[lxc-devel] [PATCH v2] add support for qcow2
Serge Hallyn
serge.hallyn at ubuntu.com
Wed May 14 17:41:20 UTC 2014
Quoting Dwight Engen (dwight.engen at oracle.com):
> On Mon, 12 May 2014 18:02:28 +0000
> Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
>
> > qcow2 backing stores can be attached to a nbd block device using
> > qemu-nbd. This user-space process (pair) stays around for the
> > duration of the device attachment. Obviously we want it to go
> > away when the container shuts down, but not before the filesystems
> > have been cleanly unmounted.
> >
> > The device attachment is done from the task which will become the
> > container monitor before the container setup+init task is spawned.
> > That task starts in a new pid namespace to ensure that the qemu-nbd
> > process will be killed if need be. It sets its parent death signal
> > to sighup, and, on receiving sighup, attempts to do a clean
> > qemu-device detach, then exits. This should ensure that the
> > device is detached if the qemu monitor crashes or exits.
> >
> > It may be worth adding a delay before the qemu-nbd is detached, but
> > my brief tests haven't seen any data corruption.
> >
> > Only the parts required for running a qcow2-backed container are
> > implemented here. Create, destroy, and clone are not. The first
> > use of this that I imagine is for people to use downloaded
> > qcow2-backed images (like ubuntu cloud images, or anything previously
> > used with qemu). I imagine people will want to create/clone/destroy
> > out of band using qemu-img, but if I'm wrong about that we can
> > implement the rest later.
> >
> > Because attach_block_device() is done before the bdev is initialized,
> > and bdev_init needs to know the nbd index so that it can mount the
> > filesystem, we now need to pass the lxc_conf.
> >
> > file_exists() is moved to utils.c so we can use it from bdev.c
> >
> > The nbd attach/detach should lay the groundwork for trivial
> > implementation of qed and raw images.
> >
> > changelog (may 12): qcow: fix idx check at detach
>
> Hey Serge, I had to check the code for how to use this so maybe we
> should document somewhere what the rootfs line needs to look like (ie.
> lxc.rootfs = qcow2:/path/to/diskimg:1).
d'oh. I've intended to do it like that for so long I never even
considered that it wouldn't be obvious. You're right of course.
> Also, I used this against a .vdi image just fine, so maybe we should be
> more generic than just qcow2 and call it qemu? Not sure if qemu-nbd
> supports all the same image formats as qemu-img.
Cool, yes that'd be worth changing. Maybe it even works with raw
as is.
I can't really do that this week, so we can either push this as is
(which you could do now if you ilke) and patch it later to be more
generic, or if you prefer you can update and resend the patch, then I'll
push the new patch.
> For anyone else trying to use this note that I had to:
> 'modprobe nbd max_part=16' or else I would only get the full device node
> (/dev/nbd0) but not the partition nodes (/dev/nbd0p?) which caused lxc
> to hang on startup.
Thanks, yeah I can whip up a documentation patch on monday.
> At any rate, this works great so thanks and:
>
> Acked-by: Dwight Engen <dwight.engen at oracle.com>
>
> > Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
> > ---
> > src/lxc/bdev.c | 296
> > ++++++++++++++++++++++++++++++++++++++++++++++++-
> > src/lxc/bdev.h | 18 ++- src/lxc/conf.c | 3 +-
> > src/lxc/conf.h | 1 +
> > src/lxc/lxccontainer.c | 19 +---
> > src/lxc/start.c | 11 +-
> > src/lxc/utils.c | 7 ++
> > src/lxc/utils.h | 1 +
> > 8 files changed, 333 insertions(+), 23 deletions(-)
> >
> > diff --git a/src/lxc/bdev.c b/src/lxc/bdev.c
> > index 20e9fb3..85b95a7 100644
> > --- a/src/lxc/bdev.c
> > +++ b/src/lxc/bdev.c
> > @@ -41,6 +41,7 @@
> > #include <libgen.h>
> > #include <linux/loop.h>
> > #include <dirent.h>
> > +#include <sys/prctl.h>
> >
> > #include "lxc.h"
> > #include "config.h"
