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Wed, 28 Feb 2024 19:49:33 +0800 (CST) From: Yu Kuai To: xni@redhat.com, paul.e.luse@linux.intel.com, song@kernel.org, shli@fb.com, neilb@suse.com Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: [PATCH md-6.9 v3 04/11] md/raid1: fix choose next idle in read_balance() Date: Wed, 28 Feb 2024 19:43:26 +0800 Message-Id: <20240228114333.527222-5-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240228114333.527222-1-yukuai1@huaweicloud.com> References: <20240228114333.527222-1-yukuai1@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: cCh0CgAn9g7IHd9l+eamFQ--.6969S8 X-Coremail-Antispam: 1UD129KBjvJXoWxXryrKr1kKr4fAFyUJry3twb_yoWrXw1xpw 4jvwsaqrWUXF43u3sxJw4UurySg345JayrGrZ7C34Fgry3XrWqqa47K342vry8CFs3J342 qw18GrZru3WkKa7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPF14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr 1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s0D M2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjx v20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1l F7xvr2IYc2Ij64vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7M4IIrI8v6xkF7I0E8cxan2 IY04v7MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAF wI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc4 0Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AK xVWxJVW8Jr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r 4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr1j6F4UJbIYCTnIWIevJa73UjIFyTuYvjfUOBTY UUUUU X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1792143719651323375 X-GMAIL-MSGID: 1792143719651323375 From: Yu Kuai Commit 12cee5a8a29e ("md/raid1: prevent merging too large request") add the case choose next idle in read_balance(): read_balance: for_each_rdev if(next_seq_sect == this_sector || dist == 0) -> sequential reads best_disk = disk; if (...) choose_next_idle = 1 continue; for_each_rdev -> iterate next rdev if (pending == 0) best_disk = disk; -> choose the next idle disk break; if (choose_next_idle) -> keep using this rdev if there are no other idle disk contine However, commit 2e52d449bcec ("md/raid1: add failfast handling for reads.") remove the code: - /* If device is idle, use it */ - if (pending == 0) { - best_disk = disk; - break; - } Hence choose next idle will never work now, fix this problem by following: 1) don't set best_disk in this case, read_balance() will choose the best disk after iterating all the disks; 2) add 'pending' so that other idle disk will be chosen; 3) add a new local variable 'sequential_disk' to record the disk, and if there is no other idle disk, 'sequential_disk' will be chosen; Fixes: 2e52d449bcec ("md/raid1: add failfast handling for reads.") Co-developed-by: Paul Luse Signed-off-by: Paul Luse Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni --- drivers/md/raid1.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 032a6a6c3730..97db9add27df 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -598,13 +598,12 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect const sector_t this_sector = r1_bio->sector; int sectors; int best_good_sectors; - int best_disk, best_dist_disk, best_pending_disk; + int best_disk, best_dist_disk, best_pending_disk, sequential_disk; int disk; sector_t best_dist; unsigned int min_pending; struct md_rdev *rdev; int choose_first; - int choose_next_idle; /* * Check if we can balance. We can balance on the whole @@ -615,11 +614,11 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect sectors = r1_bio->sectors; best_disk = -1; best_dist_disk = -1; + sequential_disk = -1; best_dist = MaxSector; best_pending_disk = -1; min_pending = UINT_MAX; best_good_sectors = 0; - choose_next_idle = 0; clear_bit(R1BIO_FailFast, &r1_bio->state); if ((conf->mddev->recovery_cp < this_sector + sectors) || @@ -712,7 +711,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect int opt_iosize = bdev_io_opt(rdev->bdev) >> 9; struct raid1_info *mirror = &conf->mirrors[disk]; - best_disk = disk; /* * If buffered sequential IO size exceeds optimal * iosize, check if there is idle disk. If yes, choose @@ -731,15 +729,22 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect mirror->next_seq_sect > opt_iosize && mirror->next_seq_sect - opt_iosize >= mirror->seq_start) { - choose_next_idle = 1; - continue; + /* + * Add 'pending' to avoid choosing this disk if + * there is other idle disk. + */ + pending++; + /* + * If there is no other idle disk, this disk + * will be chosen. + */ + sequential_disk = disk; + } else { + best_disk = disk; + break; } - break; } - if (choose_next_idle) - continue; - if (min_pending > pending) { min_pending = pending; best_pending_disk = disk; @@ -751,6 +756,13 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect } } + /* + * sequential IO size exceeds optimal iosize, however, there is no other + * idle disk, so choose the sequential disk. + */ + if (best_disk == -1 && min_pending != 0) + best_disk = sequential_disk; + /* * If all disks are rotational, choose the closest disk. If any disk is * non-rotational, choose the disk with less pending request even the