On Fri 14-03-25 13:14:10, Ojaswin Mujoo wrote:
> Presently we always BUG_ON if trying to start a transaction on a journal marked
> with JBD2_UNMOUNT, since this should never happen. However, while ltp running
> stress tests, it was observed that in case of some error handling paths, it is
> possible for update_super_work to start a transaction after the journal is
> destroyed eg:
>
> (umount)
> ext4_kill_sb
> kill_block_super
> generic_shutdown_super
> sync_filesystem /* commits all txns */
> evict_inodes
> /* might start a new txn */
> ext4_put_super
> flush_work(&sbi->s_sb_upd_work) /* flush the workqueue */
> jbd2_journal_destroy
> journal_kill_thread
> journal->j_flags |= JBD2_UNMOUNT;
> jbd2_journal_commit_transaction
> jbd2_journal_get_descriptor_buffer
> jbd2_journal_bmap
> ext4_journal_bmap
> ext4_map_blocks
> ...
> ext4_inode_error
> ext4_handle_error
> schedule_work(&sbi->s_sb_upd_work)
>
> /* work queue kicks in */
> update_super_work
> jbd2_journal_start
> start_this_handle
> BUG_ON(journal->j_flags &
> JBD2_UNMOUNT)
>
> Hence, introduce a new mount flag to indicate journal is destroying and only do
> a journaled (and deferred) update of sb if this flag is not set. Otherwise, just
> fallback to an un-journaled commit.
>
> Further, in the journal destroy path, we have the following sequence:
>
> 1. Set mount flag indicating journal is destroying
> 2. force a commit and wait for it
> 3. flush pending sb updates
>
> This sequence is important as it ensures that, after this point, there is no sb
> update that might be journaled so it is safe to update the sb outside the
> journal. (To avoid race discussed in 2d01ddc86606)
>
> Also, we don't need a similar check in ext4_grp_locked_error since it is only
> called from mballoc and AFAICT it would be always valid to schedule work here.
>
> Fixes: 2d01ddc86606 ("ext4: save error info to sb through journal if available")
> Reported-by: Mahesh Kumar <maheshkumar657g@xxxxxxxxx>
> Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
Mostly looks good. Couple of small comments below:
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1179,6 +1179,7 @@ struct ext4_inode_info {
> #define EXT4_ERROR_FS 0x0002 /* Errors detected */
> #define EXT4_ORPHAN_FS 0x0004 /* Orphans being recovered */
> #define EXT4_FC_REPLAY 0x0020 /* Fast commit replay ongoing */
> +#define EXT4_JOURNAL_DESTORY 0x0040 /* Journal is in process of destroying */
This should be defined as part of the following enum:
/*
* run-time mount flags
*/
enum {
EXT4_MF_MNTDIR_SAMPLED,
EXT4_MF_FC_INELIGIBLE /* Fast commit ineligible */
};
Also you have a typo in the flag name. I guess it should be
EXT4_MF_JOURNAL_DESTROY.
> @@ -4957,8 +4961,6 @@ static int ext4_load_and_init_journal(struct super_block *sb,
> return 0;
>
> out:
> - /* flush s_sb_upd_work before destroying the journal. */
> - flush_work(&sbi->s_sb_upd_work);
> ext4_journal_destroy(sbi, sbi->s_journal);
> return -EINVAL;
> }
> @@ -5648,8 +5650,6 @@ failed_mount8: __maybe_unused
> sbi->s_ea_block_cache = NULL;
>
> if (sbi->s_journal) {
> - /* flush s_sb_upd_work before journal destroy. */
> - flush_work(&sbi->s_sb_upd_work);
> ext4_journal_destroy(sbi, sbi->s_journal);
> }
> failed_mount3a:
These are good. I would also move the flush_work() in ext4_put_super()
into else branch of:
if (sbi->s_journal)
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
