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ocfs2: implement delayed dropping of last dquot reference
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. Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Mark Fasheh <mfasheh@suse.de> Reviewed-by: Srinivas Eeda <srinivas.eeda@oracle.com> Cc: Joel Becker <jlbec@evilplan.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -30,6 +30,7 @@
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#include <linux/sched.h>
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#include <linux/wait.h>
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#include <linux/list.h>
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#include <linux/llist.h>
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#include <linux/rbtree.h>
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#include <linux/workqueue.h>
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#include <linux/kref.h>
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@ -419,6 +420,10 @@ struct ocfs2_super
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struct ocfs2_dentry_lock *dentry_lock_list;
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struct work_struct dentry_lock_work;
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/* List of dquot structures to drop last reference to */
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struct llist_head dquot_drop_list;
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struct work_struct dquot_drop_work;
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wait_queue_head_t osb_mount_event;
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/* Truncate log info */
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@ -28,6 +28,7 @@ struct ocfs2_dquot {
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unsigned int dq_use_count; /* Number of nodes having reference to this entry in global quota file */
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s64 dq_origspace; /* Last globally synced space usage */
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s64 dq_originodes; /* Last globally synced inode usage */
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struct llist_node list; /* Member of list of dquots to drop */
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};
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/* Description of one chunk to recover in memory */
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@ -110,6 +111,7 @@ int ocfs2_read_quota_phys_block(struct inode *inode, u64 p_block,
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int ocfs2_create_local_dquot(struct dquot *dquot);
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int ocfs2_local_release_dquot(handle_t *handle, struct dquot *dquot);
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int ocfs2_local_write_dquot(struct dquot *dquot);
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void ocfs2_drop_dquot_refs(struct work_struct *work);
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extern const struct dquot_operations ocfs2_quota_operations;
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extern struct quota_format_type ocfs2_quota_format;
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@ -10,6 +10,7 @@
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#include <linux/jiffies.h>
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#include <linux/writeback.h>
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#include <linux/workqueue.h>
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#include <linux/llist.h>
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#include <cluster/masklog.h>
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@ -679,6 +680,27 @@ static int ocfs2_calc_qdel_credits(struct super_block *sb, int type)
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OCFS2_INODE_UPDATE_CREDITS;
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}
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void ocfs2_drop_dquot_refs(struct work_struct *work)
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{
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struct ocfs2_super *osb = container_of(work, struct ocfs2_super,
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dquot_drop_work);
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struct llist_node *list;
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struct ocfs2_dquot *odquot, *next_odquot;
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list = llist_del_all(&osb->dquot_drop_list);
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llist_for_each_entry_safe(odquot, next_odquot, list, list) {
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/* Drop the reference we acquired in ocfs2_dquot_release() */
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dqput(&odquot->dq_dquot);
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}
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}
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/*
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* Called when the last reference to dquot is dropped. If we are called from
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* downconvert thread, we cannot do all the handling here because grabbing
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* quota lock could deadlock (the node holding the quota lock could need some
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* other cluster lock to proceed but with blocked downconvert thread we cannot
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* release any lock).
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*/
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static int ocfs2_release_dquot(struct dquot *dquot)
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{
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handle_t *handle;
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@ -694,6 +716,19 @@ static int ocfs2_release_dquot(struct dquot *dquot)
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/* Check whether we are not racing with some other dqget() */
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if (atomic_read(&dquot->dq_count) > 1)
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goto out;
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/* Running from downconvert thread? Postpone quota processing to wq */
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if (current == osb->dc_task) {
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/*
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* Grab our own reference to dquot and queue it for delayed
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* dropping. Quota code rechecks after calling
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* ->release_dquot() and won't free dquot structure.
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*/
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dqgrab(dquot);
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/* First entry on list -> queue work */
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if (llist_add(&OCFS2_DQUOT(dquot)->list, &osb->dquot_drop_list))
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queue_work(ocfs2_wq, &osb->dquot_drop_work);
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goto out;
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}
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status = ocfs2_lock_global_qf(oinfo, 1);
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if (status < 0)
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goto out;
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@ -1941,6 +1941,11 @@ static void ocfs2_dismount_volume(struct super_block *sb, int mnt_err)
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ocfs2_disable_quotas(osb);
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/* All dquots should be freed by now */
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WARN_ON(!llist_empty(&osb->dquot_drop_list));
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/* Wait for worker to be done with the work structure in osb */
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cancel_work_sync(&osb->dquot_drop_work);
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ocfs2_shutdown_local_alloc(osb);
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/* This will disable recovery and flush any recovery work. */
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@ -2276,6 +2281,9 @@ static int ocfs2_initialize_super(struct super_block *sb,
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INIT_WORK(&osb->dentry_lock_work, ocfs2_drop_dl_inodes);
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osb->dentry_lock_list = NULL;
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INIT_WORK(&osb->dquot_drop_work, ocfs2_drop_dquot_refs);
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init_llist_head(&osb->dquot_drop_list);
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/* get some pseudo constants for clustersize bits */
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osb->s_clustersize_bits =
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le32_to_cpu(di->id2.i_super.s_clustersize_bits);
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