> > @@ -2410,6 +2411,290 @@ static const struct bdev_ops aufs_ops = {
> > .can_snapshot = true,
> > };
> >
> > +//
> > +// qcow2 dev ops
> > +//
> > +
> > +static int qcow2_detect(const char *path)
> > +{
> > + if (strncmp(path, "qcow2:", 6) == 0)
> > + return 1;
> > + return 0;
> > +}
> > +
> > +struct nbd_attach_data {
> > + const char *nbd;
> > + const char *path;
> > +};
> > +
> > +static void nbd_detach(const char *path)
> > +{
> > + int ret;
> > + pid_t pid = fork();
> > +
> > + if (pid < 0) {
> > + SYSERROR("Error forking to detach nbd");
> > + return;
> > + }
> > + if (pid) {
> > + ret = wait_for_pid(pid);
> > + if (ret < 0)
> > + ERROR("nbd disconnect returned an error");
> > + return;
> > + }
> > + execlp("qemu-nbd", "qemu-nbd", "-d", path, NULL);
> > + SYSERROR("Error executing qemu-nbd");
> > + exit(1);
> > +}
> > +
> > +static int do_attach_nbd(void *d)
> > +{
> > + struct nbd_attach_data *data = d;
> > + const char *nbd, *path;
> > + pid_t pid;
> > + sigset_t mask;
> > + int sfd;
> > + ssize_t s;
> > + struct signalfd_siginfo fdsi;
> > +
> > + sigemptyset(&mask);
> > + sigaddset(&mask, SIGHUP);
> > + sigaddset(&mask, SIGCHLD);
> > +
> > + nbd = data->nbd;
> > + path = data->path;
> > +
> > + if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1) {
> > + SYSERROR("Error blocking signals for nbd watcher");
> > + exit(1);
> > + }
> > +
> > + sfd = signalfd(-1, &mask, 0);
> > + if (sfd == -1) {
> > + SYSERROR("Error opening signalfd for nbd task");
> > + exit(1);
> > + }
> > +
> > + if (prctl(PR_SET_PDEATHSIG, SIGHUP, 0, 0, 0) < 0)
> > + SYSERROR("Error setting parent death signal for nbd
> > watcher"); +
> > + pid = fork();
> > + if (pid) {
> > + for (;;) {
> > + s = read(sfd, &fdsi, sizeof(struct
> > signalfd_siginfo));
> > + if (s != sizeof(struct signalfd_siginfo))
> > + SYSERROR("Error reading from
> > signalfd"); +
> > + if (fdsi.ssi_signo == SIGHUP) {
> > + /* container has exited */
> > + nbd_detach(nbd);
> > + exit(0);
> > + } else if (fdsi.ssi_signo == SIGCHLD) {
> > + int status;
> > + while (waitpid(-1, &status, WNOHANG)
> > > 0);
> > + }
> > + }
> > + }
> > +
> > + close(sfd);
> > + if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
> > + WARN("Warning: unblocking signals for nbd watcher");
> > +
> > + execlp("qemu-nbd", "qemu-nbd", "-c", nbd, path, NULL);
> > + SYSERROR("Error executing qemu-nbd");
> > + exit(1);
> > +}
> > +
> > +static bool clone_attach_nbd(const char *nbd, const char *path)
> > +{
> > + pid_t pid;
> > + struct nbd_attach_data data;
> > +
> > + data.nbd = nbd;
> > + data.path = path;
> > +
> > + pid = lxc_clone(do_attach_nbd, &data, CLONE_NEWPID);
> > + if (pid < 0)
> > + return false;
> > + return true;
> > +}
> > +
> > +static bool nbd_busy(int idx)
> > +{
> > + char path[100];
> > + int ret;
> > +
> > + ret = snprintf(path, 100, "/sys/block/nbd%d/pid", idx);
> > + if (ret < 0 || ret >= 100)
> > + return true;
> > + return file_exists(path);
> > +}
> > +
> > +static bool attach_nbd(char *src, struct lxc_conf *conf)
> > +{
> > + char *orig = alloca(strlen(src)+1), *p, path[50];
> > + int i = 0;
> > +
> > + strcpy(orig, src);
> > + /* if path is followed by a partition, drop that for now */
> > + p = strchr(orig, ':');
> > + if (p)
> > + *p = '\0';
> > + while (1) {
> > + sprintf(path, "/dev/nbd%d", i);
> > + if (!file_exists(path))
> > + return false;
> > + if (nbd_busy(i)) {
> > + i++;
> > + continue;
> > + }
> > + if (!clone_attach_nbd(path, orig))
> > + return false;
> > + conf->nbd_idx = i;
> > + return true;
> > + }
> > +}
> > +
> > +static bool requires_nbd(const char *path)
> > +{
> > + if (strncmp(path, "qcow2:", 6) == 0)
> > + return true;
> > + if (strncmp(path, "raw:", 4) == 0)
> > + return true;
> > + return false;
> > +}
> > +
> > +/*
> > + * attach_block_device returns true if all went well,
> > + * meaning either a block device was attached or was not
> > + * needed. It returns false if something went wrong and
> > + * container startup shoudl be stopped.
