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ocfs2: implement delayed dropping of last dquot reference

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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>
This commit is contained in:
Jan Kara
2014-04-03 14:46:56 -07:00
committed by Linus Torvalds
parent 9f985cb6c4
commit e3a767b60f
4 changed files with 50 additions and 0 deletions
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2
fs/ocfs2/quota.h
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@@ -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;