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authorhannken <hannken@NetBSD.org>2003-12-10 11:40:11 +0000
committerhannken <hannken@NetBSD.org>2003-12-10 11:40:11 +0000
commitfbae381aaa42360e3c45875f461e67347695bf0c (patch)
tree439c3e235211813e723a33d5ce4c2bb334d19aa5 /sys/dev
parent4949a9ae53dc245b0d8240bd4851bbd22d085019 (diff)
The file system snapshot pseudo driver.
Uses a hook in spec_strategy() to save data written from a mounted file system to its block device and a hook in dounmount(). Not enabled by default in any kernel config. Approved by: Frank van der Linden <fvdl@netbsd.org>
Diffstat (limited to 'sys/dev')
-rw-r--r--sys/dev/Makefile4
-rw-r--r--sys/dev/fss.c1215
-rw-r--r--sys/dev/fssvar.h163
3 files changed, 1380 insertions, 2 deletions
diff --git a/sys/dev/Makefile b/sys/dev/Makefile
index f3f5b0541e3..592a2a9d26e 100644
--- a/sys/dev/Makefile
+++ b/sys/dev/Makefile
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.17 2003/10/10 06:14:02 grog Exp $
+# $NetBSD: Makefile,v 1.18 2003/12/10 11:40:11 hannken Exp $
SUBDIR= apm ata dec dmover hpc i2o ic ieee1394 ir isa ofw \
pci pckbc pcmcia raidframe sbus scsipi sun tc usb vme wscons vinum
@@ -6,6 +6,6 @@ SUBDIR= apm ata dec dmover hpc i2o ic ieee1394 ir isa ofw \
INCSDIR= /usr/include/dev
# Only install includes which are used by userland
-INCS= ccdvar.h cgdvar.h kttcpio.h md.h vndvar.h
+INCS= ccdvar.h cgdvar.h fssvar.h kttcpio.h md.h vndvar.h
.include <bsd.kinc.mk>
diff --git a/sys/dev/fss.c b/sys/dev/fss.c
new file mode 100644
index 00000000000..29974d3739a
--- /dev/null
+++ b/sys/dev/fss.c
@@ -0,0 +1,1215 @@
+/* $NetBSD: fss.c,v 1.1 2003/12/10 11:40:11 hannken Exp $ */
+
+/*-
+ * Copyright (c) 2003 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Juergen Hannken-Illjes.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the NetBSD
+ * Foundation, Inc. and its contributors.
+ * 4. Neither the name of The NetBSD Foundation nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * File system snapshot disk driver.
+ *
+ * Block/character interface to the snapshot of a mounted file system.
+ */
+
+#include <sys/cdefs.h>
+__KERNEL_RCSID(0, "$NetBSD: fss.c,v 1.1 2003/12/10 11:40:11 hannken Exp $");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/namei.h>
+#include <sys/proc.h>
+#include <sys/errno.h>
+#include <sys/buf.h>
+#include <sys/malloc.h>
+#include <sys/ioctl.h>
+#include <sys/disklabel.h>
+#include <sys/device.h>
+#include <sys/disk.h>
+#include <sys/stat.h>
+#include <sys/mount.h>
+#include <sys/vnode.h>
+#include <sys/file.h>
+#include <sys/uio.h>
+#include <sys/conf.h>
+#include <sys/kthread.h>
+
+#include <miscfs/specfs/specdev.h>
+
+#include <machine/stdarg.h>
+
+#include "fss.h"
+#include <dev/fssvar.h>
+
+#ifdef DEBUG
+#include "opt_ddb.h"
+#include <ddb/ddbvar.h>
+#include <machine/db_machdep.h>
+#include <ddb/db_command.h>
+#include <ddb/db_interface.h>
+#endif
+
+#ifdef DEBUG
+#define FSS_STATISTICS
+#endif
+
+#ifdef FSS_STATISTICS
+struct fss_stat {
+ u_int64_t cow_calls;
+ u_int64_t cow_copied;
+ u_int64_t cow_cache_full;
+ u_int64_t indir_read;
+ u_int64_t indir_write;
+};
+
+static struct fss_stat fss_stat[NFSS];
+
+#define FSS_STAT_INC(sc, field) \
+ do { \
+ fss_stat[sc->sc_unit].field++; \
+ } while (0)
+#define FSS_STAT_SET(sc, field, value) \
+ do { \
+ fss_stat[sc->sc_unit].field = value; \
+ } while (0)
+#define FSS_STAT_ADD(sc, field, value) \
+ do { \
+ fss_stat[sc->sc_unit].field += value; \
+ } while (0)
+#define FSS_STAT_VAL(sc, field) fss_stat[sc->sc_unit].field
+#define FSS_STAT_CLEAR(sc) \
+ do { \
+ memset(&fss_stat[sc->sc_unit], 0, \
+ sizeof(struct fss_stat)); \
+ } while (0)
+#else /* FSS_STATISTICS */
+#define FSS_STAT_INC(sc, field)
+#define FSS_STAT_SET(sc, field, value)
+#define FSS_STAT_ADD(sc, field, value)
+#define FSS_STAT_CLEAR(sc)
+#endif /* FSS_STATISTICS */
+
+typedef enum {
+ FSS_READ,
+ FSS_WRITE
+} fss_io_type;
+
+static int fss_attached;
+
+void fssattach(int);
+int fssdetach(void);
+
+dev_type_open(fss_open);
+dev_type_close(fss_close);
+dev_type_read(fss_read);
+dev_type_write(fss_write);
+dev_type_ioctl(fss_ioctl);
+dev_type_strategy(fss_strategy);
