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Avoid several race conditions, especially when a transaction ends in error. 

Guard sw_reg_start() against synchronous completions of the device
strategy routines, avoiding possibly boundless recursion.
This commit is contained in:
pk 1997-11-29 00:35:43 +00:00
parent 9f8ad690b4
commit 46f604677d
1 changed files with 72 additions and 37 deletions
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109
sys/vm/vm_swap.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: vm_swap.c,v 1.48 1997/11/04 21:24:22 thorpej Exp $ */
/* $NetBSD: vm_swap.c,v 1.49 1997/11/29 00:35:43 pk Exp $ */
/*
* Copyright (c) 1995, 1996, 1997 Matthew R. Green
@ -261,6 +261,9 @@ struct vndxfer {
struct swapdev *vx_sdp;
int vx_error;
int vx_pending; /* # of pending aux buffers */
int vx_flags;
#define VX_BUSY 1
#define VX_DEAD 2
};
@ -1037,7 +1040,6 @@ sw_reg_strategy(sdp, bp, bn)
int bn;
{
struct vnode *vp;
struct vndbuf *nbp;
struct vndxfer *vnx;
daddr_t nbn;
caddr_t addr;
@ -1053,12 +1055,16 @@ sw_reg_strategy(sdp, bp, bn)
/* Allocate a header for this transfer and link it to the buffer */
getvndxfer(vnx);
vnx->vx_flags = VX_BUSY;
vnx->vx_error = 0;
vnx->vx_pending = 0;
vnx->vx_bp = bp;
vnx->vx_sdp = sdp;
error = 0;
for (resid = bp->b_resid; resid; resid -= sz) {
struct vndbuf *nbp;
nra = 0;
error = VOP_BMAP(sdp->swd_vp, bn / sdp->swd_bsize,
&vp, &nbn, &nra);
@ -1076,16 +1082,9 @@ sw_reg_strategy(sdp, bp, bn)
* a hassle (in the write case).
*/
if (error) {
vnx->vx_error = error;
s = splbio();
if (vnx->vx_pending == 0) {
bp->b_error = error;
bp->b_flags |= B_ERROR;
putvndxfer(vnx);
biodone(bp);
}
splx(s);
return;
vnx->vx_error = error;
goto out;
}
if ((off = bn % sdp->swd_bsize) != 0)
@ -1144,18 +1143,33 @@ sw_reg_strategy(sdp, bp, bn)
*/
nbp->vb_buf.b_cylinder = nbp->vb_buf.b_blkno;
s = splbio();
if (vnx->vx_error != 0) {
putvndbuf(nbp);
goto out;
}
vnx->vx_pending++;
bgetvp(vp, &nbp->vb_buf);
disksort(&sdp->swd_tab, &nbp->vb_buf);
if (sdp->swd_tab.b_active < sdp->swd_maxactive) {
sdp->swd_tab.b_active++;
sw_reg_start(sdp);
}
sw_reg_start(sdp);
splx(s);
bn += sz;
addr += sz;
}
s = splbio();
out: /* Arrive here at splbio */
vnx->vx_flags &= ~VX_BUSY;
if (vnx->vx_pending == 0) {
if (vnx->vx_error != 0) {
bp->b_error = vnx->vx_error;
bp->b_flags |= B_ERROR;
}
putvndxfer(vnx);
biodone(bp);
}
splx(s);
}
/*
@ -1169,18 +1183,31 @@ sw_reg_start(sdp)
struct swapdev *sdp;
{
struct buf *bp;
static int busy; /* Recursion control */
bp = sdp->swd_tab.b_actf;
sdp->swd_tab.b_actf = bp->b_actf;
if (busy != 0)
return;
busy = 1;
while (sdp->swd_tab.b_active < sdp->swd_maxactive) {
bp = sdp->swd_tab.b_actf;
if (bp == NULL)
break;
sdp->swd_tab.b_actf = bp->b_actf;
sdp->swd_tab.b_active++;
#ifdef SWAPDEBUG
if (vmswapdebug & VMSDB_SWFLOW)
printf("sw_reg_start: bp %p vp %p blkno %x addr %p cnt %lx\n",
if (vmswapdebug & VMSDB_SWFLOW)
printf(
"sw_reg_start: bp %p vp %p blkno %x addr %p cnt %lx\n",
bp, bp->b_vp, bp->b_blkno,bp->b_data, bp->b_bcount);
#endif
if ((bp->b_flags & B_READ) == 0)
bp->b_vp->v_numoutput++;
VOP_STRATEGY(bp);
if ((bp->b_flags & B_READ) == 0)
bp->b_vp->v_numoutput++;
VOP_STRATEGY(bp);
}
busy = 0;
}
static void
@ -1226,24 +1253,32 @@ sw_reg_iodone(bp)
* Wrap up this transaction if it has run to completion or, in
* case of an error, when all auxiliary buffers have returned.
*/
if (pbp->b_resid == 0 || (vnx->vx_error && vnx->vx_pending == 0)) {
if (vnx->vx_error != 0) {
pbp->b_flags |= B_ERROR;
pbp->b_error = vnx->vx_error;
if (vnx->vx_error != 0) {
pbp->b_flags |= B_ERROR;
pbp->b_error = vnx->vx_error;
if ((vnx->vx_flags & VX_BUSY) == 0 && vnx->vx_pending == 0) {
putvndxfer(vnx);
biodone(pbp);
}
putvndxfer(vnx);
#ifdef SWAPDEBUG
if (vmswapdebug & VMSDB_SWFLOW)
printf("swiodone: pbp %p iodone\n", pbp);
#endif
biodone(pbp);
}
if (sdp->swd_tab.b_actf)
sw_reg_start(sdp);
else
sdp->swd_tab.b_active--;
if (pbp->b_resid == 0) {
if (vnx->vx_pending != 0)
panic("swiodone: vnx pending: %d", vnx->vx_pending);
if ((vnx->vx_flags & VX_BUSY) == 0) {
putvndxfer(vnx);
#ifdef SWAPDEBUG
if (vmswapdebug & VMSDB_SWFLOW)
printf("swiodone: pbp %p iodone\n", pbp);
#endif
biodone(pbp);
}
}
sdp->swd_tab.b_active--;
sw_reg_start(sdp);
splx(s);
}