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libbe(3): Add a serial to the generated snapshot names

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To use bectl in an example, when one creates a new boot environment with
either `bectl create <be>` or `bectl create -e <otherbe> <be>`, libbe will
take a snapshot of the original boot environment to clone. Previously, this
used %F-%T date format as the snapshot name, but this has some limitations-
attempting to create multiple boot environments in quick succession may
collide if done within the same second.

Tack a serial onto it to reduce the chances of a collision... we could still
collide if multiple processes/threads are creating boot environments at the
same time, but this is likely not a big concern as this has only been
reported as occurring in freebsd-ci setup.

MFC after:	3 days
This commit is contained in:
Kyle Evans 2019-04-03 17:04:38 +00:00
parent c973ee9e06
commit 90cf61e8a5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=345848
1 changed files with 26 additions and 6 deletions
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32
lib/libbe/be.c
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@ -56,6 +56,9 @@ static int be_create_child_noent(libbe_handle_t *lbh, const char *active,
static int be_create_child_cloned(libbe_handle_t *lbh, const char *active);
#endif
/* Arbitrary... should tune */
#define BE_SNAP_SERIAL_MAX 1024
/*
* Iterator function for locating the rootfs amongst the children of the
* zfs_be_root set by loader(8). data is expected to be a libbe_handle_t *.
@ -320,13 +323,32 @@ be_destroy(libbe_handle_t *lbh, const char *name, int options)
options & ~BE_DESTROY_ORIGIN));
}
static void
be_setup_snapshot_name(libbe_handle_t *lbh, char *buf, size_t buflen)
{
time_t rawtime;
int len, serial;
time(&rawtime);
len = strlen(buf);
len += strftime(buf + len, buflen - len, "@%F-%T", localtime(&rawtime));
/* No room for serial... caller will do its best */
if (buflen - len < 2)
return;
for (serial = 0; serial < BE_SNAP_SERIAL_MAX; ++serial) {
snprintf(buf + len, buflen - len, "-%d", serial);
if (!zfs_dataset_exists(lbh->lzh, buf, ZFS_TYPE_SNAPSHOT))
return;
}
}
int
be_snapshot(libbe_handle_t *lbh, const char *source, const char *snap_name,
bool recursive, char *result)
{
char buf[BE_MAXPATHLEN];
time_t rawtime;
int len, err;
int err;
be_root_concat(lbh, source, buf);
@ -344,10 +366,8 @@ be_snapshot(libbe_handle_t *lbh, const char *source, const char *snap_name,
snprintf(result, BE_MAXPATHLEN, "%s@%s", source,
snap_name);
} else {
time(&rawtime);
len = strlen(buf);
strftime(buf + len, sizeof(buf) - len,
"@%F-%T", localtime(&rawtime));
be_setup_snapshot_name(lbh, buf, sizeof(buf));
if (result != NULL && strlcpy(result, strrchr(buf, '/') + 1,
sizeof(buf)) >= sizeof(buf))
return (set_error(lbh, BE_ERR_INVALIDNAME));