> > + */
> > +bool attach_block_device(struct lxc_conf *conf)
> > +{
> > + char *path;
> > +
> > + if (!conf->rootfs.path)
> > + return true;
> > + path = conf->rootfs.path;
> > + if (!requires_nbd(path))
> > + return true;
> > + path = strchr(path, ':');
> > + if (!path)
> > + return false;
> > + path++;
> > + if (!attach_nbd(path, conf))
> > + return false;
> > + return true;
> > +}
> > +
> > +void detach_nbd_idx(int idx)
> > +{
> > + int ret;
> > + char path[50];
> > +
> > + ret = snprintf(path, 50, "/dev/nbd%d", idx);
> > + if (ret < 0 || ret >= 50)
> > + return;
> > +
> > + nbd_detach(path);
> > +}
> > +
> > +void detach_block_device(struct lxc_conf *conf)
> > +{
> > + if (conf->nbd_idx != -1)
> > + detach_nbd_idx(conf->nbd_idx);
> > +}
> > +
> > +/*
> > + * Pick the partition # off the end of a qcow2:file:p
> > + * description. Return 1-9 for the partition id, or 0
> > + * for no partition.
> > + */
> > +static int qcow2_get_partition(const char *src)
> > +{
> > + char *p = strchr(src, ':');
> > + if (!p)
> > + return 0;
> > + p = strchr(p+1, ':');
> > + if (!p)
> > + return 0;
> > + p++;
> > + if (*p < '1' && *p > '9')
> > + return 0;
> > + return *p - '0';
> > +}
> > +
> > +static int qcow2_mount(struct bdev *bdev)
> > +{
> > + int ret = -1, partition;
> > + char path[50];
> > +
> > + if (strcmp(bdev->type, "qcow2"))
> > + return -22;
> > + if (!bdev->src || !bdev->dest)
> > + return -22;
> > +
> > + /* nbd_idx should have been copied by bdev_init from the
> > lxc_conf */
> > + if (bdev->nbd_idx < 0)
> > + return -22;
> > + partition = qcow2_get_partition(bdev->src);
> > + if (partition)
> > + ret = snprintf(path, 50, "/dev/nbd%dp%d",
> > bdev->nbd_idx,
> > + partition);
> > + else
> > + ret = snprintf(path, 50, "/dev/nbd%d",
> > bdev->nbd_idx);
> > + if (ret < 0 || ret >= 50) {
> > + ERROR("Error setting up nbd device path");
> > + return ret;
> > + }
> > + ret = mount_unknown_fs(path, bdev->dest, bdev->mntopts);
> > + if (ret < 0)
> > + ERROR("Error mounting %s", bdev->src);
> > +
> > + return ret;
> > +}
> > +
> > +static int qcow2_create(struct bdev *bdev, const char *dest, const
> > char *n,
> > + struct bdev_specs *specs)
> > +{
> > + return -ENOSYS;
> > +}
> > +
> > +/* qcow2 should shine here... */
> > +static int qcow2_clonepaths(struct bdev *orig, struct bdev *new,
> > const char *oldname,
> > + const char *cname, const char *oldpath, const char
> > *lxcpath, int snap,
> > + uint64_t newsize, struct lxc_conf *conf)
> > +{
> > + return -ENOSYS;
> > +}
> > +
> > +static int qcow2_destroy(struct bdev *orig)
> > +{
> > + return -ENOSYS;
> > +}
> > +
> > +static int qcow2_umount(struct bdev *bdev)
> > +{
> > + int ret;
> > +
> > + if (strcmp(bdev->type, "qcow2"))
> > + return -22;
> > + if (!bdev->src || !bdev->dest)
> > + return -22;
> > + ret = umount(bdev->dest);
> > + return ret;
> > +}
> > +
> > +static const struct bdev_ops qcow2_ops = {
> > + .detect = &qcow2_detect,
> > + .mount = &qcow2_mount,
> > + .umount = &qcow2_umount,
> > + .clone_paths = &qcow2_clonepaths,
> > + .destroy = &qcow2_destroy,
> > + .create = &qcow2_create,
> > + .can_snapshot = true,
> > +};
> >
> > static const struct bdev_type bdevs[] = {
> > {.name = "zfs", .ops = &zfs_ops,},
> > @@ -2419,6 +2704,7 @@ static const struct bdev_type bdevs[] = {
> > {.name = "aufs", .ops = &aufs_ops,},
