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>

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 4906ada4a97c6be9f00ce45245911dbb6efa98c2..55aaddb4047ea9ca01dc9d0ea203e562e58dccd8 100644 (file)
--- 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);