From: Qu Wenruo <wqu@suse.com>
To: linux-btrfs@vger.kernel.org
Subject: [PATCH] btrfs-progs: do not allow setting seed flag on fs with dirty log
Date: Fri, 15 Apr 2022 19:37:43 +0800 [thread overview]
Message-ID: <4022d9f87067124c26bb83d4bba1970c954cdf50.1650022504.git.wqu@suse.com> (raw)
[BUG]
The following sequence operation can lead to a seed fs rejected by
kernel:
# Generate a fs with dirty log
mkfs.btrfs -f $file
mount $dev $mnt
xfs_io -f -c "pwrite 0 16k" -c fsync $mnt/file
cp $file $file.backup
umount $mnt
mv $file.backup $file
# now $file has dirty log, set seed flag on it
btrfstune -S1 $file
# mount will fail
mount $file $mnt
The mount failure with the following dmesg:
[ 980.363667] loop0: detected capacity change from 0 to 262144
[ 980.371177] BTRFS info (device loop0): flagging fs with big metadata feature
[ 980.372229] BTRFS info (device loop0): using free space tree
[ 980.372639] BTRFS info (device loop0): has skinny extents
[ 980.375075] BTRFS info (device loop0): start tree-log replay
[ 980.375513] BTRFS warning (device loop0): log replay required on RO media
[ 980.381652] BTRFS error (device loop0): open_ctree failed
[CAUSE]
Although btrfs will replay its dirty log even with RO mount, but kernel
will treat seed device as RO device, and dirty log can not be replayed
on RO device.
This rejection is already the better end, just imagine if we don't treat
seed device as RO, and replayed the dirty log.
The filesystem relying on the seed device will be completely screwed up.
[FIX]
Just add extra check on log tree in btrfstune to reject setting seed
flag on filesystems with dirty log.
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
btrfstune.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/btrfstune.c b/btrfstune.c
index 33c83bf16291..7e4ad30a1cbd 100644
--- a/btrfstune.c
+++ b/btrfstune.c
@@ -59,6 +59,10 @@ static int update_seeding_flag(struct btrfs_root *root, int set_flag)
device);
return 1;
}
+ if (btrfs_super_log_root(disk_super)) {
+ error("this filesystem has dirty log, can not set seed flag");
+ return 1;
+ }
super_flags |= BTRFS_SUPER_FLAG_SEEDING;
} else {
if (!(super_flags & BTRFS_SUPER_FLAG_SEEDING)) {
--
2.35.1
next reply other threads:[~2022-04-15 11:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-15 11:37 Qu Wenruo [this message]
2022-04-18 6:41 ` [PATCH] btrfs-progs: do not allow setting seed flag on fs with dirty log Nikolay Borisov
2022-04-18 6:44 ` Qu Wenruo
2022-04-18 11:58 ` Nikolay Borisov
2022-04-18 15:30 ` Josef Bacik
2022-04-18 23:31 ` Qu Wenruo
2022-04-19 12:07 ` Anand Jain
2022-04-19 12:10 ` Qu Wenruo
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