Author: kib
Date: Sun Oct 6 06:09:43 2013
New Revision: 256077
URL: http://svnweb.freebsd.org/changeset/base/256077
Log:
MFC r255941:
Increase the chance of the buffer write from the bufdaemon helper
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.
Modified:
stable/9/sys/kern/vfs_bio.c
Directory Properties:
stable/9/sys/ (props changed)
Modified: stable/9/sys/kern/vfs_bio.c
==============================================================================
--- stable/9/sys/kern/vfs_bio.c Sun Oct 6 06:05:11 2013 (r256076)
+++ stable/9/sys/kern/vfs_bio.c Sun Oct 6 06:09:43 2013 (r256077)
@@ -2671,6 +2671,8 @@ flushbufqueues(struct vnode *lvp, int qu
int hasdeps;
int flushed;
int target;
+ int error;
+ bool unlock;
if (lvp == NULL) {
target = numdirtybuffers - lodirtybuffers;
@@ -2751,7 +2753,16 @@ flushbufqueues(struct vnode *lvp, int qu
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_TRYUPGRADE);
+ }
+ if (error == 0) {
mtx_unlock(&bqlock);
CTR3(KTR_BUF, "flushbufqueue(%p) vp %p flags %X",
bp, bp->b_vp, bp->b_flags);
@@ -2763,7 +2774,8 @@ flushbufqueues(struct vnode *lvp, int qu
notbufdflashes++;
}
vn_finished_write(mp);
- VOP_UNLOCK(vp, 0);
+ if (unlock)
+ VOP_UNLOCK(vp, 0);
flushwithdeps += hasdeps;
flushed++;
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