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dissect: wait for udev event if verity device not yet available 

The symlink /dev/mapper/dm_name is created by udev after a mapper
device is set up. So libdevmapper/libcrypsetup might tell us that
a verity device exists, but the symlink we use as the source for
the mount operation might not be there yet.
Instead of falling back to a new unique device set up, wait for
the udev event matching on the expected devlink for at least 100ms
(after which the benefits of sharing a device in terms of setup
time start to disappear - on my production machines, opening a new
verity device seems to take between 150ms and 300ms)
This commit is contained in:
Luca Boccassi 2020-08-10 11:19:22 +01:00
parent 030a0d79ff
commit c419b6f0cf
1 changed files with 9 additions and 4 deletions
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13
src/shared/dissect-image.c
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@ -1452,6 +1452,15 @@ static int verity_partition(
if (!IN_SET(r, 0, -ENODEV, -ENOENT))
return log_debug_errno(r, "Checking whether existing verity device %s can be reused failed: %m", node);
if (r == 0) {
/* devmapper might say that the device exists, but the devlink might not yet have been
* created. Check and wait for the udev event in that case. */
r = device_wait_for_devlink(node, "block", 100 * USEC_PER_MSEC, NULL);
/* Fallback to activation with a unique device if it's taking too long */
if (r == -ETIMEDOUT)
break;
if (r < 0)
return r;
if (cd)
crypt_free(cd);
cd = existing_cd;
@ -1461,10 +1470,6 @@ static int verity_partition(
break;
}
/* Sanity check: libdevmapper is known to report that the device already exists and is active,
* but it's actually not there, so the later filesystem probe or mount would fail. */
if (r == 0)
r = access(node, F_OK);
/* An existing verity device was reported by libcryptsetup/libdevmapper, but we can't use it at this time.
* Fall back to activating it with a unique device name. */
if (r != 0 && FLAGS_SET(flags, DISSECT_IMAGE_VERITY_SHARE))