Commit 6a92b08f authored by Jeff Layton's avatar Jeff Layton Committed by Ilya Dryomov
Browse files

ceph: don't take s_mutex or snap_rwsem in ceph_check_caps 



These locks appear to be completely unnecessary. Almost all of this
function is done under the inode->i_ceph_lock, aside from the actual
sending of the message. Don't take either lock in this function.

Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarLuis Henriques <lhenriques@suse.de>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 52d60f8e

fs/ceph/caps.c

+11 −61
Original line number Diff line number Diff line
@@ -1912,7 +1912,6 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
	struct ceph_cap *cap;

	u64 flush_tid, oldest_flush_tid;

	int file_wanted, used, cap_used;

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

	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 */
@@ -1920,14 +1919,13 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
	bool queue_invalidate = false;

	bool tried_invalidate = false;



	if (session)

		ceph_get_mds_session(session);



	spin_lock(&ci->i_ceph_lock);

	if (ci->i_ceph_flags & CEPH_I_FLUSH)

		flags |= CHECK_CAPS_FLUSH;



	goto retry_locked;

retry:

	spin_lock(&ci->i_ceph_lock);

retry_locked:

	/* Caps wanted by virtue of active open files. */

	file_wanted = __ceph_caps_file_wanted(ci);
@@ -2007,7 +2005,7 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
			ci->i_rdcache_revoking = ci->i_rdcache_gen;

		}

		tried_invalidate = true;

		goto retry_locked;

		goto retry;

	}



	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
@@ -2021,8 +2019,6 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
		    ((flags & CHECK_CAPS_AUTHONLY) && cap != ci->i_auth_cap))

			continue;



		/* NOTE: no side-effects allowed, until we take s_mutex */



		/*

		 * If we have an auth cap, we don't need to consider any

		 * overlapping caps as used.
@@ -2085,37 +2081,8 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
			continue;     /* nope, all good */



ack:

		if (session && session != cap->session) {

			dout("oops, wrong session %p mutex\n", session);

			mutex_unlock(&session->s_mutex);

			session = NULL;

		}

		if (!session) {

			session = cap->session;

			if (mutex_trylock(&session->s_mutex) == 0) {

				dout("inverting session/ino locks on %p\n",

				     session);

				session = ceph_get_mds_session(session);

				spin_unlock(&ci->i_ceph_lock);

				if (took_snap_rwsem) {

					up_read(&mdsc->snap_rwsem);

					took_snap_rwsem = 0;

				}

				if (session) {

					mutex_lock(&session->s_mutex);

		ceph_put_mds_session(session);

				} else {

					/*

					 * Because we take the reference while

					 * holding the i_ceph_lock, it should

					 * never be NULL. Throw a warning if it

					 * ever is.

					 */

					WARN_ON_ONCE(true);

				}

				goto retry;

			}

		}

		session = ceph_get_mds_session(cap->session);



		/* kick flushing and flush snaps before sending normal

		 * cap message */
@@ -2127,21 +2094,8 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
			if (ci->i_ceph_flags & CEPH_I_FLUSH_SNAPS)

				__ceph_flush_snaps(ci, session);



			goto retry_locked;

		}



		/* take snap_rwsem after session mutex */

		if (!took_snap_rwsem) {

			if (down_read_trylock(&mdsc->snap_rwsem) == 0) {

				dout("inverting snap/in locks on %p\n",

				     inode);

				spin_unlock(&ci->i_ceph_lock);

				down_read(&mdsc->snap_rwsem);

				took_snap_rwsem = 1;

			goto retry;

		}

			took_snap_rwsem = 1;

		}



		if (cap == ci->i_auth_cap && ci->i_dirty_caps) {

			flushing = ci->i_dirty_caps;
@@ -2162,9 +2116,10 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 


		__prep_cap(&arg, cap, CEPH_CAP_OP_UPDATE, mflags, cap_used,

			   want, retain, flushing, flush_tid, oldest_flush_tid);

		spin_unlock(&ci->i_ceph_lock);



		spin_unlock(&ci->i_ceph_lock);

		__send_cap(&arg, ci);

		spin_lock(&ci->i_ceph_lock);



		goto retry; /* retake i_ceph_lock and restart our cap scan. */

	}
@@ -2179,13 +2134,9 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 


	spin_unlock(&ci->i_ceph_lock);



	ceph_put_mds_session(session);

	if (queue_invalidate)

		ceph_queue_invalidate(inode);



	if (session)

		mutex_unlock(&session->s_mutex);

	if (took_snap_rwsem)

		up_read(&mdsc->snap_rwsem);

}



/*
@@ -3550,13 +3501,12 @@ static void handle_cap_grant(struct inode *inode, 
	if (wake)

		wake_up_all(&ci->i_cap_wq);



	mutex_unlock(&session->s_mutex);

	if (check_caps == 1)

		ceph_check_caps(ci, CHECK_CAPS_AUTHONLY | CHECK_CAPS_NOINVAL,

				session);

	else if (check_caps == 2)

		ceph_check_caps(ci, CHECK_CAPS_NOINVAL, session);

	else

		mutex_unlock(&session->s_mutex);

}



/*