[PATCH 2/2] ceph: wake up writer if vmtruncate work get blocked

["Yan, Zheng" <zheng.z.yan@intel.com>]

From: "Yan, Zheng" <zheng.z.yan@intel.com>

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>
---
 fs/ceph/inode.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 4906ada..55aaddb 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);
-- 
1.8.1.4