> > {.name = "overlayfs", .ops = &overlayfs_ops,},
> > {.name = "loop", .ops = &loop_ops,},
> > + {.name = "qcow2", .ops = &qcow2_ops,},
> > };
> >
> > static const size_t numbdevs = sizeof(bdevs) / sizeof(struct
> > bdev_type); @@ -2454,7 +2740,7 @@ struct bdev *bdev_get(const char
> > *type) return bdev;
> > }
> >
> > -struct bdev *bdev_init(const char *src, const char *dst, const char
> > *mntopts) +struct bdev *bdev_init(struct lxc_conf *conf, const char
> > *src, const char *dst, const char *mntopts) {
> > int i;
> > struct bdev *bdev;
> > @@ -2480,6 +2766,8 @@ struct bdev *bdev_init(const char *src, const
> > char *dst, const char *mntopts) bdev->src = strdup(src);
> > if (dst)
> > bdev->dest = strdup(dst);
> > + if (strcmp(bdev->type, "qcow2") == 0 || strcmp(bdev->type,
> > "raw") == 0)
> > + bdev->nbd_idx = conf->nbd_idx;
> >
> > return bdev;
> > }
> > @@ -2538,9 +2826,9 @@ static int rsync_rootfs_wrapper(void *data)
> > return rsync_rootfs(arg);
> > }
> >
> > -bool bdev_is_dir(const char *path)
> > +bool bdev_is_dir(struct lxc_conf *conf, const char *path)
> > {
> > - struct bdev *orig = bdev_init(path, NULL, NULL);
> > + struct bdev *orig = bdev_init(conf, path, NULL, NULL);
> > bool ret = false;
> > if (!orig)
> > return ret;
> > @@ -2605,7 +2893,7 @@ struct bdev *bdev_copy(struct lxc_container
> > *c0, const char *cname, return NULL;
> > }
> >
> > - orig = bdev_init(src, NULL, NULL);
> > + orig = bdev_init(c0->lxc_conf, src, NULL, NULL);
> > if (!orig) {
> > ERROR("failed to detect blockdev type for %s", src);
> > return NULL;
> > diff --git a/src/lxc/bdev.h b/src/lxc/bdev.h
> > index cc0bf02..170a530 100644
> > --- a/src/lxc/bdev.h
> > +++ b/src/lxc/bdev.h
> > @@ -24,8 +24,8 @@
> > #ifndef __LXC_BDEV_H
> > #define __LXC_BDEV_H
> > /* blockdev operations for:
> > - * aufs, dir, raw, btrfs, overlayfs, aufs, lvm, loop, zfs
> > - * someday: qemu-nbd, qcow2, qed
> > + * aufs, dir, raw, btrfs, overlayfs, aufs, lvm, loop, zfs, qcow2
> > + * someday: qed
> > */
> >
> > #include "config.h"
> > @@ -83,11 +83,13 @@ struct bdev {
> > // turn the following into a union if need be
> > // lofd is the open fd for the mounted loopback file
> > int lofd;
> > + // index for the connected nbd device
> > + int nbd_idx;
> > };
> >
> > char *overlay_getlower(char *p);
> >
> > -bool bdev_is_dir(const char *path);
> > +bool bdev_is_dir(struct lxc_conf *conf, const char *path);
> >
> > /*
> > * Instantiate a bdev object. The src is used to determine which
> > blockdev @@ -100,7 +102,8 @@ bool bdev_is_dir(const char *path);
> > * use /var/lib/lxc/canonical/rootfs as lower dir,
> > and /var/lib/lxc/c1/delta
> > * as the upper, writeable layer.
> > */
> > -struct bdev *bdev_init(const char *src, const char *dst, const char
> > *data); +struct bdev *bdev_init(struct lxc_conf *conf, const char
> > *src, const char *dst,
> > + const char *data);
> >
> > struct bdev *bdev_copy(struct lxc_container *c0, const char *cname,
> > const char *lxcpath, const char *bdevtype,
> > @@ -110,6 +113,13 @@ struct bdev *bdev_create(const char *dest, const
> > char *type, const char *cname, struct bdev_specs *specs);
> > void bdev_put(struct bdev *bdev);
> >
> > +/*
> > + * these are really for qemu-nbd support, as container shutdown
> > + * must explicitly request device detach.
