[lxc-devel] [PATCH RFC] overlayfs: overlayfs.v22 or higher needs workdir option
KATOH Yasufumi
karma at jazz.email.ne.jp
Tue Oct 21 11:27:39 UTC 2014
Hi,
I made changes.
>>> On Sat, 18 Oct 2014 01:24:55 +0900
in message "Re: [lxc-devel] [PATCH RFC] overlayfs: overlayfs.v22 or higher needs workdir option"
I wrote:
> > > Mostly ok, just a few cmments below. If you like I'll make the
> > > changes as I apply, or you can send a new version.
> > Thanks for your comment! I have some questions.
> Sorry. I did not read your patch:
> https://lists.linuxcontainers.org/pipermail/lxc-devel/2014-October/010687.html
> I will check it and resend this patch.
* I assume that upperdir is "delta0". Is this right?
* This patch can apply after applying the patch:
https://lists.linuxcontainers.org/pipermail/lxc-devel/2014-October/010687.html
* Add some comments.
---
src/lxc/bdev.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 82 insertions(+), 6 deletions(-)
diff --git a/src/lxc/bdev.c b/src/lxc/bdev.c
index 8a819ab..2253a1b 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 +2177,21 @@ 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;
+ if (strlen(lastslash) < 7)
+ 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 +2204,44 @@ 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 +2306,7 @@ 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 +2332,25 @@ 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 ((ret = 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);
@@ -2307,7 +2367,7 @@ 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;
+ char *osrc, *odelta, *nsrc, *ndelta, *work;
int len, ret;
if (!(osrc = strdup(orig->src)))
return -22;
@@ -2331,6 +2391,22 @@ 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.
+ work = strdup(ndelta);
+ if (!work)
+ return -1;
+ strcpy(&work[strlen(work)-6], "olwork");
+ if (mkdir(work, 0755) < 0) {
+ SYSERROR("error: mkdir %s", work);
+ free(work);
+ return -1;
+ }
+ if (am_unpriv() && chown_mapped_root(ndelta, 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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