+dev_type_dump(fss_dump);
+dev_type_size(fss_size);
+
+static inline void fss_error(struct fss_softc *, const char *, ...);
+static inline int fss_valid(struct fss_softc *);
+static int fss_create_snapshot(struct fss_softc *, struct fss_set *,
+ struct proc *);
+static int fss_delete_snapshot(struct fss_softc *, struct proc *);
+static int fss_softc_alloc(struct fss_softc *);
+static void fss_softc_free(struct fss_softc *);
+static void fss_cluster_iodone(struct buf *);
+static void fss_read_cluster(struct fss_softc *, u_int32_t);
+static int fss_write_cluster(struct fss_cache *, u_int32_t);
+static void fss_bs_thread(void *);
+static inline void block_to_cluster(struct fss_softc *, daddr_t, long,
+ u_int32_t *, long *);
+static int fss_bs_io(struct fss_softc *, fss_io_type,
+ u_int32_t, long, int, caddr_t);
+static u_int32_t *fss_bs_indir(struct fss_softc *, u_int32_t);
+
+const struct bdevsw fss_bdevsw = {
+ fss_open, fss_close, fss_strategy, fss_ioctl,
+ fss_dump, fss_size, D_DISK
+};
+
+const struct cdevsw fss_cdevsw = {
+ fss_open, fss_close, fss_read, fss_write, fss_ioctl,
+ nostop, notty, nopoll, nommap, nokqfilter, D_DISK
+};
+
+void
+fssattach(int num)
+{
+ int i;
+ struct fss_softc *sc;
+
+ if (fss_attached != 0)
+ return;
+
+ for (i = 0; i < NFSS; i++) {
+ sc = &fss_softc[i];
+ sc->sc_unit = i;
+ sc->sc_bdev = NODEV;
+ lockinit(&sc->sc_lock, PRIBIO, "fsslock", 0, 0);
+ bufq_alloc(&sc->sc_bufq, BUFQ_FCFS|BUFQ_SORT_RAWBLOCK);
+ }
+
+ fss_attached = 1;
+}
+
+int
+fssdetach(void)
+{
+ int i;
+
+ if (fss_attached == 0)
+ return 0;
+
+ for (i = 0; i < NFSS; i++)
+ if (fss_softc[i].sc_flags != 0)
+ return EBUSY;
+
+ for (i = 0; i < NFSS; i++)
+ bufq_free(&fss_softc[i].sc_bufq);
+
+ fss_attached = 0;
+
+ return 0;
+}
+
+int
+fss_open(dev_t dev, int flags, int mode, struct proc *p)
+{
+ struct fss_softc *sc;
+
+ if (fss_dev_to_softc(dev, &sc) != 0)
+ return ENXIO;
+
+ return 0;
+}
+
+int
+fss_close(dev_t dev, int flags, int mode, struct proc *p)
+{
+ struct fss_softc *sc;
+
+ if (fss_dev_to_softc(dev, &sc) != 0)
+ return ENXIO;
+
+ return 0;
+}
+
+void
+fss_strategy(struct buf *bp)
+{
+ struct fss_softc *sc;
+
+ if ((bp->b_flags & B_READ) != B_READ ||
+ fss_dev_to_softc(bp->b_dev, &sc) != 0 ||
+ !fss_valid(sc)) {
+ bp->b_error = ENXIO;
+ bp->b_flags |= B_ERROR;
+ bp->b_resid = bp->b_bcount;
+ biodone(bp);
+ return;
+ }
+
+ bp->b_rawblkno = bp->b_blkno;
+ BUFQ_PUT(&sc->sc_bufq, bp);
+ wakeup(&sc->sc_bs_proc);
+}
+
+int
+fss_read(dev_t dev, struct uio *uio, int flags)
+{
+ return physio(fss_strategy, NULL, dev, B_READ, minphys, uio);
+}
+
+int
+fss_write(dev_t dev, struct uio *uio, int flags)
+{
+ return physio(fss_strategy, NULL, dev, B_WRITE, minphys, uio);
+}
+
+int
+fss_ioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p)
+{
+ int error;
+ struct fss_softc *sc;
+ struct fss_set *fss = (struct fss_set *)data;
+ struct fss_get *fsg = (struct fss_get *)data;
+
+ if ((error = fss_dev_to_softc(dev, &sc)) != 0)
+ return error;
+
+ lockmgr(&sc->sc_lock, LK_EXCLUSIVE, NULL);
+
+ error = EINVAL;
+
+ switch (cmd) {
+ case FSSIOCSET:
+ if ((flag & FWRITE) == 0)
+ error = EPERM;
+ else if ((sc->sc_flags & FSS_ACTIVE) != 0)
+ error = EBUSY;
+ else
+ error = fss_create_snapshot(sc, fss, p);
+ break;
+
+ case FSSIOCCLR:
+ if ((flag & FWRITE) == 0)
+ error = EPERM;
+ else if ((sc->sc_flags & FSS_ACTIVE) == 0)
+ error = ENXIO;
+ else
+ error = fss_delete_snapshot(sc, p);
+ break;
+
+ case FSSIOCGET:
+ if ((sc->sc_flags & FSS_ACTIVE) == FSS_ACTIVE) {
+ memcpy(fsg->fsg_mount, sc->sc_mntname, MNAMELEN);
+ fsg->fsg_csize = sc->sc_clsize;
+ fsg->fsg_time = sc->sc_time;
+ fsg->fsg_mount_size = sc->sc_clcount;
+ fsg->fsg_bs_size = sc->sc_clnext;
+ error = 0;
+ } else
+ error = ENXIO;
+ break;
+ }
+
+ lockmgr(&sc->sc_lock, LK_RELEASE, NULL);
+
+ return error;
+}
+
+int
+fss_size(dev_t dev)
+{
+ return -1;
+}
+
+int
+fss_dump(dev_t dev, daddr_t blkno, caddr_t va, size_t size)
+{
+ return ENXIO;
+}
+
+/*
+ * An error occured reading or writing the snapshot or backing store.
+ * If it is the first error log to console.
+ */
+static inline void
+fss_error(struct fss_softc *sc, const char *fmt, ...)
