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Commit e3a767b6 authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
Browse files

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: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarMark Fasheh <mfasheh@suse.de>
Reviewed-by: default avatarSrinivas Eeda <srinivas.eeda@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9f985cb6

fs/ocfs2/ocfs2.h

+5 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ 
#include <linux/sched.h>

#include <linux/wait.h>

#include <linux/list.h>

#include <linux/llist.h>

#include <linux/rbtree.h>

#include <linux/workqueue.h>

#include <linux/kref.h>
@@ -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 */

fs/ocfs2/quota.h

+2 −0
Original line number Diff line number Diff line
@@ -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;

fs/ocfs2/quota_global.c

+35 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <linux/jiffies.h>

#include <linux/writeback.h>

#include <linux/workqueue.h>

#include <linux/llist.h>



#include <cluster/masklog.h>
@@ -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;

fs/ocfs2/super.c

+8 −0
Original line number Diff line number Diff line
@@ -1941,6 +1941,11 @@ 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. */
@@ -2276,6 +2281,9 @@ 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);