This is a note to let you know that I've just added the patch titled
btrfs: call btrfs_check_rw_degradable only if there is a missing device
to the 5.4-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-call-btrfs_check_rw_degradable-only-if-there-is-a-missing-device.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5c78a5e7aa835c4f08a7c90fe02d19f95a776f29 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@xxxxxxxxxx>
Date: Tue, 19 Oct 2021 18:43:38 +0800
Subject: btrfs: call btrfs_check_rw_degradable only if there is a missing device
From: Anand Jain <anand.jain@xxxxxxxxxx>
commit 5c78a5e7aa835c4f08a7c90fe02d19f95a776f29 upstream.
In open_ctree() in btrfs_check_rw_degradable() [1], we check each block
group individually if at least the minimum number of devices is available
for that profile. If all the devices are available, then we don't have to
check degradable.
[1]
open_ctree()
::
3559 if (!sb_rdonly(sb) && !btrfs_check_rw_degradable(fs_info, NULL)) {
Also before calling btrfs_check_rw_degradable() in open_ctee() at the
line number shown below [2] we call btrfs_read_chunk_tree() and down to
add_missing_dev() to record number of missing devices.
[2]
open_ctree()
::
3454 ret = btrfs_read_chunk_tree(fs_info);
btrfs_read_chunk_tree()
read_one_chunk() / read_one_dev()
add_missing_dev()
So, check if there is any missing device before btrfs_check_rw_degradable()
in open_ctree().
Also, with this the mount command could save ~16ms.[3] in the most
common case, that is no device is missing.
[3]
1) * 16934.96 us | btrfs_check_rw_degradable [btrfs]();
CC: stable@xxxxxxxxxxxxxxx # 4.19+
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/disk-io.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3145,7 +3145,8 @@ retry_root_backup:
goto fail_sysfs;
}
- if (!sb_rdonly(sb) && !btrfs_check_rw_degradable(fs_info, NULL)) {
+ if (!sb_rdonly(sb) && fs_info->fs_devices->missing_devices &&
+ !btrfs_check_rw_degradable(fs_info, NULL)) {
btrfs_warn(fs_info,
"writable mount is not allowed due to too many missing devices");
goto fail_sysfs;
Patches currently in stable-queue which might be from anand.jain@xxxxxxxxxx are
queue-5.4/btrfs-call-btrfs_check_rw_degradable-only-if-there-is-a-missing-device.patch
