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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: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Yan, Zheng 2018-01-08 14:44:10 +08:00 committed by Ilya Dryomov
parent ee612d954f
commit 0f439c746c
1 changed files with 16 additions and 17 deletions
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33
fs/ceph/caps.c
View File

@ -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);