svn commit: r223988 - head/sys/fs/devfs
Konstantin Belousov
kib at FreeBSD.org
Wed Jul 13 21:07:41 UTC 2011
Author: kib
Date: Wed Jul 13 21:07:41 2011
New Revision: 223988
URL: http://svn.freebsd.org/changeset/base/223988
Log:
While fixing the looping of a thread while devfs vnode is reclaimed,
r179247 introduced a possibility of devfs_allocv() returning spurious
ENOENT. If the vnode is selected by vnlru daemon for reclamation, then
devfs_allocv() can get ENOENT from vget() due to devfs_close() dropping
vnode lock around the call to cdevsw d_close method.
Use LK_RETRY in the vget() call, and do some part of the devfs_reclaim()
work in devfs_allocv(), clearing vp->v_data and de->de_vnode. Retry the
allocation of the vnode, now with de->de_vnode == NULL.
The check vp->v_data == NULL at the start of devfs_close() cannot be
affected by the change, since vnode lock must be held while VI_DOOMED
is set, and only dropped after the check.
Reported and tested by: Kohji Okuno <okuno.kohji jp panasonic com>
Reviewed by: attilio
MFC after: 3 weeks
Modified:
head/sys/fs/devfs/devfs_vnops.c
Modified: head/sys/fs/devfs/devfs_vnops.c
==============================================================================
--- head/sys/fs/devfs/devfs_vnops.c Wed Jul 13 21:06:46 2011 (r223987)
+++ head/sys/fs/devfs/devfs_vnops.c Wed Jul 13 21:07:41 2011 (r223988)
@@ -397,6 +397,7 @@ devfs_allocv(struct devfs_dirent *de, st
sx_xunlock(&dmp->dm_lock);
return (ENOENT);
}
+loop:
DEVFS_DE_HOLD(de);
DEVFS_DMP_HOLD(dmp);
mtx_lock(&devfs_de_interlock);
@@ -405,16 +406,21 @@ devfs_allocv(struct devfs_dirent *de, st
VI_LOCK(vp);
mtx_unlock(&devfs_de_interlock);
sx_xunlock(&dmp->dm_lock);
- error = vget(vp, lockmode | LK_INTERLOCK, curthread);
+ vget(vp, lockmode | LK_INTERLOCK | LK_RETRY, curthread);
sx_xlock(&dmp->dm_lock);
if (devfs_allocv_drop_refs(0, dmp, de)) {
- if (error == 0)
- vput(vp);
+ vput(vp);
return (ENOENT);
}
- else if (error) {
- sx_xunlock(&dmp->dm_lock);
- return (error);
+ else if ((vp->v_iflag & VI_DOOMED) != 0) {
+ mtx_lock(&devfs_de_interlock);
+ if (de->de_vnode == vp) {
+ de->de_vnode = NULL;
+ vp->v_data = NULL;
+ }
+ mtx_unlock(&devfs_de_interlock);
+ vput(vp);
+ goto loop;
}
sx_xunlock(&dmp->dm_lock);
*vpp = vp;
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