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author | mdf <mdf@FreeBSD.org> | 2010-06-11 17:03:26 +0000 |
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committer | mdf <mdf@FreeBSD.org> | 2010-06-11 17:03:26 +0000 |
commit | 09830f0c6f6176f6e31316658158ef9f89afb842 (patch) | |
tree | f8d3891a1ce51c848f38a113365c3c5280b65285 /sys/kern | |
parent | 972d4b6a91487a21f17e0c177eb6e6d6c2f5ee48 (diff) | |
download | FreeBSD-src-09830f0c6f6176f6e31316658158ef9f89afb842.zip FreeBSD-src-09830f0c6f6176f6e31316658158ef9f89afb842.tar.gz |
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.
Reviewed by: jeff
Approved by: zml (mentor)
Diffstat (limited to 'sys/kern')
-rw-r--r-- | sys/kern/vfs_bio.c | 64 |
1 files changed, 54 insertions, 10 deletions
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c index 5429b14..df8bf66 100644 --- a/sys/kern/vfs_bio.c +++ b/sys/kern/vfs_bio.c @@ -393,10 +393,16 @@ runningbufwakeup(struct buf *bp) */ static __inline void -bufcountwakeup(void) +bufcountwakeup(struct buf *bp) { - - atomic_add_int(&numfreebuffers, 1); + int old; + + 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; @@ -592,7 +598,7 @@ 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); @@ -686,6 +692,7 @@ 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((bp->b_flags & B_REMFREE) == 0, @@ -696,8 +703,13 @@ 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)); + } } /* @@ -723,6 +735,8 @@ 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(bp->b_qindex != QUEUE_NONE, @@ -745,8 +759,13 @@ 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)); + } } @@ -1448,7 +1467,7 @@ brelse(struct buf *bp) */ if (!(bp->b_flags & B_DELWRI)) - bufcountwakeup(); + bufcountwakeup(bp); /* * Something we can maybe free or reuse @@ -1537,7 +1556,7 @@ 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. @@ -1916,6 +1935,8 @@ 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; @@ -4103,4 +4124,27 @@ DB_SHOW_COMMAND(vnodebufs, db_show_vnodebufs) 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 */ |