[lxc-devel] [PATCH] overlayfs: overlayfs.v22 or higher needs workdir option
Serge Hallyn
serge.hallyn at ubuntu.com
Thu Oct 30 21:28:31 UTC 2014
Quoting KATOH Yasufumi (karma at jazz.email.ne.jp):
> This patch creates workdir as "olwork", and retry mount with workdir
> option when mount is failed.
> It is used to prepare files before atomically swithing with
> destination, and needs to be on the same filesystem as upperdir. It's
> OK for it to be empty.
>
> Signed-off-by: KATOH Yasufumi <karma at jazz.email.ne.jp>
Thanks, looks good.
Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
Now, realistically, since overalyfs_mount() will create the workdir
as needed, I suppose the clone fn doesn't need it... is that right?
(that would simplify some code)
> ---
> src/lxc/bdev.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 89 insertions(+), 7 deletions(-)
>
> diff --git a/src/lxc/bdev.c b/src/lxc/bdev.c
> index 8a819ab..ae5c77c 100644
> --- a/src/lxc/bdev.c
> +++ b/src/lxc/bdev.c
> @@ -2154,10 +2154,12 @@ static int overlayfs_detect(const char *path)
> static int overlayfs_mount(struct bdev *bdev)
> {
> char *options, *dup, *lower, *upper;
> - int len;
> + char *options_work, *work, *lastslash;
> + int lastslashidx;
> + int len, len2;
> unsigned long mntflags;
> char *mntdata;
> - int ret;
> + int ret, ret2;
>
> if (strcmp(bdev->type, "overlayfs"))
> return -22;
> @@ -2175,6 +2177,19 @@ static int overlayfs_mount(struct bdev *bdev)
> *upper = '\0';
> upper++;
>
> + // overlayfs.v22 or higher needs workdir option
> + // if upper is /var/lib/lxc/c2/delta0,
> + // then workdir is /var/lib/lxc/c2/olwork
> + lastslash = strrchr(upper, '/');
> + if (!lastslash)
> + return -22;
> + lastslash++;
> + lastslashidx = lastslash - upper;
> +
> + work = alloca(lastslashidx + 7);
> + strncpy(work, upper, lastslashidx+7);
> + strcpy(work+lastslashidx, "olwork");
> +
> if (parse_mntopts(bdev->mntopts, &mntflags, &mntdata) < 0) {
> free(mntdata);
> return -22;
> @@ -2187,21 +2202,44 @@ static int overlayfs_mount(struct bdev *bdev)
> len = strlen(lower) + strlen(upper) + strlen("upperdir=,lowerdir=,") + strlen(mntdata) + 1;
> options = alloca(len);
> ret = snprintf(options, len, "upperdir=%s,lowerdir=%s,%s", upper, lower, mntdata);
> +
> + len2 = strlen(lower) + strlen(upper) + strlen(work)
> + + strlen("upperdir=,lowerdir=,workdir=") + strlen(mntdata) + 1;
> + options_work = alloca(len2);
> + ret2 = snprintf(options, len2, "upperdir=%s,lowerdir=%s,workdir=%s,%s",
> + upper, lower, work, mntdata);
> }
> else {
> len = strlen(lower) + strlen(upper) + strlen("upperdir=,lowerdir=") + 1;
> options = alloca(len);
> ret = snprintf(options, len, "upperdir=%s,lowerdir=%s", upper, lower);
> +
> + len2 = strlen(lower) + strlen(upper) + strlen(work)
> + + strlen("upperdir=,lowerdir=,workdir=") + 1;
> + options_work = alloca(len2);
> + ret2 = snprintf(options_work, len2, "upperdir=%s,lowerdir=%s,workdir=%s",
> + upper, lower, work);
> }
> - if (ret < 0 || ret >= len) {
> + if (ret < 0 || ret >= len || ret2 < 0 || ret2 >= len2) {
> free(mntdata);
> return -1;
> }
>
> + // mount without workdir option for overlayfs before v21
> ret = mount(lower, bdev->dest, "overlayfs", MS_MGC_VAL | mntflags, options);
> - if (ret < 0)
> - SYSERROR("overlayfs: error mounting %s onto %s options %s",
> + if (ret < 0) {
