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>

1 files changed, 17 insertions, 20 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index a313e9baeed0..41f1f713b7ba 100644
--- 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",