Commit 0f439c74 authored by Yan, Zheng's avatar Yan, Zheng Committed by Ilya Dryomov
Browse files

ceph: fix race of queuing delayed caps 



When called with CHECK_CAPS_AUTHONLY flag, ceph_check_caps() only
processes auth caps. In that case, it's unsafe to remove inode
from mdsc->cap_delay_list, because there can be delayed non-auth
caps.

Besides, ceph_check_caps() may lock/unlock i_ceph_lock several
times, when multiple threads call ceph_check_caps() at the same
time. It's possible that one thread calls __cap_delay_requeue(),
another thread calls __cap_delay_cancel(). __cap_delay_cancel()
should be called at very beginning of ceph_check_caps(), so that
it does not race with __cap_delay_requeue().

Signed-off-by: default avatar"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent ee612d95

fs/ceph/caps.c

+16 −17
Original line number Diff line number Diff line
@@ -902,6 +902,11 @@ int __ceph_caps_mds_wanted(struct ceph_inode_info *ci, bool check) 
/*

 * called under i_ceph_lock

 */

static int __ceph_is_single_caps(struct ceph_inode_info *ci)

{

	return rb_first(&ci->i_caps) == rb_last(&ci->i_caps);

}



static int __ceph_is_any_caps(struct ceph_inode_info *ci)

{

	return !RB_EMPTY_ROOT(&ci->i_caps);
@@ -1715,21 +1720,24 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags, 
	int mds = -1;   /* keep track of how far we've gone through i_caps list

			   to avoid an infinite loop on retry */

	struct rb_node *p;

	int delayed = 0, sent = 0, num;

	bool is_delayed = flags & CHECK_CAPS_NODELAY;

	int delayed = 0, sent = 0;

	bool no_delay = flags & CHECK_CAPS_NODELAY;

	bool queue_invalidate = false;

	bool force_requeue = false;

	bool tried_invalidate = false;



	/* if we are unmounting, flush any unused caps immediately. */

	if (mdsc->stopping)

		is_delayed = true;

		no_delay = true;



	spin_lock(&ci->i_ceph_lock);



	if (ci->i_ceph_flags & CEPH_I_FLUSH)

		flags |= CHECK_CAPS_FLUSH;



	if (!(flags & CHECK_CAPS_AUTHONLY) ||

	    (ci->i_auth_cap && __ceph_is_single_caps(ci)))

		__cap_delay_cancel(mdsc, ci);



	goto retry_locked;

retry:

	spin_lock(&ci->i_ceph_lock);
@@ -1784,7 +1792,7 @@ retry_locked: 
	 * have cached pages, but don't want them, then try to invalidate.

	 * If we fail, it's because pages are locked.... try again later.

	 */

	if ((!is_delayed || mdsc->stopping) &&

	if ((!no_delay || mdsc->stopping) &&

	    !S_ISDIR(inode->i_mode) &&		/* ignore readdir cache */

	    !(ci->i_wb_ref || ci->i_wrbuffer_ref) &&   /* no dirty pages... */

	    inode->i_data.nrpages &&		/* have cached pages */
@@ -1801,10 +1809,8 @@ retry_locked: 
		goto retry_locked;

	}



	num = 0;

	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {

		cap = rb_entry(p, struct ceph_cap, ci_node);

		num++;



		/* avoid looping forever */

		if (mds >= cap->mds ||
@@ -1867,7 +1873,7 @@ retry_locked: 
		    cap->mds_wanted == want)

			continue;     /* nope, all good */



		if (is_delayed)

		if (no_delay)

			goto ack;



		/* delay? */
@@ -1958,15 +1964,8 @@ ack: 
		goto retry; /* retake i_ceph_lock and restart our cap scan. */

	}



	/*

	 * Reschedule delayed caps release if we delayed anything,

	 * otherwise cancel.

	 */

	if (delayed && is_delayed)

		force_requeue = true;   /* __send_cap delayed release; requeue */

	if (!delayed && !is_delayed)

		__cap_delay_cancel(mdsc, ci);

	else if (!is_delayed || force_requeue)

	/* Reschedule delayed caps release if we delayed anything */

	if (delayed)

		__cap_delay_requeue(mdsc, ci);



	spin_unlock(&ci->i_ceph_lock);

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