From cb3ad87bafde7e4c33fcee8e119c50bb834d5bb6 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Tue, 19 Apr 2022 19:36:21 +0800 Subject: [PATCH] btrfs-progs: do not allow setting seed flag on fs with dirty log [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. Reviewed-by: Josef Bacik Reviewed-by: Nikolay Borisov Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- btrfstune.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/btrfstune.c b/btrfstune.c index 33c83bf1..204b962f 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("filesystem with dirty log detected, not setting seed flag"); + return 1; + } super_flags |= BTRFS_SUPER_FLAG_SEEDING; } else { if (!(super_flags & BTRFS_SUPER_FLAG_SEEDING)) {