> > + */
> > +bool attach_block_device(struct lxc_conf *conf);
> > +void detach_block_device(struct lxc_conf *conf);
> > +
> > /* define constants if the kernel/glibc headers don't define them */
> > #ifndef MS_DIRSYNC
> > #define MS_DIRSYNC 128
> > diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> > index 78d9de2..7427a94 100644
> > --- a/src/lxc/conf.c
> > +++ b/src/lxc/conf.c
> > @@ -1555,7 +1555,7 @@ static int setup_rootfs(struct lxc_conf *conf)
> > }
> >
> > // First try mounting rootfs using a bdev
> > - struct bdev *bdev = bdev_init(rootfs->path, rootfs->mount,
> > rootfs->options);
> > + struct bdev *bdev = bdev_init(conf, rootfs->path,
> > rootfs->mount, rootfs->options); if (bdev && bdev->ops->mount(bdev)
> > == 0) { bdev_put(bdev);
> > DEBUG("mounted '%s' on '%s'", rootfs->path,
> > rootfs->mount); @@ -2675,6 +2675,7 @@ struct lxc_conf
> > *lxc_conf_init(void) new->console.slave = -1;
> > new->console.name[0] = '\0';
> > new->maincmd_fd = -1;
> > + new->nbd_idx = -1;
> > new->rootfs.mount = strdup(default_rootfs_mount);
> > if (!new->rootfs.mount) {
> > ERROR("lxc_conf_init : %m");
> > diff --git a/src/lxc/conf.h b/src/lxc/conf.h
> > index 865b87a..3a81d0e 100644
> > --- a/src/lxc/conf.h
> > +++ b/src/lxc/conf.h
> > @@ -334,6 +334,7 @@ struct lxc_conf {
> > int start_delay;
> > int start_order;
> > struct lxc_list groups;
> > + int nbd_idx;
> > };
> >
> > int run_lxc_hooks(const char *name, char *hook, struct lxc_conf
> > *conf, diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> > index 255fde5..fdac433 100644
> > --- a/src/lxc/lxccontainer.c
> > +++ b/src/lxc/lxccontainer.c
> > @@ -82,13 +82,6 @@ return -1;
> >
> > lxc_log_define(lxc_container, lxc);
> >
> > -static bool file_exists(const char *f)
> > -{
> > - struct stat statbuf;
> > -
> > - return stat(f, &statbuf) == 0;
> > -}
> > -
> > static bool config_file_exists(const char *lxcpath, const char
> > *cname) {
> > /* $lxcpath + '/' + $cname + '/config' + \0 */
> > @@ -900,7 +893,7 @@ static bool create_run_template(struct
> > lxc_container *c, char *tpath, bool quiet if (strncmp(src, "aufs:",
> > 5) == 0) src = overlay_getlower(src+5);
> >
> > - bdev = bdev_init(src, c->lxc_conf->rootfs.mount,
> > NULL);
> > + bdev = bdev_init(c->lxc_conf, src,
> > c->lxc_conf->rootfs.mount, NULL); if (!bdev) {
> > ERROR("Error opening rootfs");
> > exit(1);
> > @@ -1992,7 +1985,7 @@ static int do_bdev_destroy(struct lxc_conf
> > *conf) struct bdev *r;
> > int ret = 0;
> >
> > - r = bdev_init(conf->rootfs.path, conf->rootfs.mount, NULL);
> > + r = bdev_init(conf, conf->rootfs.path, conf->rootfs.mount,
> > NULL); if (!r)
> > return -1;
> >
> > @@ -2522,7 +2515,7 @@ static int clone_update_rootfs(struct
> > clone_update_data *data)
> > if (unshare(CLONE_NEWNS) < 0)
> > return -1;
> > - bdev = bdev_init(c->lxc_conf->rootfs.path,
> > c->lxc_conf->rootfs.mount, NULL);
> > + bdev = bdev_init(c->lxc_conf, c->lxc_conf->rootfs.path,
> > c->lxc_conf->rootfs.mount, NULL); if (!bdev)
> > return -1;
> > if (strcmp(bdev->type, "dir") != 0) {
> > @@ -2787,7 +2780,7 @@ static bool lxcapi_rename(struct lxc_container
> > *c, const char *newname) if (!c || !c->name || !c->config_path
