This is a note to let you know that I've just added the patch titled
btrfs: delete unused BGs while reclaiming BGs
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-delete-unused-bgs-while-reclaiming-bgs.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3ed01616bad6c7e3de196676b542ae3df8058592 Mon Sep 17 00:00:00 2001
From: Naohiro Aota <naota@xxxxxxxxx>
Date: Tue, 6 Jun 2023 14:36:33 +0900
Subject: btrfs: delete unused BGs while reclaiming BGs
From: Naohiro Aota <naota@xxxxxxxxx>
commit 3ed01616bad6c7e3de196676b542ae3df8058592 upstream.
The reclaiming process only starts after the filesystem volumes are
allocated to a certain level (75% by default). Thus, the list of
reclaiming target block groups can build up so huge at the time the
reclaim process kicks in. On a test run, there were over 1000 BGs in the
reclaim list.
As the reclaim involves rewriting the data, it takes really long time to
reclaim the BGs. While the reclaim is running, btrfs_delete_unused_bgs()
won't proceed because the reclaim side is holding
fs_info->reclaim_bgs_lock. As a result, we will have a large number of
unused BGs kept in the unused list. On my test run, I got 1057 unused BGs.
Since deleting a block group is relatively easy and fast work, we can call
btrfs_delete_unused_bgs() while it reclaims BGs, to avoid building up
unused BGs.
Fixes: 18bb8bbf13c1 ("btrfs: zoned: automatically reclaim zones")
CC: stable@xxxxxxxxxxxxxxx # 5.15+
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/block-group.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1636,10 +1636,24 @@ void btrfs_reclaim_bgs_work(struct work_
next:
btrfs_put_block_group(bg);
+
+ mutex_unlock(&fs_info->reclaim_bgs_lock);
+ /*
+ * Reclaiming all the block groups in the list can take really
+ * long. Prioritize cleaning up unused block groups.
+ */
+ btrfs_delete_unused_bgs(fs_info);
+ /*
+ * If we are interrupted by a balance, we can just bail out. The
+ * cleaner thread restart again if necessary.
+ */
+ if (!mutex_trylock(&fs_info->reclaim_bgs_lock))
+ goto end;
spin_lock(&fs_info->unused_bgs_lock);
}
spin_unlock(&fs_info->unused_bgs_lock);
mutex_unlock(&fs_info->reclaim_bgs_lock);
+end:
btrfs_exclop_finish(fs_info);
sb_end_write(fs_info->sb);
}
Patches currently in stable-queue which might be from naota@xxxxxxxxx are
queue-6.1/btrfs-bail-out-reclaim-process-if-filesystem-is-read-only.patch
queue-6.1/btrfs-move-out-now-unused-bg-from-the-reclaim-list.patch
queue-6.1/btrfs-delete-unused-bgs-while-reclaiming-bgs.patch
queue-6.1/btrfs-reinsert-bgs-failed-to-reclaim.patch
