Commit a7437954 authored by Xiubo Li's avatar Xiubo Li Committed by Ilya Dryomov
Browse files

ceph: try to queue a writeback if revoking fails 

If the pagecaches writeback just finished and the i_wrbuffer_ref
reaches zero it will try to trigger ceph_check_caps(). But if just
before ceph_check_caps() the i_wrbuffer_ref could be increased
again by mmap/cache write, then the Fwb revoke will fail.

We need to try to queue a writeback in this case instead of
triggering the writeback by BDI's delayed work per 5 seconds.

URL: https://tracker.ceph.com/issues/46904
URL: https://tracker.ceph.com/issues/55377


Signed-off-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 55ab5520

fs/ceph/caps.c

+24 −4
Original line number Diff line number Diff line
@@ -1911,6 +1911,7 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
	struct rb_node *p;

	bool queue_invalidate = false;

	bool tried_invalidate = false;

	bool queue_writeback = false;



	if (session)

		ceph_get_mds_session(session);
@@ -2063,12 +2064,29 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
		}



		/* completed revocation? going down and there are no caps? */

		if (revoking && (revoking & cap_used) == 0) {

		if (revoking) {

			if ((revoking & cap_used) == 0) {

				dout("completed revocation of %s\n",

				      ceph_cap_string(cap->implemented & ~cap->issued));

				goto ack;

			}



			/*

			 * If the "i_wrbuffer_ref" was increased by mmap or generic

			 * cache write just before the ceph_check_caps() is called,

			 * the Fb capability revoking will fail this time. Then we

			 * must wait for the BDI's delayed work to flush the dirty

			 * pages and to release the "i_wrbuffer_ref", which will cost

			 * at most 5 seconds. That means the MDS needs to wait at

			 * most 5 seconds to finished the Fb capability's revocation.

			 *

			 * Let's queue a writeback for it.

			 */

			if (S_ISREG(inode->i_mode) && ci->i_wrbuffer_ref &&

			    (revoking & CEPH_CAP_FILE_BUFFER))

				queue_writeback = true;

		}



		/* want more caps from mds? */

		if (want & ~cap->mds_wanted) {

			if (want & ~(cap->mds_wanted | cap->issued))
@@ -2136,6 +2154,8 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
	spin_unlock(&ci->i_ceph_lock);



	ceph_put_mds_session(session);

	if (queue_writeback)

		ceph_queue_writeback(inode);

	if (queue_invalidate)

		ceph_queue_invalidate(inode);

}