From 1f47ed294a2bd577d5ae43e6e28e1c9a3be4a833 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 13 Feb 2025 08:18:46 -0700
Subject: [PATCH] block: cleanup and fix batch completion adding conditions
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: f794f3351f26 ("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>
---
include/linux/blk-mq.h | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 9ebb53f031cdb..fa2a76cc2f73d 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -861,12 +861,22 @@ static inline bool blk_mq_add_to_batch(struct request *req,
void (*complete)(struct io_comp_batch *))
{
/*
- * blk_mq_end_request_batch() can't end request allocated from
- * sched tags
+ * Check various conditions that exclude batch processing:
+ * 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 ||
- (req->end_io && !blk_rq_is_passthrough(req)))
+ if (!iob)
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)
iob->complete = complete;
--
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