From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Date: Wed, 26 Feb 2014 17:49:31 +0100 Subject: [Ocfs2-devel] [PATCH 4/6] ocfs2: Implement delayed dropping of last dquot reference In-Reply-To: <1393433373-28767-1-git-send-email-jack@suse.cz> References: <1393433373-28767-1-git-send-email-jack@suse.cz> Message-ID: <1393433373-28767-5-git-send-email-jack@suse.cz> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com We cannot drop last dquot reference from downconvert thread as that creates the following deadlock: NODE 1 NODE2 holds dentry lock for 'foo' holds inode lock for GLOBAL_BITMAP_SYSTEM_INODE dquot_initialize(bar) ocfs2_dquot_acquire() ocfs2_inode_lock(USER_QUOTA_SYSTEM_INODE) ... downconvert thread (triggered from another node or a different process from NODE2) ocfs2_dentry_post_unlock() ... iput(foo) ocfs2_evict_inode(foo) ocfs2_clear_inode(foo) dquot_drop(inode) ... ocfs2_dquot_release() ocfs2_inode_lock(USER_QUOTA_SYSTEM_INODE) - blocks finds we need more space in quota file ... ocfs2_extend_no_holes() ocfs2_inode_lock(GLOBAL_BITMAP_SYSTEM_INODE) - deadlocks waiting for downconvert thread We solve the problem by postponing dropping of the last dquot reference to a workqueue if it happens from the downconvert thread. Reviewed-by: Mark Fasheh Reviewed-by: Srinivas Eeda Signed-off-by: Jan Kara --- fs/ocfs2/ocfs2.h | 5 +++++ fs/ocfs2/quota.h | 2 ++ fs/ocfs2/quota_global.c | 35 +++++++++++++++++++++++++++++++++++ fs/ocfs2/super.c | 8 ++++++++ 4 files changed, 50 insertions(+) diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h index 553f53cc73ae..64c02239ba46 100644 --- a/fs/ocfs2/ocfs2.h +++ b/fs/ocfs2/ocfs2.h @@ -30,6 +30,7 @@ #include #include #include +#include #include #include #include @@ -419,6 +420,10 @@ struct ocfs2_super struct ocfs2_dentry_lock *dentry_lock_list; struct work_struct dentry_lock_work; + /* List of dquot structures to drop last reference to */ + struct llist_head dquot_drop_list; + struct work_struct dquot_drop_work; + wait_queue_head_t osb_mount_event; /* Truncate log info */ diff --git a/fs/ocfs2/quota.h b/fs/ocfs2/quota.h index d5ab56cbe5c5..f266d67df3c6 100644 --- a/fs/ocfs2/quota.h +++ b/fs/ocfs2/quota.h @@ -28,6 +28,7 @@ struct ocfs2_dquot { unsigned int dq_use_count; /* Number of nodes having reference to this entry in global quota file */ s64 dq_origspace; /* Last globally synced space usage */ s64 dq_originodes; /* Last globally synced inode usage */ + struct llist_node list; /* Member of list of dquots to drop */ }; /* Description of one chunk to recover in memory */ @@ -110,6 +111,7 @@ int ocfs2_read_quota_phys_block(struct inode *inode, u64 p_block, int ocfs2_create_local_dquot(struct dquot *dquot); int ocfs2_local_release_dquot(handle_t *handle, struct dquot *dquot); int ocfs2_local_write_dquot(struct dquot *dquot); +void ocfs2_drop_dquot_refs(struct work_struct *work); extern const struct dquot_operations ocfs2_quota_operations; extern struct quota_format_type ocfs2_quota_format; diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c index aaa50611ec66..7921e209c64b 100644 --- a/fs/ocfs2/quota_global.c +++ b/fs/ocfs2/quota_global.c @@ -10,6 +10,7 @@ #include #include #include +#include #include @@ -679,6 +680,27 @@ static int ocfs2_calc_qdel_credits(struct super_block *sb, int type) OCFS2_INODE_UPDATE_CREDITS; } +void ocfs2_drop_dquot_refs(struct work_struct *work) +{ + struct ocfs2_super *osb = container_of(work, struct ocfs2_super, + dquot_drop_work); + struct llist_node *list; + struct ocfs2_dquot *odquot, *next_odquot; + + list = llist_del_all(&osb->dquot_drop_list); + llist_for_each_entry_safe(odquot, next_odquot, list, list) { + /* Drop the reference we acquired in ocfs2_dquot_release() */ + dqput(&odquot->dq_dquot); + } +} + +/* + * Called when the last reference to dquot is dropped. If we are called from + * downconvert thread, we cannot do all the handling here because grabbing + * quota lock could deadlock (the node holding the quota lock could need some + * other cluster lock to proceed but with blocked downconvert thread we cannot + * release any lock). + */ static int ocfs2_release_dquot(struct dquot *dquot) { handle_t *handle; @@ -694,6 +716,19 @@ static int ocfs2_release_dquot(struct dquot *dquot) /* Check whether we are not racing with some other dqget() */ if (atomic_read(&dquot->dq_count) > 1) goto out; + /* Running from downconvert thread? Postpone quota processing to wq */ + if (current == osb->dc_task) { + /* + * Grab our own reference to dquot and queue it for delayed + * dropping. Quota code rechecks after calling + * ->release_dquot() and won't free dquot structure. + */ + dqgrab(dquot); + /* First entry on list -> queue work */ + if (llist_add(&OCFS2_DQUOT(dquot)->list, &osb->dquot_drop_list)) + queue_work(ocfs2_wq, &osb->dquot_drop_work); + goto out; + } status = ocfs2_lock_global_qf(oinfo, 1); if (status < 0) goto out; diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c index 49d84f80f36c..0a8972deae2b 100644 --- a/fs/ocfs2/super.c +++ b/fs/ocfs2/super.c @@ -1943,6 +1943,11 @@ static void ocfs2_dismount_volume(struct super_block *sb, int mnt_err) ocfs2_disable_quotas(osb); + /* All dquots should be freed by now */ + WARN_ON(!llist_empty(&osb->dquot_drop_list)); + /* Wait for worker to be done with the work structure in osb */ + cancel_work_sync(&osb->dquot_drop_work); + ocfs2_shutdown_local_alloc(osb); /* This will disable recovery and flush any recovery work. */ @@ -2279,6 +2284,9 @@ static int ocfs2_initialize_super(struct super_block *sb, INIT_WORK(&osb->dentry_lock_work, ocfs2_drop_dl_inodes); osb->dentry_lock_list = NULL; + INIT_WORK(&osb->dquot_drop_work, ocfs2_drop_dquot_refs); + init_llist_head(&osb->dquot_drop_list); + /* get some pseudo constants for clustersize bits */ osb->s_clustersize_bits = le32_to_cpu(di->id2.i_super.s_clustersize_bits); -- 1.8.1.4