On 22/05/25 01:54PM, Jan Kara wrote: > On Wed 25-05-22 13:21:23, Ritesh Harjani wrote: > > On 22/05/25 09:29AM, Ye Bin wrote: > > > We got issue as follows: > > > [home]# mount /dev/sda test > > > EXT4-fs (sda): warning: mounting fs with errors, running e2fsck is recommended > > > [home]# dmesg > > > EXT4-fs (sda): warning: mounting fs with errors, running e2fsck is recommended > > > EXT4-fs (sda): Errors on filesystem, clearing orphan list. > > > EXT4-fs (sda): recovery complete > > > EXT4-fs (sda): mounted filesystem with ordered data mode. Quota mode: none. > > > [home]# debugfs /dev/sda > > > debugfs 1.46.5 (30-Dec-2021) > > > Checksum errors in superblock! Retrying... > > > > > > Reason is ext4_orphan_cleanup will reset ‘s_last_orphan’ but not update > > > super block checksum. > > > To solve above issue, defer update super block checksum after ext4_orphan_cleanup. > > > > I agree with the analysis. However after [1], I think all updates to superblock > > (including checksum computation) should be done within buffer lock. > > (lock_buffer(), unlock_buffer()). > > > > [1]: https://lore.kernel.org/all/20201216101844.22917-4-jack@xxxxxxx/ > > So technically you're right that we should hold buffer lock all the time > from before we modify superblock buffer until we recompute the checksum (so > that we avoid writing superblock with mismatched checksum). To do this we'd > have to put checksum recomputations and superblock buffer locking into > ext4_orphan_cleanup() around setting of es->s_last_orphan (in three places > there AFAICS). A bit tedious but it would actually also fix a (theoretical) > race that someone decides to write out superblock after we set > s_last_orphan but before we set the checksum. Ok. Although (I think) it can still be done at just one place before returning from ext4_orphan_cleanup(). But I agree it is mostly a theoretical race (in fact since this is happening during mount, I am not sure if it is even possible?) and there might not be any value addition in doing so by complicating it too much. > > Overall I'm not convinced this is really necessary so I'd be OK even with > what Ye suggested. That is IMHO better than mostly pointless locking just > around checksum computation because that just makes reader wonder why is it > needed... Sure, yes. Thanks for explaining it. -ritesh > > Honza > > > > > With lock changes added, feel free to add - > > > > Reviewed-by: Ritesh Harjani <ritesh.list@xxxxxxxxx> > > > > > > > > > > > > > Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx> > > > --- > > > fs/ext4/super.c | 16 ++++++++-------- > > > 1 file changed, 8 insertions(+), 8 deletions(-) > > > > > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > > > index f9a3ad683b4a..c47204029429 100644 > > > --- a/fs/ext4/super.c > > > +++ b/fs/ext4/super.c > > > @@ -5300,14 +5300,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) > > > err = percpu_counter_init(&sbi->s_freeinodes_counter, freei, > > > GFP_KERNEL); > > > } > > > - /* > > > - * Update the checksum after updating free space/inode > > > - * counters. Otherwise the superblock can have an incorrect > > > - * checksum in the buffer cache until it is written out and > > > - * e2fsprogs programs trying to open a file system immediately > > > - * after it is mounted can fail. > > > - */ > > > - ext4_superblock_csum_set(sb); > > > if (!err) > > > err = percpu_counter_init(&sbi->s_dirs_counter, > > > ext4_count_dirs(sb), GFP_KERNEL); > > > @@ -5365,6 +5357,14 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) > > > EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS; > > > ext4_orphan_cleanup(sb, es); > > > EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS; > > > + /* > > > + * Update the checksum after updating free space/inode counters and > > > + * ext4_orphan_cleanup. Otherwise the superblock can have an incorrect > > > + * checksum in the buffer cache until it is written out and > > > + * e2fsprogs programs trying to open a file system immediately > > > + * after it is mounted can fail. > > > + */ > > > + ext4_superblock_csum_set(sb); > > > if (needs_recovery) { > > > ext4_msg(sb, KERN_INFO, "recovery complete"); > > > err = ext4_mark_recovery_complete(sb, es); > > > -- > > > 2.31.1 > > > > -- > Jan Kara <jack@xxxxxxxx> > SUSE Labs, CR
