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nspawn: if we set up a loopback device, try to mount it with "discard"

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Let's make sure that our loopback files remain sparse, hence let's set
"discard" as mount option on file systems that support it if the backing device
is a loopback.
This commit is contained in:
Lennart Poettering 2016-10-25 11:39:09 +02:00
parent b5d7f1bbfa
commit 2bce2acce8
1 changed files with 12 additions and 2 deletions
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14
src/nspawn/nspawn.c
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@ -2260,7 +2260,7 @@ static int dissect_image(
static int mount_device(const char *what, const char *where, const char *directory, bool rw) {
#ifdef HAVE_BLKID
_cleanup_blkid_free_probe_ blkid_probe b = NULL;
const char *fstype, *p;
const char *fstype, *p, *options;
int r;
assert(what);
@ -2309,7 +2309,17 @@ static int mount_device(const char *what, const char *where, const char *directo
return -EOPNOTSUPP;
}
return mount_verbose(LOG_ERR, what, p, fstype, MS_NODEV|(rw ? 0 : MS_RDONLY), NULL);
/* If this is a loopback device then let's mount the image with discard, so that the underlying file remains
* sparse when possible. */
if (STR_IN_SET(fstype, "btrfs", "ext4", "vfat", "xfs")) {
const char *l;
l = path_startswith(what, "/dev");
if (l && startswith(l, "loop"))
options = "discard";
}
return mount_verbose(LOG_ERR, what, p, fstype, MS_NODEV|(rw ? 0 : MS_RDONLY), options);
#else
log_error("--image= is not supported, compiled without blkid support.");
return -EOPNOTSUPP;