> > || !c->lxc_conf) return false;
> >
> > - bdev = bdev_init(c->lxc_conf->rootfs.path,
> > c->lxc_conf->rootfs.mount, NULL);
> > + bdev = bdev_init(c->lxc_conf, c->lxc_conf->rootfs.path,
> > c->lxc_conf->rootfs.mount, NULL); if (!bdev) {
> > ERROR("Failed to find original backing store type");
> > return false;
> > @@ -2880,7 +2873,7 @@ static int lxcapi_snapshot(struct lxc_container
> > *c, const char *commentfile) */
> > flags = LXC_CLONE_SNAPSHOT | LXC_CLONE_KEEPMACADDR |
> > LXC_CLONE_KEEPNAME | LXC_CLONE_KEEPBDEVTYPE |
> > LXC_CLONE_MAYBE_SNAPSHOT;
> > - if (bdev_is_dir(c->lxc_conf->rootfs.path)) {
> > + if (bdev_is_dir(c->lxc_conf, c->lxc_conf->rootfs.path)) {
> > ERROR("Snapshot of directory-backed container
> > requested."); ERROR("Making a copy-clone. If you do want snapshots,
> > then"); ERROR("please create an aufs or overlayfs clone first,
> > snapshot that"); @@ -3082,7 +3075,7 @@ static bool
> > lxcapi_snapshot_restore(struct lxc_container *c, const char *snapnam
> > if (!c || !c->name || !c->config_path) return false;
> >
> > - bdev = bdev_init(c->lxc_conf->rootfs.path,
> > c->lxc_conf->rootfs.mount, NULL);
> > + bdev = bdev_init(c->lxc_conf, c->lxc_conf->rootfs.path,
> > c->lxc_conf->rootfs.mount, NULL); if (!bdev) {
> > ERROR("Failed to find original backing store type");
> > return false;
> > diff --git a/src/lxc/start.c b/src/lxc/start.c
> > index df1304a..a7fb1d3 100644
> > --- a/src/lxc/start.c
> > +++ b/src/lxc/start.c
> > @@ -69,6 +69,7 @@
> > #include "namespace.h"
> > #include "lxcseccomp.h"
> > #include "caps.h"
> > +#include "bdev.h"
> > #include "lsm/lsm.h"
> >
> > lxc_log_define(lxc_start, lxc);
> > @@ -1054,10 +1055,15 @@ int __lxc_start(const char *name, struct
> > lxc_conf *conf, handler->conf->need_utmp_watch = 0;
> > }
> >
> > + if (!attach_block_device(handler->conf)) {
> > + ERROR("Failure attaching block device");
> > + goto out_fini_nonet;
> > + }
> > +
> > err = lxc_spawn(handler);
> > if (err) {
> > ERROR("failed to spawn '%s'", name);
> > - goto out_fini_nonet;
> > + goto out_detach_blockdev;
> > }
> >
> > netnsfd = get_netns_fd(handler->pid);
> > @@ -1110,6 +1116,9 @@ int __lxc_start(const char *name, struct
> > lxc_conf *conf, out_fini:
> > lxc_delete_network(handler);
> >
> > +out_detach_blockdev:
> > + detach_block_device(handler->conf);
> > +
> > out_fini_nonet:
> > lxc_fini(name, handler);
> > return err;
> > diff --git a/src/lxc/utils.c b/src/lxc/utils.c
> > index efec414..b076ce7 100644
> > --- a/src/lxc/utils.c
> > +++ b/src/lxc/utils.c
> > @@ -1306,3 +1306,10 @@ next_loop:
> > free(path);
> > return NULL;
> > }
> > +
> > +bool file_exists(const char *f)
> > +{
> > + struct stat statbuf;
> > +
> > + return stat(f, &statbuf) == 0;
> > +}
> > diff --git a/src/lxc/utils.h b/src/lxc/utils.h
> > index b5e054c..9c618b7 100644
> > --- a/src/lxc/utils.h
> > +++ b/src/lxc/utils.h
> > @@ -280,3 +280,4 @@ uint64_t fnv_64a_buf(void *buf, size_t len,
> > uint64_t hval); int detect_shared_rootfs(void);
> > int detect_ramfs_rootfs(void);
> > char *on_path(char *cmd);
> > +bool file_exists(const char *f);
>
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