+{
+ int s;
+ va_list ap;
+
+ s = splbio();
+ if ((sc->sc_flags & (FSS_ACTIVE|FSS_ERROR)) == FSS_ACTIVE) {
+ va_start(ap, fmt);
+ printf("fss%d: snapshot invalid: ", sc->sc_unit);
+ vprintf(fmt, ap);
+ printf("\n");
+ va_end(ap);
+ }
+ if ((sc->sc_flags & FSS_ACTIVE) == FSS_ACTIVE)
+ sc->sc_flags |= FSS_ERROR;
+ splx(s);
+}
+
+/*
+ * Check if this snapshot is still valid.
+ */
+static inline int
+fss_valid(struct fss_softc *sc)
+{
+ int s, valid;
+
+ s = splbio();
+ valid = ((sc->sc_flags & (FSS_ACTIVE|FSS_ERROR)) == FSS_ACTIVE);
+ splx(s);
+
+ return valid;
+}
+
+/*
+ * Allocate the variable sized parts of the softc and
+ * fork the kernel thread.
+ *
+ * The fields sc_clcount, sc_clsize, sc_cache_size and sc_indir_size
+ * must be initialized.
+ */
+static int
+fss_softc_alloc(struct fss_softc *sc)
+{
+ int i, len, error;
+
+ len = (sc->sc_clcount+NBBY-1)/NBBY;
+ sc->sc_copied = malloc(len, M_TEMP, M_ZERO|M_WAITOK);
+
+ len = sc->sc_cache_size*sizeof(struct fss_cache);
+ sc->sc_cache = malloc(len, M_TEMP, M_WAITOK);
+
+ len = sc->sc_clsize;
+ for (i = 0; i < sc->sc_cache_size; i++) {
+ sc->sc_cache[i].fc_type = FSS_CACHE_FREE;
+ sc->sc_cache[i].fc_softc = sc;
+ sc->sc_cache[i].fc_xfercount = 0;
+ sc->sc_cache[i].fc_data = malloc(len, M_TEMP, M_WAITOK);
+ }
+
+ len = (sc->sc_indir_size+NBBY-1)/NBBY;
+ sc->sc_indir_valid = malloc(len, M_TEMP, M_ZERO|M_WAITOK);
+
+ len = sc->sc_clsize;
+ sc->sc_indir_data = malloc(len, M_TEMP, M_ZERO|M_WAITOK);
+
+ if ((error = kthread_create1(fss_bs_thread, sc, &sc->sc_bs_proc,
+ "fssbs%d", sc->sc_unit)) != 0)
+ return error;
+
+ sc->sc_flags |= FSS_BS_THREAD;
+ return 0;
+}
+
+/*
+ * Free the variable sized parts of the softc.
+ */
+static void
+fss_softc_free(struct fss_softc *sc)
+{
+ int i;
+
+ if ((sc->sc_flags & FSS_BS_THREAD) != 0) {
+ sc->sc_flags &= ~FSS_BS_THREAD;
+ wakeup(&sc->sc_bs_proc);
+ while (sc->sc_bs_proc != NULL)
+ tsleep(sc, PRIBIO, "fssthread", 1);
+ }
+
+ if (sc->sc_copied != NULL)
+ free(sc->sc_copied, M_TEMP);
+ sc->sc_copied = NULL;
+
+ if (sc->sc_cache != NULL) {
+ for (i = 0; i < sc->sc_cache_size; i++)
+ free(sc->sc_cache[i].fc_data, M_TEMP);
+ free(sc->sc_cache, M_TEMP);
+ }
+ sc->sc_cache = NULL;
+
+ if (sc->sc_indir_valid != NULL)
+ free(sc->sc_indir_valid, M_TEMP);
+ sc->sc_indir_valid = NULL;
+
+ if (sc->sc_indir_data != NULL)
+ free(sc->sc_indir_data, M_TEMP);
+ sc->sc_indir_data = NULL;
+}
+
+/*
+ * Check if an unmount is ok. If forced, set this snapshot into ERROR state.
+ */
+int
+fss_umount_hook(struct mount *mp, int forced)
+{
+ int i, s;
+
+ s = splbio();
+ for (i = 0; i < NFSS; i++)
+ if ((fss_softc[i].sc_flags & FSS_ACTIVE) != 0 &&
+ fss_softc[i].sc_mount == mp) {
+ if (forced)
+ fss_error(&fss_softc[i], "forced unmount");
+ else {
+ splx(s);
+ return EBUSY;
+ }
+ }
+ splx(s);
+ return 0;
+}
+
+/*
+ * A buffer is written to the snapshotted block device. Copy to
+ * backing store if needed.
+ */
+void
+fss_copy_on_write(struct fss_softc *sc, struct buf *bp)
+{
+ u_int32_t cl, ch, c;
+
+#ifdef DIAGNOSTIC
+ /*
+ * Buffer written on a suspended file system. This is always an error.
+ */
+ if (sc->sc_mount &&
+ (sc->sc_mount->mnt_iflag & IMNT_SUSPENDED) == IMNT_SUSPENDED) {
+ printf_nolog("fss%d: write while suspended, %lu@%" PRId64 "\n",
+ sc->sc_unit, bp->b_bcount, bp->b_blkno);
+#ifdef DEBUG
+ db_stack_trace_print((db_expr_t)__builtin_frame_address(0),
+ TRUE, 65535, "", printf_nolog);
+#endif /* DEBUG */
+ }
+#endif /* DIAGNOSTIC */
+
+ if (!fss_valid(sc))
+ return;
+
+ sc->sc_cowcount++;
+
+ FSS_STAT_INC(sc, cow_calls);
+
+ block_to_cluster(sc, bp->b_blkno, 0, &cl, NULL);
+ block_to_cluster(sc, bp->b_blkno, bp->b_bcount-1, &ch, NULL);
+ for (c = cl; c <= ch; c++) {
+ if (!fss_valid(sc))
+ break;
+
+ fss_read_cluster(sc, c);
+ }
+
+ if (--sc->sc_cowcount == 0)
+ wakeup(&sc->sc_cowcount);
+}
+
+/*
+ * Lookup and open needed files.
