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Make vnd(4) work on sparse files:

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- Make the strategy decision a device flag and set VNF_USE_VN_RDWR for
  files known to be sparse.
- Change handle_with_rdwr() to use POSIX_FADV_NOREUSE advise to disable
  read ahead and keep the size of mapped pages below 1 MByte.

No objections on tech-kern@.
This commit is contained in:
hannken 2011-06-29 09:12:42 +00:00
parent 5c7719af90
commit 117bf62eb2
2 changed files with 23 additions and 12 deletions
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32
sys/dev/vnd.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: vnd.c,v 1.217 2011/06/12 03:35:51 rmind Exp $ */
/* $NetBSD: vnd.c,v 1.218 2011/06/29 09:12:42 hannken Exp $ */
/*-
* Copyright (c) 1996, 1997, 1998, 2008 The NetBSD Foundation, Inc.
@ -91,7 +91,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vnd.c,v 1.217 2011/06/12 03:35:51 rmind Exp $");
__KERNEL_RCSID(0, "$NetBSD: vnd.c,v 1.218 2011/06/29 09:12:42 hannken Exp $");
#if defined(_KERNEL_OPT)
#include "opt_vnd.h"
@ -549,7 +549,6 @@ static void
vndthread(void *arg)
{
struct vnd_softc *vnd = arg;
bool usestrategy;
int s;
/* Determine whether we can *use* VOP_BMAP and VOP_STRATEGY to
@ -557,12 +556,14 @@ vndthread(void *arg)
* operations to avoid messing with the local buffer cache.
* Otherwise fall back to regular VOP_READ/VOP_WRITE operations
* which are guaranteed to work with any file system. */
usestrategy = vnode_has_strategy(vnd);
if ((vnd->sc_flags & VNF_USE_VN_RDWR) == 0 &&
! vnode_has_strategy(vnd))
vnd->sc_flags |= VNF_USE_VN_RDWR;
#ifdef DEBUG
if (vnddebug & VDB_INIT)
printf("vndthread: vp %p, %s\n", vnd->sc_vp,
usestrategy ?
(vnd->sc_flags & VNF_USE_VN_RDWR) == 0 ?
"using bmap/strategy operations" :
"using read/write operations");
#endif
@ -644,7 +645,7 @@ vndthread(void *arg)
BIO_COPYPRIO(bp, obp);
/* Handle the request using the appropriate operations. */
if (usestrategy)
if ((vnd->sc_flags & VNF_USE_VN_RDWR) == 0)
handle_with_strategy(vnd, obp, bp);
else
handle_with_rdwr(vnd, obp, bp);
@ -696,11 +697,12 @@ handle_with_rdwr(struct vnd_softc *vnd, const struct buf *obp, struct buf *bp)
{
bool doread;
off_t offset;
size_t resid;
size_t len, resid;
struct vnode *vp;
doread = bp->b_flags & B_READ;
offset = obp->b_rawblkno * vnd->sc_dkdev.dk_label->d_secsize;
len = bp->b_bcount;
vp = vnd->sc_vp;
#if defined(DEBUG)
@ -716,10 +718,18 @@ handle_with_rdwr(struct vnd_softc *vnd, const struct buf *obp, struct buf *bp)
/* Issue the read or write operation. */
bp->b_error =
vn_rdwr(doread ? UIO_READ : UIO_WRITE,
vp, bp->b_data, bp->b_bcount, offset,
UIO_SYSSPACE, 0, vnd->sc_cred, &resid, NULL);
vp, bp->b_data, len, offset, UIO_SYSSPACE,
IO_ADV_ENCODE(POSIX_FADV_NOREUSE), vnd->sc_cred, &resid, NULL);
bp->b_resid = resid;
/* Keep mapped pages below threshold. */
mutex_enter(vp->v_interlock);
if (vp->v_uobj.uo_npages > 1024*1024 / PAGE_SIZE)
(void) VOP_PUTPAGES(vp, 0, 0,
PGO_ALLPAGES | PGO_CLEANIT | PGO_FREE | PGO_SYNCIO);
else
mutex_exit(vp->v_interlock);
/* We need to increase the number of outputs on the vnode if
* there was any write to it. */
if (!doread) {
@ -1076,8 +1086,8 @@ vndioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
if (!error && nd.ni_vp->v_type != VREG)
error = EOPNOTSUPP;
if (!error && vattr.va_bytes < vattr.va_size)
/* File is definitely sparse, reject here */
error = EINVAL;
/* File is definitely sparse, use vn_rdwr() */
vnd->sc_flags |= VNF_USE_VN_RDWR;
if (error) {
VOP_UNLOCK(nd.ni_vp);
goto close_and_exit;

3
sys/dev/vndvar.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: vndvar.h,v 1.30 2011/02/08 20:20:26 rmind Exp $ */
/* $NetBSD: vndvar.h,v 1.31 2011/06/29 09:12:42 hannken Exp $ */
/*-
* Copyright (c) 1996, 1997, 1998 The NetBSD Foundation, Inc.
@ -142,6 +142,7 @@ struct vnd_softc {
#define VNF_VUNCONF 0x200 /* device is unconfiguring */
#define VNF_COMP 0x400 /* file is compressed */
#define VNF_CLEARING 0x800 /* unit is being torn down */
#define VNF_USE_VN_RDWR 0x1000 /* have to use vn_rdwr() */
/* structure of header in a compressed file */
struct vnd_comp_header