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- In a Giantless world, the vn_lock() in vcanrecycle() could legitimately

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fail.  Remove the panic from that case and document why it might fail.
 - Document the reason for calling cache_purge() on a newly created vnode.
 - In insmntque() order the operations so that we can call mtx_unlock()
   one fewer times.  This makes the code somewhat clearer as well.
 - Add XXX comments in sched_sync() and vflush().
 - In vget(), do not sleep while waiting for XLOCK to clear if LK_NOWAIT is
   set.
 - In vclean() we don't need to acquire a lock around a single TAILQ_FIRST
   call.  It's ok if we race here, the vinvalbuf will just do nothing.
 - Increase the scope of the lock in vgonel() to reduce the number of lock
   operations that are performed.
This commit is contained in:
jeff 2003-10-04 15:10:40 +00:00
parent 5adad3d54f
commit e30e11bb12
1 changed files with 22 additions and 21 deletions
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43
sys/kern/vfs_subr.c
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@ -818,15 +818,12 @@ vcanrecycle(struct vnode *vp, struct mount **vnmpp)
/* Don't recycle if we can't get the interlock */
if (!VI_TRYLOCK(vp))
return (EWOULDBLOCK);
/* We should be able to immediately acquire this */
/* XXX This looks like it should panic if it fails */
if (vn_lock(vp, LK_INTERLOCK | LK_EXCLUSIVE, td) != 0) {
if (VOP_ISLOCKED(vp, td))
panic("vcanrecycle: locked vnode");
/*
* This vnode may found and locked via some other list, if so we
* can't recycle it yet.
*/
if (vn_lock(vp, LK_INTERLOCK | LK_EXCLUSIVE | LK_NOWAIT, td) != 0)
return (EWOULDBLOCK);
}
/*
* Don't recycle if its filesystem is being suspended.
*/
@ -1008,7 +1005,7 @@ getnewvnode(tag, mp, vops, vpp)
vp->v_dd = vp;
vp->v_vnlock = &vp->v_lock;
lockinit(vp->v_vnlock, PVFS, tag, VLKTIMEOUT, LK_NOPAUSE);
cache_purge(vp);
cache_purge(vp); /* Sets up v_id. */
LIST_INIT(&vp->v_cache_src);
TAILQ_INIT(&vp->v_cache_dst);
}
@ -1059,12 +1056,10 @@ insmntque(vp, mp)
/*
* Insert into list of vnodes for the new mount point, if available.
*/
if ((vp->v_mount = mp) == NULL) {
mtx_unlock(&mntvnode_mtx);
return;
if ((vp->v_mount = mp) != NULL) {
TAILQ_INSERT_TAIL(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
mp->mnt_nvnodelistsize++;
}
TAILQ_INSERT_TAIL(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
mp->mnt_nvnodelistsize++;
mtx_unlock(&mntvnode_mtx);
}
@ -1713,6 +1708,10 @@ sched_sync(void)
syncer_delayno = 0;
while ((vp = LIST_FIRST(slp)) != NULL) {
/*
* XXX we have no guarantees about this vnodes
* identity due to a lack of interlock.
*/
mtx_unlock(&sync_mtx);
if (VOP_ISLOCKED(vp, NULL) == 0 &&
vn_start_write(vp, &mp, V_NOWAIT) == 0) {
@ -2084,8 +2083,10 @@ vget(vp, flags, td)
if ((flags & LK_INTERLOCK) == 0)
VI_LOCK(vp);
if (vp->v_iflag & VI_XLOCK && vp->v_vxproc != curthread) {
vp->v_iflag |= VI_XWANT;
msleep(vp, VI_MTX(vp), PINOD | PDROP, "vget", 0);
if ((flags & LK_NOWAIT) == 0) {
vp->v_iflag |= VI_XWANT;
msleep(vp, VI_MTX(vp), PINOD | PDROP, "vget", 0);
}
return (ENOENT);
}
@ -2368,6 +2369,10 @@ vflush(mp, rootrefs, flags)
VI_LOCK(vp);
mtx_unlock(&mntvnode_mtx);
/*
* XXX Does not check vn_lock error. Should restart loop if
* error == ENOENT.
*/
vn_lock(vp, LK_INTERLOCK | LK_EXCLUSIVE | LK_RETRY, td);
/*
* This vnode could have been reclaimed while we were
@ -2530,9 +2535,7 @@ vclean(vp, flags, td)
*/
if (flags & DOCLOSE) {
struct buf *bp;
VI_LOCK(vp);
bp = TAILQ_FIRST(&vp->v_dirtyblkhd);
VI_UNLOCK(vp);
if (bp != NULL)
(void) vn_write_suspend_wait(vp, NULL, V_WAIT);
if (vinvalbuf(vp, V_SAVE, NOCRED, td, 0, 0) != 0)
@ -2731,13 +2734,12 @@ vgonel(vp, td)
* If special device, remove it from special device alias list
* if it is on one.
*/
VI_LOCK(vp);
if (vp->v_type == VCHR && vp->v_rdev != NULL && vp->v_rdev != NODEV) {
VI_LOCK(vp);
mtx_lock(&spechash_mtx);
SLIST_REMOVE(&vp->v_rdev->si_hlist, vp, vnode, v_specnext);
vp->v_rdev->si_usecount -= vp->v_usecount;
mtx_unlock(&spechash_mtx);
VI_UNLOCK(vp);
vp->v_rdev = NULL;
}
@ -2751,7 +2753,6 @@ vgonel(vp, td)
* incremented first, vgone would (incorrectly) try to
* close the previous instance of the underlying object.
*/
VI_LOCK(vp);
if (vp->v_usecount == 0 && !(vp->v_iflag & VI_DOOMED)) {
mtx_lock(&vnode_free_list_mtx);
if (vp->v_iflag & VI_FREE) {