+ *
+ * Returns dev and size of the underlying block device.
+ * Initialzes the fields sc_mntname, sc_bs_vp, sc_mount and sc_strategy
+ */
+static int
+fss_create_files(struct fss_softc *sc, struct fss_set *fss,
+ dev_t *bdev, off_t *bsize, struct proc *p)
+{
+ int error;
+ struct stat stat;
+ struct statfs statfs;
+ struct nameidata nd;
+ const struct bdevsw *bdevsw;
+
+ /*
+ * Get the mounted file system.
+ */
+
+ NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, fss->fss_mount, p);
+ if ((error = namei(&nd)) != 0)
+ return error;
+
+ if ((nd.ni_vp->v_flag & VROOT) != VROOT) {
+ vrele(nd.ni_vp);
+ return EINVAL;
+ }
+
+ sc->sc_mount = nd.ni_vp->v_mount;
+
+ /*
+ * Get the block device it is mounted on.
+ */
+
+ error = VFS_STATFS(sc->sc_mount, &statfs, p);
+ vrele(nd.ni_vp);
+ if (error != 0)
+ return error;
+
+ memcpy(sc->sc_mntname, statfs.f_mntonname, MNAMELEN);
+
+ NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, statfs.f_mntfromname, p);
+ if ((error = namei(&nd)) != 0)
+ return error;
+
+ if (nd.ni_vp->v_type != VBLK) {
+ vrele(nd.ni_vp);
+ return EINVAL;
+ }
+
+ if ((error = vn_stat(nd.ni_vp, &stat, p)) != 0) {
+ vrele(nd.ni_vp);
+ return error;
+ }
+
+ *bdev = nd.ni_vp->v_rdev;
+ *bsize = stat.st_size;
+ vrele(nd.ni_vp);
+
+ if ((bdevsw = bdevsw_lookup(*bdev)) == NULL)
+ return EINVAL;
+ sc->sc_strategy = bdevsw->d_strategy;
+
+ /*
+ * Get the backing store
+ */
+
+ NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, fss->fss_bstore, p);
+ if ((error = vn_open(&nd, FREAD|FWRITE, 0)) != 0)
+ return error;
+ VOP_UNLOCK(nd.ni_vp, 0);
+
+ sc->sc_bs_vp = nd.ni_vp;
+
+ if (nd.ni_vp->v_type != VREG && nd.ni_vp->v_type != VCHR)
+ return EINVAL;
+
+ if (nd.ni_vp->v_mount == sc->sc_mount)
+ return EDEADLK;
+
+ if (sc->sc_bs_vp->v_type == VREG) {
+ error = VFS_STATFS(sc->sc_bs_vp->v_mount, &statfs, p);
+ if (error != 0)
+ return error;
+ sc->sc_bs_bsize = statfs.f_iosize;
+ } else
+ sc->sc_bs_bsize = DEV_BSIZE;
+
+ /*
+ * As all IO to from/to the backing store goes through
+ * VOP_STRATEGY() clean the buffer cache to prevent
+ * cache incoherencies.
+ */
+ if ((error = vinvalbuf(sc->sc_bs_vp, V_SAVE, p->p_ucred, p, 0, 0)) != 0)
+ return error;
+
+ return 0;
+}
+
+/*
+ * Create a snapshot.
+ */
+static int
+fss_create_snapshot(struct fss_softc *sc, struct fss_set *fss, struct proc *p)
+{
+ int len, error;
+ dev_t bdev;
+ off_t bsize;
+
+ /*
+ * Open needed files.
+ */
+ if ((error = fss_create_files(sc, fss, &bdev, &bsize, p)) != 0)
+ goto bad;
+
+ /*
+ * Set parameters.
+ */
+ if (fss->fss_csize == 0)
+ sc->sc_clsize = MAXPHYS;
+ else if (fss->fss_csize < 0 || (fss->fss_csize & (DEV_BSIZE-1)) != 0) {
+ error = EINVAL;
+ goto bad;
+ } else if (bsize/fss->fss_csize > FSS_CLUSTER_MAX)
+ sc->sc_clsize = (bsize/FSS_CLUSTER_MAX+DEV_BSIZE-1) &
+ ~(DEV_BSIZE-1);
+ else
+ sc->sc_clsize = fss->fss_csize;
+
+ if (sc->sc_clsize <= 8192)
+ sc->sc_cache_size = 32;
+ else if (sc->sc_clsize <= 65536)
+ sc->sc_cache_size = 8;
+ else
+ sc->sc_cache_size = 4;
+
+ block_to_cluster(sc, btodb(bsize)-1, DEV_BSIZE-1,
+ &sc->sc_clcount, &sc->sc_cllast);
+ sc->sc_clcount += 1;
+ sc->sc_cllast += 1;
+
+ len = sc->sc_clcount*sizeof(u_int32_t);
+ sc->sc_indir_size = (len+sc->sc_clsize-1)/sc->sc_clsize;
+ sc->sc_clnext = sc->sc_indir_size;
+ sc->sc_indir_cur = 0;
+
+ if ((error = fss_softc_alloc(sc)) != 0)
+ goto bad;
+
+ /* XXX FSSNAP_PREPARE */
+
+ /*
+ * Activate the snapshot.
+ */
+
+ if ((error = vfs_write_suspend(sc->sc_mount)) != 0)
+ goto bad;
+
+ microtime(&sc->sc_time);
+
+ /* XXX FSSNAP_CREATE */
+
+ if (error == 0) {
+ sc->sc_flags |= FSS_ACTIVE;
+ sc->sc_bdev = bdev;
+ }
+
+ vfs_write_resume(sc->sc_mount);
+
+ if (error != 0)
+ goto bad;
+
+#ifdef DEBUG
+ printf("fss%d: %s snapshot active\n", sc->sc_unit, sc->sc_mntname);
+ printf("fss%d: %u clusters of %u, %u cache slots, %u indir clusters\n",
+ sc->sc_unit, sc->sc_clcount, sc->sc_clsize,
+ sc->sc_cache_size, sc->sc_indir_size);
+#endif
+
+ return 0;
+
+bad:
+ fss_softc_free(sc);
+ if (sc->sc_bs_vp != NULL)
+ vn_close(sc->sc_bs_vp, FREAD|FWRITE, p->p_ucred, p);
+ sc->sc_bs_vp = NULL;
+
+ return error;
+}
+
+/*
+ * Delete a snapshot.
