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Increase the chance of the buffer write from the bufdaemon helper

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context to succeed.  If the locked vnode which owns the buffer to be
written is shared locked, try the non-blocking upgrade of the lock to
exclusive.

PR:	kern/178997
Reported and tested by:	Klaus Weber <fbsd-bugs-2013-1@unix-admin.de>
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Approved by:	re (marius)
This commit is contained in:
kib 2013-09-22 19:23:48 +00:00
parent c4b7751552
commit 46dd93739b
1 changed files with 14 additions and 2 deletions
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16
sys/kern/vfs_bio.c
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@ -2624,6 +2624,8 @@ flushbufqueues(struct vnode *lvp, int target, int flushdeps)
int hasdeps;
int flushed;
int queue;
int error;
bool unlock;
flushed = 0;
queue = QUEUE_DIRTY;
@ -2699,7 +2701,16 @@ flushbufqueues(struct vnode *lvp, int target, int flushdeps)
BUF_UNLOCK(bp);
continue;
}
if (vn_lock(vp, LK_EXCLUSIVE | LK_NOWAIT | LK_CANRECURSE) == 0) {
if (lvp == NULL) {
unlock = true;
error = vn_lock(vp, LK_EXCLUSIVE | LK_NOWAIT);
} else {
ASSERT_VOP_LOCKED(vp, "getbuf");
unlock = false;
error = VOP_ISLOCKED(vp) == LK_EXCLUSIVE ? 0 :
vn_lock(vp, LK_UPGRADE | LK_NOWAIT);
}
if (error == 0) {
mtx_unlock(&bqdirty);
CTR3(KTR_BUF, "flushbufqueue(%p) vp %p flags %X",
bp, bp->b_vp, bp->b_flags);
@ -2711,7 +2722,8 @@ flushbufqueues(struct vnode *lvp, int target, int flushdeps)
notbufdflushes++;
}
vn_finished_write(mp);
VOP_UNLOCK(vp, 0);
if (unlock)
VOP_UNLOCK(vp, 0);
flushwithdeps += hasdeps;
flushed++;