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Commit cdc2ce05 authored by Sage Weil's avatar Sage Weil
Browse files

ceph: fix session locking in handle_caps, ceph_check_caps 



Passing a session pointer to ceph_check_caps() used to mean it would leave
the session mutex locked.  That wasn't always possible if it wasn't passed
CHECK_CAPS_AUTHONLY.   If could unlock the passed session and lock a
differet session mutex, which was clearly wrong, and also emitted a
warning when it a racing CPU retook it and we did an unlock from the wrong
context.

This was only a problem when there was more than one MDS.

First, make ceph_check_caps unconditionally drop the session mutex, so that
it is free to lock other sessions as needed.  Then adjust the one caller
that passes in a session (handle_cap_grant) accordingly.

Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent 4ea0043a

fs/ceph/caps.c

+9 −5
Original line number Diff line number Diff line
@@ -1407,6 +1407,7 @@ static int try_nonblocking_invalidate(struct inode *inode) 
 */

void ceph_check_caps(struct ceph_inode_info *ci, int flags,

		     struct ceph_mds_session *session)

	__releases(session->s_mutex)

{

	struct ceph_client *client = ceph_inode_to_client(&ci->vfs_inode);

	struct ceph_mds_client *mdsc = &client->mdsc;
@@ -1414,7 +1415,6 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
	struct ceph_cap *cap;

	int file_wanted, used;

	int took_snap_rwsem = 0;             /* true if mdsc->snap_rwsem held */

	int drop_session_lock = session ? 0 : 1;

	int issued, implemented, want, retain, revoking, flushing = 0;

	int mds = -1;   /* keep track of how far we've gone through i_caps list

			   to avoid an infinite loop on retry */
@@ -1639,7 +1639,7 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
	if (queue_invalidate)

		ceph_queue_invalidate(inode);



	if (session && drop_session_lock)

	if (session)

		mutex_unlock(&session->s_mutex);

	if (took_snap_rwsem)

		up_read(&mdsc->snap_rwsem);
@@ -2688,14 +2688,17 @@ void ceph_handle_caps(struct ceph_mds_session *session, 
	case CEPH_CAP_OP_REVOKE:

	case CEPH_CAP_OP_GRANT:

		r = handle_cap_grant(inode, h, session, cap, msg->middle);

		if (r == 1)

		if (r == 1) {

			ceph_check_caps(ceph_inode(inode),

					CHECK_CAPS_NODELAY|CHECK_CAPS_AUTHONLY,

					session);

		else if (r == 2)

			session = NULL;

		} else if (r == 2) {

			ceph_check_caps(ceph_inode(inode),

					CHECK_CAPS_NODELAY,

					session);

			session = NULL;

		}

		break;



	case CEPH_CAP_OP_FLUSH_ACK:
@@ -2713,6 +2716,7 @@ void ceph_handle_caps(struct ceph_mds_session *session, 
	}



done:

	if (session)

		mutex_unlock(&session->s_mutex);



	if (check_caps)