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SubjectRe: [f2fs-dev] [PATCH v3] f2fs: add a rw_sem to cover quota flag changes
On 06/18, Chao Yu wrote:
> On 2019/6/14 10:46, Jaegeuk Kim wrote:
> > On 06/11, Chao Yu wrote:
> >> On 2019/6/5 2:36, Jaegeuk Kim wrote:
> >>> Two paths to update quota and f2fs_lock_op:
> >>>
> >>> 1.
> >>> - lock_op
> >>> | - quota_update
> >>> `- unlock_op
> >>>
> >>> 2.
> >>> - quota_update
> >>> - lock_op
> >>> `- unlock_op
> >>>
> >>> But, we need to make a transaction on quota_update + lock_op in #2 case.
> >>> So, this patch introduces:
> >>> 1. lock_op
> >>> 2. down_write
> >>> 3. check __need_flush
> >>> 4. up_write
> >>> 5. if there is dirty quota entries, flush them
> >>> 6. otherwise, good to go
> >>>
> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> >>> ---
> >>>
> >>> v3 from v2:
> >>> - refactor to fix quota corruption issue
> >>> : it seems that the previous scenario is not real and no deadlock case was
> >>> encountered.
> >>
> >> - f2fs_dquot_commit
> >> - down_read(&sbi->quota_sem)
> >> - block_operation
> >> - f2fs_lock_all
> >> - need_flush_quota
> >> - down_write(&sbi->quota_sem)
> >> - f2fs_quota_write
> >> - f2fs_lock_op
> >>
> >> Why can't this happen?
> >>
> >> Once more question, should we hold quota_sem during checkpoint to avoid further
> >> quota update? f2fs_lock_op can do this job as well?
> >
> > I couldn't find write_dquot() call to make this happen, and f2fs_lock_op was not
>
> - f2fs_dquot_commit
> - dquot_commit
> ->commit_dqblk (v2_write_dquot)
> - qtree_write_dquot
> ->quota_write (f2fs_quota_write)
> - f2fs_lock_op
>
> Do you mean there is no such way that calling f2fs_lock_op() from
> f2fs_quota_write()? So that deadlock condition is not existing?

I mean write_dquot->f2fs_dquot_commit and block_operation seems not racing
together.

