On Thu 31-10-19 19:00:33, Jan Kara wrote:
> On Thu 31-10-19 10:39:20, Dmitry Monakhov wrote:
> > From: Dmitry Monakhov <dmtrmonakhov@xxxxxxxxxxxxxx>
> >
> > There is a race window where quota was redirted once we drop dq_list_lock inside dqput(),
> > but before we grab dquot->dq_lock inside dquot_release()
> >
> > TASK1 TASK2 (chowner)
> > ->dqput()
> > we_slept:
> > spin_lock(&dq_list_lock)
> > if (dquot_dirty(dquot)) {
> > spin_unlock(&dq_list_lock);
> > dquot->dq_sb->dq_op->write_dquot(dquot);
> > goto we_slept
> > if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
> > spin_unlock(&dq_list_lock);
> > dquot->dq_sb->dq_op->release_dquot(dquot);
> > dqget()
> > mark_dquot_dirty()
> > dqput()
> > goto we_slept;
> > }
> > So dquot dirty quota will be released by TASK1, but on next we_sleept loop
> > we detect this and call ->write_dquot() for it.
> > XFSTEST: https://github.com/dmonakhov/xfstests/commit/440a80d4cbb39e9234df4d7240aee1d551c36107
>
> Yeah, good catch. Both patches look good to me. I've added them to my tree.
And forgot to add: Thanks for both patches and also the regression tests! I
really appreciate it!
Honza
> > Signed-off-by: Dmitry Monakhov <dmtrmonakhov@xxxxxxxxxxxxxx>
> > ---
> > fs/ocfs2/quota_global.c | 2 +-
> > fs/quota/dquot.c | 2 +-
> > include/linux/quotaops.h | 10 ++++++++++
> > 3 files changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c
> > index 7a92219..eda8348 100644
> > --- a/fs/ocfs2/quota_global.c
> > +++ b/fs/ocfs2/quota_global.c
> > @@ -728,7 +728,7 @@ static int ocfs2_release_dquot(struct dquot *dquot)
> >
> > mutex_lock(&dquot->dq_lock);
> > /* Check whether we are not racing with some other dqget() */
> > - if (atomic_read(&dquot->dq_count) > 1)
> > + if (dquot_is_busy(dquot))
> > goto out;
> > /* Running from downconvert thread? Postpone quota processing to wq */
> > if (current == osb->dc_task) {
> > diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> > index b492b9e..72d24a5 100644
> > --- a/fs/quota/dquot.c
> > +++ b/fs/quota/dquot.c
> > @@ -497,7 +497,7 @@ int dquot_release(struct dquot *dquot)
> >
> > mutex_lock(&dquot->dq_lock);
> > /* Check whether we are not racing with some other dqget() */
> > - if (atomic_read(&dquot->dq_count) > 1)
> > + if (dquot_is_busy(dquot))
> > goto out_dqlock;
> > if (dqopt->ops[dquot->dq_id.type]->release_dqblk) {
> > ret = dqopt->ops[dquot->dq_id.type]->release_dqblk(dquot);
> > diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
> > index 185d948..91e0b76 100644
> > --- a/include/linux/quotaops.h
> > +++ b/include/linux/quotaops.h
> > @@ -54,6 +54,16 @@ static inline struct dquot *dqgrab(struct dquot *dquot)
> > atomic_inc(&dquot->dq_count);
> > return dquot;
> > }
> > +
> > +static inline bool dquot_is_busy(struct dquot *dquot)
> > +{
> > + if (test_bit(DQ_MOD_B, &dquot->dq_flags))
> > + return true;
> > + if (atomic_read(&dquot->dq_count) > 1)
> > + return true;
> > + return false;
> > +}
> > +
> > void dqput(struct dquot *dquot);
> > int dquot_scan_active(struct super_block *sb,
> > int (*fn)(struct dquot *dquot, unsigned long priv),
> > --
> > 2.7.4
> >
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
