Re: [PATCH v4 3/3] md/raid10: optimize check_decay_read_errors()
From: Song Liu <song@kernel.org>
Date: 2023-05-22 17:43:50
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On Mon, May 22, 2023 at 12:27 AM [off-list ref] wrote:
From: Li Nan <redacted> check_decay_read_errors() is used to handle rdev->read_errors. But read_errors is inc and read after check_decay_read_errors() is invoked in fix_read_error(). Put all operations of read_errors into check_decay_read_errors() and clean up unnecessary atomic_read of read_errors.
If I understand correctly, this patch doesn't change the behavior of the code. If this is the case, I guess we don't really need it. The original code looks reasonable to me. Thanks, Song
quoted hunk ↗ jump to hunk
Suggested-by: Yu Kuai <redacted> Signed-off-by: Li Nan <redacted> --- drivers/md/raid10.c | 41 ++++++++++++++++++++++++----------------- 1 file changed, 24 insertions(+), 17 deletions(-)diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 4fcfcb350d2b..d31eed17f186 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c@@ -2655,23 +2655,24 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio) } /* - * Used by fix_read_error() to decay the per rdev read_errors. + * Used by fix_read_error() to decay the per rdev read_errors and check if + * read_error > max_read_errors. * We halve the read error count for every hour that has elapsed * since the last recorded read error. * */ -static void check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev) +static bool check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev) { - long cur_time_mon; + time64_t cur_time_mon = ktime_get_seconds(); unsigned long hours_since_last; - unsigned int read_errors = atomic_read(&rdev->read_errors); - - cur_time_mon = ktime_get_seconds(); + unsigned int read_errors; + unsigned int max_read_errors = + atomic_read(&mddev->max_corr_read_errors); if (rdev->last_read_error == 0) { /* first time we've seen a read error */ rdev->last_read_error = cur_time_mon; - return; + goto increase; } hours_since_last = (long)(cur_time_mon -@@ -2684,10 +2685,25 @@ static void check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev) * just set read errors to 0. We do this to avoid * overflowing the shift of read_errors by hours_since_last. */ + read_errors = atomic_read(&rdev->read_errors); if (hours_since_last >= 8 * sizeof(read_errors)) atomic_set(&rdev->read_errors, 0); else atomic_set(&rdev->read_errors, read_errors >> hours_since_last); + +increase: + read_errors = atomic_inc_return(&rdev->read_errors); + if (read_errors > max_read_errors) { + pr_notice("md/raid10:%s: %pg: Raid device exceeded read_error threshold [cur %d:max %d]\n", + mdname(mddev), rdev->bdev, + read_errors, max_read_errors); + pr_notice("md/raid10:%s: %pg: Failing raid device\n", + mdname(mddev), rdev->bdev); + md_error(mddev, rdev); + return false; + } + + return true; } static int r10_sync_page_io(struct md_rdev *rdev, sector_t sector,@@ -2727,7 +2743,6 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10 int sect = 0; /* Offset from r10_bio->sector */ int sectors = r10_bio->sectors; struct md_rdev *rdev; - int max_read_errors = atomic_read(&mddev->max_corr_read_errors); int d = r10_bio->devs[r10_bio->read_slot].devnum; /* still own a reference to this rdev, so it cannot@@ -2740,15 +2755,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10 more fix_read_error() attempts */ return; - check_decay_read_errors(mddev, rdev); - atomic_inc(&rdev->read_errors); - if (atomic_read(&rdev->read_errors) > max_read_errors) { - pr_notice("md/raid10:%s: %pg: Raid device exceeded read_error threshold [cur %d:max %d]\n", - mdname(mddev), rdev->bdev, - atomic_read(&rdev->read_errors), max_read_errors); - pr_notice("md/raid10:%s: %pg: Failing raid device\n", - mdname(mddev), rdev->bdev); - md_error(mddev, rdev); + if (!check_decay_read_errors(mddev, rdev)) { r10_bio->devs[r10_bio->read_slot].bio = IO_BLOCKED; return; } --2.31.1