+ */
+static int
+fss_delete_snapshot(struct fss_softc *sc, struct proc *p)
+{
+ int s;
+
+ s = splbio();
+ sc->sc_flags &= ~(FSS_ACTIVE|FSS_ERROR);
+ splx(s);
+
+ while (sc->sc_cowcount > 0) {
+ tsleep(&sc->sc_cowcount, PRIBIO, "cowwait1", 0);
+ }
+
+ sc->sc_mount = NULL;
+ sc->sc_bdev = NODEV;
+ fss_softc_free(sc);
+ vn_close(sc->sc_bs_vp, FREAD|FWRITE, p->p_ucred, p);
+ sc->sc_bs_vp = NULL;
+
+ /* XXX FSSNAP_DESTROY */
+
+ FSS_STAT_CLEAR(sc);
+
+ return 0;
+}
+
+/*
+ * Convert disk block with offset to backing store cluster with offset.
+ */
+static inline void
+block_to_cluster(struct fss_softc *sc, daddr_t blkno, long off,
+ u_int32_t *cblk, long *coff)
+{
+ blkno = dbtob(blkno)+off;
+ if (cblk != NULL)
+ *cblk = blkno/sc->sc_clsize;
+ if (coff != NULL)
+ *coff = blkno%sc->sc_clsize;
+}
+
+/*
+ * A read from the snapshotted block device has completed.
+ */
+static void
+fss_cluster_iodone(struct buf *bp)
+{
+ int s;
+ struct fss_cache *scp = bp->b_private;
+
+ s = splbio();
+
+ if (bp->b_flags & B_EINTR)
+ fss_error(scp->fc_softc, "fs read interrupted");
+ if (bp->b_flags & B_ERROR)
+ fss_error(scp->fc_softc, "fs read error %d", bp->b_error);
+
+ if (bp->b_vp != NULL)
+ brelvp(bp);
+
+ if (--scp->fc_xfercount == 0)
+ wakeup(&scp->fc_data);
+
+ pool_put(&bufpool, bp);
+
+ splx(s);
+}
+
+/*
+ * Read a cluster from the snapshotted block device to the cache.
+ */
+static void
+fss_read_cluster(struct fss_softc *sc, u_int32_t cl)
+{
+ int s, todo, len;
+ caddr_t addr;
+ daddr_t dblk;
+ struct buf *bp;
+ struct fss_cache *scp, *scl;
+
+ /*
+ * Get a free cache slot.
+ */
+ scl = sc->sc_cache+sc->sc_cache_size;
+
+restart:
+ if (isset(sc->sc_copied, cl)) {
+ return;
+ }
+
+ for (scp = sc->sc_cache; scp < scl; scp++)
+ if (scp->fc_type != FSS_CACHE_FREE &&
+ scp->fc_cluster == cl) {
+ tsleep(&scp->fc_type, PRIBIO, "cowwait2", 0);
+ goto restart;
+ }
+
+ for (scp = sc->sc_cache; scp < scl; scp++)
+ if (scp->fc_type == FSS_CACHE_FREE) {
+ scp->fc_type = FSS_CACHE_BUSY;
+ scp->fc_cluster = cl;
+ break;
+ }
+ if (scp >= scl) {
+ FSS_STAT_INC(sc, cow_cache_full);
+ tsleep(&sc->sc_cache, PRIBIO, "cowwait3", 0);
+ goto restart;
+ }
+
+ /*
+ * Start the read.
+ */
+ FSS_STAT_INC(sc, cow_copied);
+
+ dblk = cl*btodb(sc->sc_clsize);
+ addr = scp->fc_data;
+ if (cl == sc->sc_clcount-1) {
+ todo = sc->sc_cllast;
+ memset(addr+todo, 0, sc->sc_clsize-todo);
+ } else
+ todo = sc->sc_clsize;
+ while (todo > 0) {
+ len = todo;
+ if (len > MAXPHYS)
+ len = MAXPHYS;
+
+ s = splbio();
+ bp = pool_get(&bufpool, PR_WAITOK);
+ splx(s);
+
+ BUF_INIT(bp);
+ bp->b_flags = B_READ|B_CALL;
+ bp->b_bcount = len;
+ bp->b_bufsize = bp->b_bcount;
+ bp->b_error = 0;
+ bp->b_data = addr;
+ bp->b_blkno = bp->b_rawblkno = dblk;
+ bp->b_proc = NULL;
+ bp->b_dev = sc->sc_bdev;
+ bp->b_vp = NULLVP;
+ bp->b_private = scp;
+ bp->b_iodone = fss_cluster_iodone;
+
+ (*sc->sc_strategy)(bp);
+
+ s = splbio();
+ scp->fc_xfercount++;
+ splx(s);
+
+ dblk += btodb(len);
+ addr += len;
+ todo -= len;
+ }
+
+ /*
+ * Wait for all read requests to complete.
+ */
+ s = splbio();
+ while (scp->fc_xfercount > 0)
+ tsleep(&scp->fc_data, PRIBIO, "cowwait", 0);
+ splx(s);
+
+ scp->fc_type = FSS_CACHE_VALID;
+ setbit(sc->sc_copied, scp->fc_cluster);
+ wakeup(&sc->sc_bs_proc);
+}
+
+/*
+ * Write a cluster from the cache to the backing store.
