3.16.82-rc1 review patch. If anyone has any objections, please let me know.
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From: Dmitry Monakhov dmtrmonakhov@yandex-team.ru
commit df4bb5d128e2c44848aeb36b7ceceba3ac85080d upstream.
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/440a80d4cbb39e9234df4d7240aee1d...
Link: https://lore.kernel.org/r/20191031103920.3919-2-dmonakhov@openvz.org Signed-off-by: Dmitry Monakhov dmtrmonakhov@yandex-team.ru Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Ben Hutchings ben@decadent.org.uk --- fs/ocfs2/quota_global.c | 2 +- fs/quota/dquot.c | 2 +- include/linux/quotaops.h | 10 ++++++++++ 3 files changed, 12 insertions(+), 2 deletions(-)
--- a/fs/ocfs2/quota_global.c +++ b/fs/ocfs2/quota_global.c @@ -714,7 +714,7 @@ static int ocfs2_release_dquot(struct dq
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) { --- a/fs/quota/dquot.c +++ b/fs/quota/dquot.c @@ -475,7 +475,7 @@ 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; mutex_lock(&dqopt->dqio_mutex); if (dqopt->ops[dquot->dq_id.type]->release_dqblk) { --- a/include/linux/quotaops.h +++ b/include/linux/quotaops.h @@ -54,6 +54,16 @@ static inline struct dquot *dqgrab(struc 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),