ceph: wake up writer if vmtruncate work get blocked

To write data, the writer first acquires the i_mutex, then try getting
caps. The writer may sleep while holding the i_mutex. If the MDS revokes
Fb cap in this case, vmtruncate work can't do its job because i_mutex
is locked. We should wake up the writer and let it truncate the pages.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 4906ada4a97c..55aaddb4047e 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1465,7 +1465,14 @@ static void ceph_vmtruncate_work(struct work_struct *work)
         struct inode *inode = &ci->vfs_inode;
 
         dout("vmtruncate_work %p\n", inode);
-        mutex_lock(&inode->i_mutex);
+        if (!mutex_trylock(&inode->i_mutex)) {
+                /*
+                 * the i_mutex can be hold by a writer who is waiting for
+                 * caps. wake up waiters, they will do pending vmtruncate.
+                 */
+                wake_up_all(&ci->i_cap_wq);
+                mutex_lock(&inode->i_mutex);
+        }
         __ceph_do_pending_vmtruncate(inode);
         mutex_unlock(&inode->i_mutex);
         iput(inode);