ceph: fix snap context reference leaks

The get_oldest_context() helper takes a reference to the returned snap
context, but most callers weren't dropping that reference.  Fix them.

Also drop the unused locked __get_oldest_context() variant.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index a313e9b..41f1f71 100644 (file)
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -336,16 +336,15 @@ out:
 /*
  * Get ref for the oldest snapc for an inode with dirty data... that is, the
  * only snap context we are allowed to write back.
- *
- * Caller holds i_lock.
  */
-static struct ceph_snap_context *__get_oldest_context(struct inode *inode,
-                                                     u64 *snap_size)
+static struct ceph_snap_context *get_oldest_context(struct inode *inode,
+                                                   u64 *snap_size)
 {
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_snap_context *snapc = NULL;
        struct ceph_cap_snap *capsnap = NULL;
 
+       spin_lock(&inode->i_lock);
        list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
                dout(" cap_snap %p snapc %p has %d dirty pages\n", capsnap,
                     capsnap->context, capsnap->dirty_pages);
@@ -361,16 +360,6 @@ static struct ceph_snap_context *__get_oldest_context(struct inode *inode,
                dout(" head snapc %p has %d dirty pages\n",
                     snapc, ci->i_wrbuffer_ref_head);
        }
-       return snapc;
-}
-
-static struct ceph_snap_context *get_oldest_context(struct inode *inode,
-                                                   u64 *snap_size)
-{
-       struct ceph_snap_context *snapc = NULL;
-
-       spin_lock(&inode->i_lock);
-       snapc = __get_oldest_context(inode, snap_size);
        spin_unlock(&inode->i_lock);
        return snapc;
 }
@@ -391,7 +380,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
        int len = PAGE_CACHE_SIZE;
        loff_t i_size;
        int err = 0;
-       struct ceph_snap_context *snapc;
+       struct ceph_snap_context *snapc, *oldest;
        u64 snap_size = 0;
        long writeback_stat;
 
@@ -412,13 +401,16 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
                dout("writepage %p page %p not dirty?\n", inode, page);
                goto out;
        }
-       if (snapc->seq > get_oldest_context(inode, &snap_size)->seq) {
+       oldest = get_oldest_context(inode, &snap_size);
+       if (snapc->seq > oldest->seq) {
                dout("writepage %p page %p snapc %p not writeable - noop\n",
                     inode, page, (void *)page->private);
                /* we should only noop if called by kswapd */
                WARN_ON((current->flags & PF_MEMALLOC) == 0);
+               ceph_put_snap_context(oldest);
                goto out;
        }
+       ceph_put_snap_context(oldest);
 
        /* is this a partial page at end of file? */
        if (snap_size)
@@ -457,7 +449,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
        ClearPagePrivate(page);
        end_page_writeback(page);
        ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
-       ceph_put_snap_context(snapc);
+       ceph_put_snap_context(snapc);  /* page's reference */
 out:
        return err;
 }
@@ -914,7 +906,10 @@ static int context_is_writeable_or_written(struct inode *inode,
                                           struct ceph_snap_context *snapc)
 {
        struct ceph_snap_context *oldest = get_oldest_context(inode, NULL);
-       return !oldest || snapc->seq <= oldest->seq;
+       int ret = !oldest || snapc->seq <= oldest->seq;
+
+       ceph_put_snap_context(oldest);
+       return ret;
 }
 
 /*
@@ -957,13 +952,14 @@ retry_locked:
                up_read(&mdsc->snap_rwsem);
 
                if (snapc->seq > oldest->seq) {
+                       ceph_put_snap_context(oldest);
                        dout(" page %p snapc %p not current or oldest\n",
-                            page, (void *)page->private);
+                            page, snapc);
                        /*
                         * queue for writeback, and wait for snapc to
                         * be writeable or written
                         */
-                       snapc = ceph_get_snap_context((void *)page->private);
+                       snapc = ceph_get_snap_context(snapc);
                        unlock_page(page);
                        ceph_queue_writeback(inode);
                        r = wait_event_interruptible(ci->i_cap_wq,
@@ -973,6 +969,7 @@ retry_locked:
                                return r;
                        return -EAGAIN;
                }
+               ceph_put_snap_context(oldest);
 
                /* yay, writeable, do it now (without dropping page lock) */
                dout(" page %p snapc %p not current, but oldest\n",