resend: [PATCH v2 mdadm] super1.c: avoid useless sync when bitmap switches from clustered to none
From: "heming.zhao@suse.com" <heming.zhao@suse.com>
Date: 2021-03-03 01:20:02
Subsystem:
the rest · Maintainer:
Linus Torvalds
With kernel commit 480523feae58 ("md: only call set_in_sync() when it
is expected to succeed."), mddev->in_sync in clustered array is always
zero. It makes metadata resync_offset to always zero.
When assembling a clusterd array with "-U no-bitmap" option, kernel
md layer "mddev->resync_offset == 0" and "mddev->bitmap == NULL" will
trigger raid1 do sync on every bitmap chunk. the sync action is useless,
it wastes user a lot of time, we should avoid it.
Related kernel flow:md_do_sync
mddev->pers->sync_request
raid1_sync_request
md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1)
__bitmap_start_sync(bitmap, offset,&blocks1, degraded)
if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
*blocks = 1024;
return 1; /* always resync if no bitmap */
}
Reprodusible steps:
node1 # mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sd{a,b}
node1 # mdadm -Ss
(in another shell, executing & watching: watch -n 1 'cat /proc/mdstat')
node1 # mdadm -A -U no-bitmap /dev/md0 /dev/sd{a,b}
Signed-off-by: Zhao Heming <heming.zhao@suse.com> --- v2: only set MaxSector on bitmap clean device --- super1.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/super1.c b/super1.c
index 19fe6f5..9470025 100644
--- a/super1.c
+++ b/super1.c@@ -1318,6 +1318,8 @@ static int update_super1(struct supertype *st, struct mdinfo *info, memcpy(bms->uuid, sb->set_uuid, 16); } else if (strcmp(update, "no-bitmap") == 0) { sb->feature_map &= ~__cpu_to_le32(MD_FEATURE_BITMAP_OFFSET); + if (bms->version == BITMAP_MAJOR_CLUSTERED && !IsBitmapDirty(devname)) + sb->resync_offset = MaxSector; } else if (strcmp(update, "bbl") == 0) { /* only possible if there is room after the bitmap, or if * there is no bitmap
--
2.30.0