58 lines
2.0 KiB
Diff
58 lines
2.0 KiB
Diff
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From f7a6246bab1541d7208a5f0f9f0c6cac114e38da Mon Sep 17 00:00:00 2001
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From: Zhao Heming <heming.zhao@suse.com>
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Date: Wed, 3 Feb 2021 08:22:51 +0800
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Subject: [PATCH 2/2] super1.c: avoid useless sync when bitmap switches from
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clustered to none
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With kernel commit 480523feae58 ("md: only call set_in_sync() when it
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is expected to succeed."), mddev->in_sync in clustered array is always
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zero. It makes metadata resync_offset to always zero.
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When assembling a clusterd array with "-U no-bitmap" option, kernel
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md layer "mddev->resync_offset == 0" and "mddev->bitmap == NULL" will
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trigger raid1 do sync on every bitmap chunk. the sync action is useless,
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we should avoid it.
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Related kernel flow:
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```
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md_do_sync
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mddev->pers->sync_request
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raid1_sync_request
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md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1)
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__bitmap_start_sync(bitmap, offset,&blocks1, degraded)
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if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
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*blocks = 1024;
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return 1; /* always resync if no bitmap */
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}
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```
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Reprodusible steps:
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```
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node1 # mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sd{a,b}
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node1 # mdadm -Ss
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(in another shell, executing & watching: watch -n 1 'cat /proc/mdstat')
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node1 # mdadm -A -U no-bitmap /dev/md0 /dev/sd{a,b}
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```
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Signed-off-by: Zhao Heming <heming.zhao@suse.com>
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Signed-off-by: Jes Sorensen <jsorensen@fb.com>
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---
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super1.c | 2 ++
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1 file changed, 2 insertions(+)
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diff --git a/super1.c b/super1.c
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index 70aa1d3d0219..7b03329dac91 100644
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--- a/super1.c
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+++ b/super1.c
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@@ -1346,6 +1346,8 @@ static int update_super1(struct supertype *st, struct mdinfo *info,
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memcpy(bms->uuid, sb->set_uuid, 16);
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} else if (strcmp(update, "no-bitmap") == 0) {
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sb->feature_map &= ~__cpu_to_le32(MD_FEATURE_BITMAP_OFFSET);
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+ if (bms->version == BITMAP_MAJOR_CLUSTERED && !IsBitmapDirty(devname))
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+ sb->resync_offset = MaxSector;
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} else if (strcmp(update, "bbl") == 0) {
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/* only possible if there is room after the bitmap, or if
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* there is no bitmap
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--
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1.8.3.1
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