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- for pagecache dependency, track which page in the block 

has been written or not individually by (ab)using b_resid
  in pcbp as a bitmap.
- add a comment to explain why it's needed.

PR/15364.  reviewed by Chuck Silvers.
This commit is contained in:
yamt 2005-09-09 15:04:07 +00:00
parent 5b4c989faf
commit d8798fec66
1 changed files with 27 additions and 13 deletions
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40
sys/ufs/ffs/ffs_softdep.c
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@ -1,4 +1,4 @@
/* $NetBSD: ffs_softdep.c,v 1.69 2005/08/30 22:01:12 xtraeme Exp $ */
/* $NetBSD: ffs_softdep.c,v 1.70 2005/09/09 15:04:07 yamt Exp $ */
/*
* Copyright 1998 Marshall Kirk McKusick. All Rights Reserved.
@ -33,7 +33,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ffs_softdep.c,v 1.69 2005/08/30 22:01:12 xtraeme Exp $");
__KERNEL_RCSID(0, "$NetBSD: ffs_softdep.c,v 1.70 2005/09/09 15:04:07 yamt Exp $");
#include <sys/param.h>
#include <sys/buf.h>
@ -197,6 +197,9 @@ void softdep_pageiodone(struct buf *);
void softdep_flush_vnode(struct vnode *, daddr_t);
static void softdep_trackbufs(struct inode *, int, boolean_t);
#define PCBP_BITMAP(off, size) \
(((1 << howmany((size), PAGE_SIZE)) - 1) << ((off) >> PAGE_SHIFT))
/*
* Exported softdep operations.
*/
@ -5793,6 +5796,11 @@ softdep_setup_pagecache(ip, lbn, size)
* Enter pagecache dependency buf in hash.
* Always reset b_resid to be the full amount of data in the block
* since the caller has the corresponding pages locked and dirty.
*
* Note that we are using b_resid as a bitmap, so that
* we can track which pages are written. As pages can be re-dirtied
* and re-written in the mean time, byte-count is not suffice for
* our purpose.
*/
bp = softdep_lookup_pcbp(vp, lbn);
@ -5804,9 +5812,13 @@ softdep_setup_pagecache(ip, lbn, size)
LIST_INSERT_HEAD(&pcbphashhead[PCBPHASH(vp, lbn)], bp, b_hash);
LIST_INSERT_HEAD(&ip->i_pcbufhd, bp, b_vnbufs);
}
bp->b_bcount = bp->b_resid = size;
bp->b_bcount = size;
KASSERT(size <= PAGE_SIZE * sizeof(bp->b_resid) * CHAR_BIT);
bp->b_resid = PCBP_BITMAP(0, size);
UVMHIST_LOG(ubchist, "vp = %p, lbn = %ld, "
"bp = %p, bcount = resid = %ld", vp, lbn, bp, size);
"bp = %p, bcount = %ld", vp, lbn, bp, size);
UVMHIST_LOG(ubchist, "b_resid = %ld",
bp->b_resid, 0, 0, 0);
return bp;
}
@ -5933,7 +5945,7 @@ softdep_pageiodone1(bp)
struct worklist *wk;
daddr_t lbn;
voff_t off;
long iosize = bp->b_bcount;
int iosize = bp->b_bcount;
int size, asize, bshift, bsize;
int i;
UVMHIST_FUNC("softdep_pageiodone"); UVMHIST_CALLED(ubchist);
@ -5946,12 +5958,14 @@ softdep_pageiodone1(bp)
for (i = 0; i < npages; i++) {
pg = uvm_pageratop((vaddr_t)bp->b_data + (i << PAGE_SHIFT));
if (pg == NULL) {
continue;
panic("%s: no page", __func__);
}
for (off = pg->offset;
off < pg->offset + PAGE_SIZE;
off += bsize) {
int pgmask;
size = MIN(asize, iosize);
iosize -= size;
lbn = off >> bshift;
@ -5968,14 +5982,14 @@ softdep_pageiodone1(bp)
UVMHIST_LOG(ubchist,
"pcbp %p iosize %ld, size %d, asize %d",
pcbp, iosize, size, asize);
pcbp->b_resid -= size;
if (pcbp->b_resid < 0) {
panic("softdep_pageiodone: "
"resid < 0, vp %p lbn 0x%" PRIx64 " pcbp %p"
" iosize %ld, size %d, asize %d, bsize %d",
vp, lbn, pcbp, iosize, size, asize, bsize);
pgmask = PCBP_BITMAP(off & (bsize - 1), size);
if ((~pcbp->b_resid & pgmask) != 0) {
UVMHIST_LOG(ubchist,
"multiple write resid %lx, pgmask %lx",
pcbp->b_resid, pgmask, 0, 0);
}
if (pcbp->b_resid > 0) {
pcbp->b_resid &= ~pgmask;
if (pcbp->b_resid != 0) {
continue;
}