-dec6c7e3a35c@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2025-02-13 08:18:46 -07:00
parent 96b531f9bb
commit 1f47ed294a
1 changed files with 14 additions and 4 deletions
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18
include/linux/blk-mq.h
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@ -861,12 +861,22 @@ static inline bool blk_mq_add_to_batch(struct request *req,
void (*complete)(struct io_comp_batch *)) void (*complete)(struct io_comp_batch *))
{ {
/* /*
* blk_mq_end_request_batch() can't end request allocated from * Check various conditions that exclude batch processing:
* sched tags * 1) No batch container
* 2) Has scheduler data attached
* 3) Not a passthrough request and end_io set
* 4) Not a passthrough request and an ioerror
*/ */
if (!iob || (req->rq_flags & RQF_SCHED_TAGS) || ioerror || if (!iob)
(req->end_io && !blk_rq_is_passthrough(req)))
return false; return false;
if (req->rq_flags & RQF_SCHED_TAGS)
return false;
if (!blk_rq_is_passthrough(req)) {
if (req->end_io)
return false;
if (ioerror < 0)
return false;
}
if (!iob->complete) if (!iob->complete)
iob->complete = complete; iob->complete = complete;