+ */
+static int
+fss_write_cluster(struct fss_cache *scp, u_int32_t cl)
+{
+ int s, error, todo, len, nra;
+ daddr_t nbn;
+ caddr_t addr;
+ off_t pos;
+ struct buf *bp;
+ struct vnode *vp;
+ struct fss_softc *sc;
+
+ error = 0;
+ sc = scp->fc_softc;
+
+ pos = (off_t)cl*sc->sc_clsize;
+ addr = scp->fc_data;
+ todo = sc->sc_clsize;
+
+ while (todo > 0) {
+ vn_lock(sc->sc_bs_vp, LK_EXCLUSIVE|LK_RETRY);
+ error = VOP_BMAP(sc->sc_bs_vp, pos/sc->sc_bs_bsize,
+ &vp, &nbn, &nra);
+ VOP_UNLOCK(sc->sc_bs_vp, 0);
+ if (error == 0 && nbn == (daddr_t)-1)
+ error = EIO;
+ if (error)
+ break;
+
+ len = (nra+1)*sc->sc_bs_bsize-pos%sc->sc_bs_bsize;
+ if (len > todo)
+ len = todo;
+
+ s = splbio();
+ bp = pool_get(&bufpool, PR_WAITOK);
+ splx(s);
+
+ BUF_INIT(bp);
+ bp->b_flags = B_CALL;
+ bp->b_bcount = len;
+ bp->b_bufsize = bp->b_bcount;
+ bp->b_error = 0;
+ bp->b_data = addr;
+ bp->b_blkno = bp->b_rawblkno = nbn+btodb(pos%sc->sc_bs_bsize);
+ bp->b_proc = NULL;
+ bp->b_vp = NULLVP;
+ bp->b_private = scp;
+ bp->b_iodone = fss_cluster_iodone;
+ bgetvp(vp, bp);
+ bp->b_vp->v_numoutput++;
+
+ VOP_STRATEGY(bp);
+
+ s = splbio();
+ scp->fc_xfercount++;
+ splx(s);
+
+ pos += len;
+ addr += len;
+ todo -= len;
+ }
+
+ /*
+ * Wait for all write requests to complete.
+ */
+ s = splbio();
+ while (scp->fc_xfercount > 0)
+ tsleep(&scp->fc_data, PRIBIO, "bswwait", 0);
+ splx(s);
+
+ return error;
+}
+
+/*
+ * Read/write clusters from/to backing store.
+ */
+static int
+fss_bs_io(struct fss_softc *sc, fss_io_type rw,
+ u_int32_t cl, long off, int len, caddr_t data)
+{
+ int s, error, todo, count, nra;
+ off_t pos;
+ daddr_t nbn;
+ struct buf *bp;
+ struct vnode *vp;
+
+ todo = len;
+ pos = (off_t)cl*sc->sc_clsize+off;
+ error = 0;
+
+ while (todo > 0) {
+ vn_lock(sc->sc_bs_vp, LK_EXCLUSIVE|LK_RETRY);
+ error = VOP_BMAP(sc->sc_bs_vp, pos/sc->sc_bs_bsize,
+ &vp, &nbn, &nra);
+ VOP_UNLOCK(sc->sc_bs_vp, 0);
+ if (error == 0 && nbn == (daddr_t)-1)
+ error = EIO;
+ if (error)
+ break;
+
+ count = (nra+1)*sc->sc_bs_bsize-pos%sc->sc_bs_bsize;
+ if (count > todo)
+ count = todo;
+
+ s = splbio();
+ bp = pool_get(&bufpool, PR_WAITOK);
+ splx(s);
+
+ BUF_INIT(bp);
+ bp->b_flags = (rw == FSS_READ ? B_READ : 0);
+ bp->b_bcount = count;
+ bp->b_bufsize = bp->b_bcount;
+ bp->b_error = 0;
+ bp->b_data = data;
+ bp->b_blkno = bp->b_rawblkno = nbn+btodb(pos%sc->sc_bs_bsize);
+ bp->b_proc = NULL;
+ bp->b_vp = NULLVP;
+ bgetvp(vp, bp);
+ if ((bp->b_flags & B_READ) == 0)
+ bp->b_vp->v_numoutput++;
+ VOP_STRATEGY(bp);
+
+ error = biowait(bp);
+
+ if (bp->b_vp != NULL)
+ brelvp(bp);
+
+ s = splbio();
+ pool_put(&bufpool, bp);
+ splx(s);
+
+ if (error)
+ break;
+
+ todo -= count;
+ data += count;
+ pos += count;
+ }
+
+ return error;
+}
+
+/*
+ * Get a pointer to the indirect slot for this cluster.
+ */
+static u_int32_t *
+fss_bs_indir(struct fss_softc *sc, u_int32_t cl)
+{
+ u_int32_t icl;
+ int ioff;
+
+ icl = cl/(sc->sc_clsize/sizeof(u_int32_t));
+ ioff = cl%(sc->sc_clsize/sizeof(u_int32_t));
+
+ if (sc->sc_indir_cur == icl)
+ return &sc->sc_indir_data[ioff];
+
+ if (sc->sc_indir_dirty) {
+ FSS_STAT_INC(sc, indir_write);
+ if (fss_bs_io(sc, FSS_WRITE, sc->sc_indir_cur, 0,
+ sc->sc_clsize, (caddr_t)sc->sc_indir_data) != 0)
+ return NULL;
+ setbit(sc->sc_indir_valid, sc->sc_indir_cur);
+ }
+
+ sc->sc_indir_dirty = 0;
+ sc->sc_indir_cur = icl;
+
+ if (isset(sc->sc_indir_valid, sc->sc_indir_cur)) {
+ FSS_STAT_INC(sc, indir_read);
+ if (fss_bs_io(sc, FSS_READ, sc->sc_indir_cur, 0,
+ sc->sc_clsize, (caddr_t)sc->sc_indir_data) != 0)
+ return NULL;
+ } else
+ memset(sc->sc_indir_data, 0, sc->sc_clsize);
+
+ return &sc->sc_indir_data[ioff];
+}
+
+/*
+ * The kernel thread (one for every active snapshot).
