[PATCH] ceph: fix sync read eof check deadlock

[majianpeng <majianpeng@gmail.com>]

As Yan,Zheng said, commit 0913444208db intruoduce a bug:"getattr need to
"read lock" inode's filelock. But the lock can be in unstable state.
the getattr request waits for lock's state to become stable, the lock
waits for client to release Fr cap."

Commit 6a026589ba333185c466c90 resolved the same bug also.
Before doing getattr, it must put the caps which already hold avoid
deadlock.

Reported-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
---
 fs/ceph/file.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 7da35c7..bc00ace 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -839,7 +839,15 @@ again:
 		ret = ceph_sync_read(iocb, &i, &checkeof);
 
 		if (checkeof && ret >= 0) {
-			int statret = ceph_do_getattr(inode,
+			int statret;
+			/*
+			 *Before getattr,it should put caps avoid
+			 *deadlock.
+			 */
+			ceph_put_cap_refs(ci, got);
+			got = 0;
+
+			statret = ceph_do_getattr(inode,
 						      CEPH_STAT_CAP_SIZE);
 
 			/* hit EOF or hole? */
@@ -851,16 +859,23 @@ again:
 
 				read += ret;
 				checkeof = 0;
-				goto again;
+				ret = ceph_get_caps(ci, CEPH_CAP_FILE_RD,
+							want, &got, -1);
+				if (ret < 0)
+					ret = 0;
+				else
+					goto again;
 			}
 		}
 
 	} else
 		ret = generic_file_aio_read(iocb, iov, nr_segs, pos);
 
-	dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
-	     inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);
-	ceph_put_cap_refs(ci, got);
+	if (got) {
+		dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
+		     inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);
+		ceph_put_cap_refs(ci, got);
+	}
 
 	if (ret >= 0)
 		ret += read;
-- 
1.8.4-rc0