> + INFO("overlayfs: error mounting %s onto %s options %s. retry with workdir",
> lower, bdev->dest, options);
> +
> + // retry with workdir option for overlayfs v22 and higher
> + ret = mount(lower, bdev->dest, "overlayfs", MS_MGC_VAL | mntflags, options_work);
> + if (ret < 0)
> + SYSERROR("overlayfs: error mounting %s onto %s options %s",
> + lower, bdev->dest, options_work);
> + else
> + INFO("overlayfs: mounted %s onto %s options %s",
> + lower, bdev->dest, options_work);
> + }
> else
> INFO("overlayfs: mounted %s onto %s options %s",
> lower, bdev->dest, options);
> @@ -2266,6 +2304,7 @@ static int overlayfs_clonepaths(struct bdev *orig, struct bdev *new, const char
>
> if (strcmp(orig->type, "dir") == 0) {
> char *delta, *lastslash;
> + char *work;
> int ret, len, lastslashidx;
>
> // if we have /var/lib/lxc/c2/rootfs, then delta will be
> @@ -2291,6 +2330,25 @@ static int overlayfs_clonepaths(struct bdev *orig, struct bdev *new, const char
> if (am_unpriv() && chown_mapped_root(delta, conf) < 0)
> WARN("Failed to update ownership of %s", delta);
>
> + // make workdir for overlayfs.v22 or higher
> + // workdir is /var/lib/lxc/c2/olwork
> + // it is used to prepare files before atomically swithing with destination,
> + // and needs to be on the same filesystem as upperdir,
> + // so it's OK for it to be empty.
> + work = malloc(lastslashidx + 7);
> + if (!work)
> + return -1;
> + strncpy(work, new->dest, lastslashidx+1);
> + strcpy(work+lastslashidx, "olwork");
> + if (mkdir(work, 0755) < 0) {
> + SYSERROR("error: mkdir %s", work);
> + free(work);
> + return -1;
> + }
> + if (am_unpriv() && chown_mapped_root(work, conf) < 0)
> + WARN("Failed to update ownership of %s", work);
> + free(work);
> +
> // the src will be 'overlayfs:lowerdir:upperdir'
> len = strlen(delta) + strlen(orig->src) + 12;
> new->src = malloc(len);
> @@ -2307,8 +2365,9 @@ static int overlayfs_clonepaths(struct bdev *orig, struct bdev *new, const char
> // I think we want to use the original lowerdir, with a
> // private delta which is originally rsynced from the
> // original delta
> - char *osrc, *odelta, *nsrc, *ndelta;
> - int len, ret;
> + char *osrc, *odelta, *nsrc, *ndelta, *work;
> + char *lastslash;
> + int len, ret, lastslashidx;
> if (!(osrc = strdup(orig->src)))
> return -22;
> nsrc = index(osrc, ':') + 1;
> @@ -2331,6 +2390,29 @@ static int overlayfs_clonepaths(struct bdev *orig, struct bdev *new, const char
> }
> if (am_unpriv() && chown_mapped_root(ndelta, conf) < 0)
> WARN("Failed to update ownership of %s", ndelta);
> +
> + // make workdir for overlayfs.v22 or higher
> + // for details, see above.
> + lastslash = strrchr(ndelta, '/');
> + if (!lastslash)
> + return -1;
> + lastslash++;
> + lastslashidx = lastslash - ndelta;
> +
> + work = malloc(lastslashidx + 7);
> + if (!work)
> + return -1;
> + strncpy(work, ndelta, lastslashidx+1);
> + strcpy(work+lastslashidx, "olwork");
> + if ((mkdir(work, 0755) < 0) && errno != EEXIST) {
> + SYSERROR("error: mkdir %s", work);
> + free(work);
> + return -1;
> + }
> + if (am_unpriv() && chown_mapped_root(work, conf) < 0)
> + WARN("Failed to update ownership of %s", work);
> + free(work);
> +
> struct rsync_data_char rdata;
> rdata.src = odelta;
> rdata.dest = ndelta;
> --
> 2.1.1
>
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