+ *
+ * After wakeup it cleans the cache and runs the I/O requests.
+ */
+static void
+fss_bs_thread(void *arg)
+{
+ int error, len, nfreed, nio, s;
+ long off;
+ caddr_t addr;
+ u_int32_t c, cl, ch, *indirp;
+ struct buf *bp, *nbp;
+ struct fss_softc *sc;
+ struct fss_cache *scp, *scl;
+
+ sc = arg;
+
+ scl = sc->sc_cache+sc->sc_cache_size;
+
+ s = splbio();
+ nbp = pool_get(&bufpool, PR_WAITOK);
+ splx(s);
+
+ nfreed = nio = 1; /* Dont sleep the first time */
+
+ for (;;) {
+ if (nfreed == 0 && nio == 0)
+ tsleep(&sc->sc_bs_proc, PVM, "fssbs", 0);
+ if ((sc->sc_flags & FSS_BS_THREAD) == 0) {
+ s = splbio();
+ pool_put(&bufpool, nbp);
+ splx(s);
+#ifdef FSS_STATISTICS
+ printf("fss%d: cow called %" PRId64 " times,"
+ " copied %" PRId64 " clusters,"
+ " cache full %" PRId64 " times\n",
+ sc->sc_unit,
+ FSS_STAT_VAL(sc, cow_calls),
+ FSS_STAT_VAL(sc, cow_copied),
+ FSS_STAT_VAL(sc, cow_cache_full));
+ printf("fss%d: %" PRId64 " indir reads,"
+ " %" PRId64 " indir writes\n",
+ sc->sc_unit,
+ FSS_STAT_VAL(sc, indir_read),
+ FSS_STAT_VAL(sc, indir_write));
+#endif /* FSS_STATISTICS */
+ sc->sc_bs_proc = NULL;
+ kthread_exit(0);
+ }
+
+ /*
+ * Clean the cache
+ */
+ nfreed = 0;
+ for (scp = sc->sc_cache; scp < scl; scp++) {
+ if (scp->fc_type != FSS_CACHE_VALID)
+ continue;
+ indirp = fss_bs_indir(sc, scp->fc_cluster);
+ if (indirp != NULL) {
+ error = fss_write_cluster(scp, sc->sc_clnext);
+ } else
+ error = EIO;
+
+ if (error == 0) {
+ *indirp = sc->sc_clnext++;
+ sc->sc_indir_dirty = 1;
+ } else
+ fss_error(sc, "write bs error %d", error);
+
+ scp->fc_type = FSS_CACHE_FREE;
+ nfreed++;
+ wakeup(&scp->fc_type);
+ }
+ if (nfreed)
+ wakeup(&sc->sc_cache);
+
+ /*
+ * Process I/O requests
+ */
+ nio = 0;
+
+ if ((bp = BUFQ_GET(&sc->sc_bufq)) == NULL)
+ continue;
+
+ nio++;
+
+ if (!fss_valid(sc)) {
+ bp->b_error = ENXIO;
+ bp->b_flags |= B_ERROR;
+ bp->b_resid = bp->b_bcount;
+ biodone(bp);
+ continue;
+ }
+
+ /*
+ * First read from the snapshotted block device.
+ * XXX Split to only read those parts that have not
+ * been saved to backing store?
+ */
+ BUF_INIT(nbp);
+ nbp->b_flags = B_READ;
+ nbp->b_bcount = bp->b_bcount;
+ nbp->b_bufsize = bp->b_bcount;
+ nbp->b_error = 0;
+ nbp->b_data = bp->b_data;
+ nbp->b_blkno = nbp->b_rawblkno = bp->b_blkno;
+ nbp->b_proc = bp->b_proc;
+ nbp->b_dev = sc->sc_bdev;
+ nbp->b_vp = NULLVP;
+
+ (*sc->sc_strategy)(nbp);
+
+ if (biowait(nbp) != 0) {
+ bp->b_resid = bp->b_bcount;
+ bp->b_error = nbp->b_error;
+ bp->b_flags |= B_ERROR;
+ biodone(bp);
+ continue;
+ }
+
+ block_to_cluster(sc, bp->b_blkno, 0, &cl, &off);
+ block_to_cluster(sc, bp->b_blkno, bp->b_bcount-1, &ch, NULL);
+ bp->b_resid = bp->b_bcount;
+ addr = bp->b_data;
+
+ /*
+ * Replace those parts that have been saved to backing store.
+ */
+ for (c = cl; c <= ch;
+ c++, off = 0, bp->b_resid -= len, addr += len) {
+ len = sc->sc_clsize-off;
+ if (len > bp->b_resid)
+ len = bp->b_resid;
+
+ if (isclr(sc->sc_copied, c))
+ continue;
+
+ indirp = fss_bs_indir(sc, c);
+ if (indirp == NULL || *indirp == 0) {
+ /*
+ * Not on backing store. Either in cache
+ * or hole in the snapshotted block device.
+ */
+ for (scp = sc->sc_cache; scp < scl; scp++)
+ if (scp->fc_type == FSS_CACHE_VALID &&
+ scp->fc_cluster == c)
+ break;
+ if (scp < scl)
+ memcpy(addr, scp->fc_data+off, len);
+ else
+ memset(addr, 0, len);
+ continue;
+ }
+ /*
+ * Read from backing store.
+ */
+ if ((error = fss_bs_io(sc, FSS_READ, *indirp,
+ off, len, addr)) != 0) {
+ bp->b_resid = bp->b_bcount;
+ bp->b_error = error;
+ bp->b_flags |= B_ERROR;
+ break;
+ }
+ }
+
+ biodone(bp);
+ }
+}
diff --git a/sys/dev/fssvar.h b/sys/dev/fssvar.h
new file mode 100644
index 00000000000..c8a2eb61438
--- /dev/null
+++ b/sys/dev/fssvar.h
@@ -0,0 +1,163 @@
+/* $NetBSD: fssvar.h,v 1.1 2003/12/10 11:40:11 hannken Exp $ */
+
+/*-
+ * Copyright (c) 2003 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Juergen Hannken-Illjes.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the NetBSD
+ * Foundation, Inc. and its contributors.