>
> Thanks,
>
> > enough to cover quota updates. Current stress & power-cut tests are running for
> > several days without problem with this patch.
> >
> >>
> >> Thanks,
> >>
> >>>
> >>> fs/f2fs/checkpoint.c | 41 +++++++++++++++++++----------------------
> >>> fs/f2fs/f2fs.h | 1 +
> >>> fs/f2fs/super.c | 26 +++++++++++++++++++++-----
> >>> 3 files changed, 41 insertions(+), 27 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> >>> index 89825261d474..43f65f0962e5 100644
> >>> --- a/fs/f2fs/checkpoint.c
> >>> +++ b/fs/f2fs/checkpoint.c
> >>> @@ -1131,17 +1131,24 @@ static void __prepare_cp_block(struct f2fs_sb_info *sbi)
> >>>
> >>> static bool __need_flush_quota(struct f2fs_sb_info *sbi)
> >>> {
> >>> + bool ret = false;
> >>> +
> >>> if (!is_journalled_quota(sbi))
> >>> return false;
> >>> - if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH))
> >>> - return false;
> >>> - if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR))
> >>> - return false;
> >>> - if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_FLUSH))
> >>> - return true;
> >>> - if (get_pages(sbi, F2FS_DIRTY_QDATA))
> >>> - return true;
> >>> - return false;
> >>> +
> >>> + down_write(&sbi->quota_sem);
> >>> + if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH)) {
> >>> + ret = false;
> >>> + } else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR)) {
> >>> + ret = false;
> >>> + } else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_FLUSH)) {
> >>> + clear_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
> >>> + ret = true;
> >>> + } else if (get_pages(sbi, F2FS_DIRTY_QDATA)) {
> >>> + ret = true;
> >>> + }
> >>> + up_write(&sbi->quota_sem);
> >>> + return ret;
> >>> }
> >>>
> >>> /*
> >>> @@ -1160,26 +1167,22 @@ static int block_operations(struct f2fs_sb_info *sbi)
> >>> blk_start_plug(&plug);
> >>>
> >>> retry_flush_quotas:
> >>> + f2fs_lock_all(sbi);
> >>> if (__need_flush_quota(sbi)) {
> >>> int locked;
> >>>
> >>> if (++cnt > DEFAULT_RETRY_QUOTA_FLUSH_COUNT) {
> >>> set_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH);
> >>> - f2fs_lock_all(sbi);
> >>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
> >>> goto retry_flush_dents;
> >>> }
> >>> - clear_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
> >>> + f2fs_unlock_all(sbi);
> >>>
> >>> /* only failed during mount/umount/freeze/quotactl */
> >>> locked = down_read_trylock(&sbi->sb->s_umount);
> >>> f2fs_quota_sync(sbi->sb, -1);
> >>> if (locked)
> >>> up_read(&sbi->sb->s_umount);
> >>> - }
> >>> -
> >>> - f2fs_lock_all(sbi);
> >>> - if (__need_flush_quota(sbi)) {
> >>> - f2fs_unlock_all(sbi);
> >>> cond_resched();
> >>> goto retry_flush_quotas;
> >>> }
> >>> @@ -1201,12 +1204,6 @@ static int block_operations(struct f2fs_sb_info *sbi)
> >>> */
> >>> down_write(&sbi->node_change);
> >>>
> >>> - if (__need_flush_quota(sbi)) {
> >>> - up_write(&sbi->node_change);
> >>> - f2fs_unlock_all(sbi);
> >>> - goto retry_flush_quotas;
> >>> - }
> >>> -
> >>> if (get_pages(sbi, F2FS_DIRTY_IMETA)) {
> >>> up_write(&sbi->node_change);
> >>> f2fs_unlock_all(sbi);
> >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >>> index 9674a85154b2..9bd2bf0f559b 100644
> >>> --- a/fs/f2fs/f2fs.h
> >>> +++ b/fs/f2fs/f2fs.h
> >>> @@ -1253,6 +1253,7 @@ struct f2fs_sb_info {
> >>> block_t unusable_block_count; /* # of blocks saved by last cp */
> >>>
> >>> unsigned int nquota_files; /* # of quota sysfile */
> >>> + struct rw_semaphore quota_sem; /* blocking cp for flags */
> >>>
> >>> /* # of pages, see count_type */
> >>> atomic_t nr_pages[NR_COUNT_TYPE];
> >>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> >>> index 15d7e30bfc72..5a318399a2fa 100644
> >>> --- a/fs/f2fs/super.c
> >>> +++ b/fs/f2fs/super.c
> >>> @@ -1964,6 +1964,7 @@ int f2fs_quota_sync(struct super_block *sb, int type)
> >>> int cnt;
> >>> int ret;
> >>>
> >>> + down_read(&sbi->quota_sem);
> >>> ret = dquot_writeback_dquots(sb, type);
> >>> if (ret)
> >>> goto out;
> >>> @@ -2001,6 +2002,7 @@ int f2fs_quota_sync(struct super_block *sb, int type)
> >>> out:
> >>> if (ret)
> >>> set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
> >>> + up_read(&sbi->quota_sem);
> >>> return ret;
> >>> }
> >>>
> >>> @@ -2094,32 +2096,40 @@ static void f2fs_truncate_quota_inode_pages(struct super_block *sb)
> >>>
> >>> static int f2fs_dquot_commit(struct dquot *dquot)
> >>> {
> >>> + struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
> >>> int ret;
> >>>
> >>> + down_read(&sbi->quota_sem);
> >>> ret = dquot_commit(dquot);
> >>> if (ret < 0)
> >>> - set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
> >>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
> >>> + up_read(&sbi->quota_sem);
> >>> return ret;
> >>> }
> >>>
> >>> static int f2fs_dquot_acquire(struct dquot *dquot)
> >>> {
> >>> + struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
> >>> int ret;
> >>>
> >>> + down_read(&sbi->quota_sem);
> >>> ret = dquot_acquire(dquot);
> >>> if (ret < 0)
> >>> - set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
> >>> -
> >>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
> >>> + up_read(&sbi->quota_sem);
> >>> return ret;
> >>> }
> >>>
> >>> static int f2fs_dquot_release(struct dquot *dquot)
> >>> {
> >>> + struct f2fs_sb_info *sbi = F2FS_SB(dquot->dq_sb);
> >>> int ret;
> >>>
> >>> + down_read(&sbi->quota_sem);
> >>> ret = dquot_release(dquot);
> >>> if (ret < 0)
> >>> - set_sbi_flag(F2FS_SB(dquot->dq_sb), SBI_QUOTA_NEED_REPAIR);
> >>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
> >>> + up_read(&sbi->quota_sem);
> >>> return ret;
> >>> }
> >>>
> >>> @@ -2129,22 +2139,27 @@ static int f2fs_dquot_mark_dquot_dirty(struct dquot *dquot)
> >>> struct f2fs_sb_info *sbi = F2FS_SB(sb);
> >>> int ret;
> >>>
> >>> + down_read(&sbi->quota_sem);
> >>> ret = dquot_mark_dquot_dirty(dquot);
> >>>
> >>> /* if we are using journalled quota */
> >>> if (is_journalled_quota(sbi))
> >>> set_sbi_flag(sbi, SBI_QUOTA_NEED_FLUSH);
> >>>
> >>> + up_read(&sbi->quota_sem);
> >>> return ret;
> >>> }
> >>>
> >>> static int f2fs_dquot_commit_info(struct super_block *sb, int type)
> >>> {
> >>> + struct f2fs_sb_info *sbi = F2FS_SB(sb);
> >>> int ret;
> >>>
> >>> + down_read(&sbi->quota_sem);
> >>> ret = dquot_commit_info(sb, type);
> >>> if (ret < 0)
> >>> - set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
> >>> + set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
> >>> + up_read(&sbi->quota_sem);
> >>> return ret;
> >>> }
> >>>
> >>> @@ -3253,6 +3268,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
> >>> }
> >>>
> >>> init_rwsem(&sbi->cp_rwsem);
> >>> + init_rwsem(&sbi->quota_sem);
> >>> init_waitqueue_head(&sbi->cp_wait);
> >>> init_sb_info(sbi);
> >>>
> >>>
> > .
> >

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