linux-kernel - [PATCH] blk-iocost: skip empty flush bio in iocost

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230720121441.1408522-1-chengming.zhou@linux.dev>
Date:   Thu, 20 Jul 2023 20:14:41 +0800
From:   chengming.zhou@...ux.dev
To:     tj@...nel.org, josef@...icpanda.com
Cc:     axboe@...nel.dk, cgroups@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhouchengming@...edance.com
Subject: [PATCH] blk-iocost: skip empty flush bio in iocost

From: Chengming Zhou <zhouchengming@...edance.com>

The flush bio may have data, may have no data (empty flush), we couldn't
calculate cost for empty flush bio. So we'd better just skip it for now.

Another side effect is that empty flush bio's bio_end_sector() is 0, cause
iocg->cursor reset to 0, may break the cost calculation of other bios.

This isn't good enough, since flush bio still consume the device bandwidth,
but flush request is special, can be merged randomly in the flush state
machine, we don't know how to calculate cost for it for now.

Its completion time also has flaws, which may include the pre-flush or
post-flush completion time, but I don't know if we need to fix that and
how to fix it.

Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 block/blk-iocost.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 6084a9519883..e735b3e9997c 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2516,6 +2516,10 @@ static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg,
 	u64 seek_pages = 0;
 	u64 cost = 0;

+	/* Can't calculate cost for empty bio */
+	if (!bio->bi_iter.bi_size)
+		goto out;
+
 	switch (bio_op(bio)) {
 	case REQ_OP_READ:
 		coef_seqio	= ioc->params.lcoefs[LCOEF_RSEQIO];
-- 
2.41.0