Author: mdf
Date: Mon Sep 13 17:23:18 2010
New Revision: 212563
URL: http://svn.freebsd.org/changeset/base/212563
Log:
MFC r209053:
Add INVARIANTS checking that numfreebufs values are sane. Also add a
per-buf flag to catch if a buf is double-counted in the free count.
This code was useful to debug an instance where a local patch at Isilon
was incorrectly managing numfreebufs for a new buf state.
Modified:
stable/7/sys/kern/vfs_bio.c
stable/7/sys/sys/buf.h
Directory Properties:
stable/7/sys/ (props changed)
stable/7/sys/cddl/contrib/opensolaris/ (props changed)
stable/7/sys/contrib/dev/acpica/ (props changed)
stable/7/sys/contrib/pf/ (props changed)
Modified: stable/7/sys/kern/vfs_bio.c
==============================================================================
--- stable/7/sys/kern/vfs_bio.c Mon Sep 13 17:18:49 2010 (r212562)
+++ stable/7/sys/kern/vfs_bio.c Mon Sep 13 17:23:18 2010 (r212563)
@@ -381,10 +381,16 @@ runningbufwakeup(struct buf *bp)
*/
static __inline void
-bufcountwakeup(void)
+bufcountwakeup(struct buf *bp)
{
+ int old;
- atomic_add_int(&numfreebuffers, 1);
+ KASSERT((bp->b_vflags & BV_INFREECNT) == 0,
+ ("buf %p already counted as free", bp));
+ bp->b_vflags |= BV_INFREECNT;
+ old = atomic_fetchadd_int(&numfreebuffers, 1);
+ KASSERT(old >= 0 && old < nbuf,
+ ("numfreebuffers climbed to %d", old + 1));
mtx_lock(&nblock);
if (needsbuffer) {
needsbuffer &= ~VFS_BIO_NEED_ANY;
@@ -587,7 +593,7 @@ bufinit(void)
bp->b_rcred = NOCRED;
bp->b_wcred = NOCRED;
bp->b_qindex = QUEUE_EMPTY;
- bp->b_vflags = 0;
+ bp->b_vflags = BV_INFREECNT; /* buf is counted as free */
bp->b_xflags = 0;
LIST_INIT(&bp->b_dep);
BUF_LOCKINIT(bp);
@@ -688,6 +694,7 @@ bfreekva(struct buf *bp)
void
bremfree(struct buf *bp)
{
+ int old;
CTR3(KTR_BUF, "bremfree(%p) vp %p flags %X", bp, bp->b_vp, bp->b_flags);
KASSERT(BUF_REFCNT(bp), ("bremfree: buf must be locked."));
@@ -698,8 +705,13 @@ bremfree(struct buf *bp)
bp->b_flags |= B_REMFREE;
/* Fixup numfreebuffers count. */
- if ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0)
- atomic_subtract_int(&numfreebuffers, 1);
+ if ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0) {
+ KASSERT((bp->b_vflags & BV_INFREECNT) != 0,
+ ("buf %p not counted in numfreebuffers", bp));
+ bp->b_vflags &= ~BV_INFREECNT;
+ old = atomic_fetchadd_int(&numfreebuffers, -1);
+ KASSERT(old > 0, ("numfreebuffers dropped to %d", old - 1));
+ }
}
/*
@@ -725,6 +737,8 @@ bremfreef(struct buf *bp)
static void
bremfreel(struct buf *bp)
{
+ int old;
+
CTR3(KTR_BUF, "bremfreel(%p) vp %p flags %X",
bp, bp->b_vp, bp->b_flags);
KASSERT(BUF_REFCNT(bp), ("bremfreel: buffer %p not locked.", bp));
@@ -747,8 +761,13 @@ bremfreel(struct buf *bp)
* delayed-write, the buffer was free and we must decrement
* numfreebuffers.
*/
- if ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0)
- atomic_subtract_int(&numfreebuffers, 1);
+ if ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0) {
+ KASSERT((bp->b_vflags & BV_INFREECNT) != 0,
+ ("buf %p not counted in numfreebuffers", bp));
+ bp->b_vflags &= ~BV_INFREECNT;
+ old = atomic_fetchadd_int(&numfreebuffers, -1);
+ KASSERT(old > 0, ("numfreebuffers dropped to %d", old - 1));
+ }
}
@@ -1452,7 +1471,7 @@ brelse(struct buf *bp)
*/
if (!(bp->b_flags & B_DELWRI))
- bufcountwakeup();
+ bufcountwakeup(bp);
/*
* Something we can maybe free or reuse
@@ -1542,7 +1561,7 @@ bqrelse(struct buf *bp)
mtx_unlock(&bqlock);
if ((bp->b_flags & B_INVAL) || !(bp->b_flags & B_DELWRI))
- bufcountwakeup();
+ bufcountwakeup(bp);
/*
* Something we can maybe free or reuse.
@@ -1922,6 +1941,8 @@ restart:
bp->b_flags = 0;
bp->b_ioflags = 0;
bp->b_xflags = 0;
+ KASSERT((bp->b_vflags & BV_INFREECNT) == 0,
+ ("buf %p still counted as free?", bp));
bp->b_vflags = 0;
bp->b_vp = NULL;
bp->b_blkno = bp->b_lblkno = 0;
@@ -4083,4 +4104,27 @@ DB_SHOW_COMMAND(vnodebufs, db_show_vnode
db_printf("\n");
}
}
+
+DB_COMMAND(countfreebufs, db_coundfreebufs)
+{
+ struct buf *bp;
+ int i, used = 0, nfree = 0;
+
+ if (have_addr) {
+ db_printf("usage: countfreebufs\n");
+ return;
+ }
+
+ for (i = 0; i < nbuf; i++) {
+ bp = &buf[i];
+ if ((bp->b_vflags & BV_INFREECNT) != 0)
+ nfree++;
+ else
+ used++;
+ }
+
+ db_printf("Counted %d free, %d used (%d tot)\n", nfree, used,
+ nfree + used);
+ db_printf("numfreebuffers is %d\n", numfreebuffers);
+}
#endif /* DDB */
Modified: stable/7/sys/sys/buf.h
==============================================================================
--- stable/7/sys/sys/buf.h Mon Sep 13 17:18:49 2010 (r212562)
+++ stable/7/sys/sys/buf.h Mon Sep 13 17:23:18 2010 (r212563)
@@ -247,6 +247,7 @@ struct buf {
#define BV_SCANNED 0x00000001 /* VOP_FSYNC funcs mark written
bufs */
#define BV_BKGRDINPROG 0x00000002 /* Background write in progress
*/
#define BV_BKGRDWAIT 0x00000004 /* Background write waiting */
+#define BV_INFREECNT 0x80000000 /* buf is counted in
numfreebufs */
#ifdef _KERNEL
/*
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