+ * 4. Neither the name of The NetBSD Foundation nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _SYS_DEV_FSSVAR_H
+#define _SYS_DEV_FSSVAR_H
+
+struct fss_set {
+ char *fss_mount; /* Mount point of file system */
+ char *fss_bstore; /* Path of backing store */
+ blksize_t fss_csize; /* Preferred cluster size */
+};
+
+struct fss_get {
+ char fsg_mount[MNAMELEN]; /* Mount point of file system */
+ struct timeval fsg_time; /* Time this snapshot was taken */
+ blksize_t fsg_csize; /* Current cluster size */
+ blkcnt_t fsg_mount_size; /* # clusters on file system */
+ blkcnt_t fsg_bs_size; /* # clusters on backing store */
+};
+
+#define FSSIOCSET _IOW('F', 0, struct fss_set) /* Configure */
+#define FSSIOCGET _IOR('F', 1, struct fss_get) /* Status */
+#define FSSIOCCLR _IO('F', 2) /* Unconfigure */
+
+#ifdef _KERNEL
+
+#define FSS_CLUSTER_MAX (1<<24) /* Upper bound of clusters. The
+ sc_copied map uses
+ FSS_CLUSTER_MAX/NBBY bytes */
+typedef enum {
+ FSS_CACHE_FREE = 0, /* Cache entry is free */
+ FSS_CACHE_BUSY = 1, /* Cache entry is read from device */
+ FSS_CACHE_VALID = 2 /* Cache entry contains valid data */
+} fss_cache_type;
+
+struct fss_cache {
+ fss_cache_type fc_type; /* Current state */
+ struct fss_softc *fc_softc; /* Backlink to our softc */
+ volatile int fc_xfercount; /* Number of outstanding transfers */
+ u_int32_t fc_cluster; /* Cluster number of this entry */
+ caddr_t fc_data; /* Data */
+};
+
+struct fss_softc {
+ int sc_unit; /* Logical unit number */
+ struct lock sc_lock; /* Get exclusive access to device */
+ volatile int sc_flags; /* Flags */
+#define FSS_ACTIVE 0x01 /* Snapshot is active */
+#define FSS_ERROR 0x02 /* I/o error occured */
+#define FSS_BS_THREAD 0x04 /* Kernel thread is running */
+ struct mount *sc_mount; /* Mount point */
+ char sc_mntname[MNAMELEN]; /* Mount point */
+ struct timeval sc_time; /* Time this snapshot was taken */
+ dev_t sc_bdev; /* Underlying block device */
+ void (*sc_strategy)(struct buf *); /* And its strategy */
+ struct vnode *sc_bs_vp; /* Our backing store */
+ int sc_bs_bsize; /* Its bsize */
+ struct proc *sc_bs_proc; /* Our kernel thread */
+ u_int32_t sc_clsize; /* Size of cluster */
+ u_int32_t sc_clcount; /* # clusters in file system */
+ u_int8_t *sc_copied; /* Map of clusters already copied */
+ long sc_cllast; /* Bytes in last cluster */
+ int sc_cowcount; /* Number of cow in progress */
+ int sc_cache_size; /* Number of entries in sc_cache */
+ struct fss_cache *sc_cache; /* Cluster cache */
+ struct bufq_state sc_bufq; /* Transfer queue */
+ u_int32_t sc_clnext; /* Next free cluster on backing store */
+ int sc_indir_size; /* # clusters for indirect mapping */
+ u_int8_t *sc_indir_valid; /* Map of valid indirect clusters */
+ u_int32_t sc_indir_cur; /* Current indir cluster number */
+ int sc_indir_dirty; /* Current indir cluster modified */
+ u_int32_t *sc_indir_data; /* Current indir cluster data */
+};
+
+struct fss_softc fss_softc[NFSS];
+
+void fss_copy_on_write(struct fss_softc *, struct buf *);
+int fss_umount_hook(struct mount *, int);
+
+/*
+ * Get this dev's softc if it is a valid device.
+ * Return a pointer to its softc.
+ */
+static inline int
+fss_dev_to_softc(dev_t dev, struct fss_softc **scp)
+{
+ int unit;
+ struct fss_softc *sc;
+
+ unit = minor(dev);
+ if (unit < 0 || unit >= NFSS)
+ return ENODEV;
+ sc = &fss_softc[unit];
+ *scp = sc;
+
+ return 0;
+}
+
+/*
+ * Check if this buf needs to be copied on write.
+ * Unroll the loop for small NFSS.
+ */
+static inline void
+fss_cow_hook(struct buf *bp)
+{
+ int i;
+
+ if (bp->b_flags & B_READ)
+ return;
+
+ if (NFSS <= 4) {
+ if (__predict_false(fss_softc[0].sc_bdev == bp->b_dev ||
+ (NFSS > 1 && fss_softc[1].sc_bdev == bp->b_dev) ||
+ (NFSS > 2 && fss_softc[2].sc_bdev == bp->b_dev) ||
+ (NFSS > 3 && fss_softc[3].sc_bdev == bp->b_dev)))
+ for (i = 0; i < NFSS; i++)
+ if (fss_softc[i].sc_bdev == bp->b_dev)
+ fss_copy_on_write(&fss_softc[i], bp);
+ } else {
+ for (i = 0; i < NFSS; i++)
+ if (__predict_false(fss_softc[i].sc_bdev == bp->b_dev))
+ fss_copy_on_write(&fss_softc[i], bp);
+ }
+}
+
+#endif /* _KERNEL */
+
+#endif /* !_SYS_DEV_FSSVAR_H */