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dissect-image: prefer PARTN= uevent property over "partition" sysfs attr

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The kernel will send us a PARTN= uevent proprty with partition add
events, let's use it instead of going for the "partition" sysfs attr.
It's less racy that way and there are reports the sysfs attr shows up
after the device, which makes it evern worse.
This commit is contained in:
Lennart Poettering 2021-04-22 11:31:14 +02:00
parent eb34cce178
commit c1737506f3
1 changed files with 13 additions and 2 deletions
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15
src/shared/dissect-image.c
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@ -139,7 +139,11 @@ static int enumerator_for_parent(sd_device *d, sd_device_enumerator **ret) {
return 0;
}
static int device_is_partition(sd_device *d, sd_device *expected_parent, blkid_partition pp) {
static int device_is_partition(
sd_device *d,
sd_device *expected_parent,
blkid_partition pp) {
const char *v, *parent_syspath, *expected_parent_syspath;
blkid_loff_t bsize, bstart;
uint64_t size, start;
@ -174,9 +178,16 @@ static int device_is_partition(sd_device *d, sd_device *expected_parent, blkid_p
if (!path_equal(parent_syspath, expected_parent_syspath))
return false; /* Has a different parent than what we need, not interesting to us */
r = sd_device_get_sysattr_value(d, "partition", &v);
/* On kernel uevents the partition number we may find in the PARTN= field. Let's use that preferably,
* since it's cheaper and more importantly: the sysfs attribute "partition" appear to become
* available late, hence let's use the property instead, which is available at the moment we see the
* uevent. */
r = sd_device_get_property_value(d, "PARTN", &v);
if (r == -ENOENT)
r = sd_device_get_sysattr_value(d, "partition", &v);
if (r < 0)
return r;
r = safe_atoi(v, &partno);
if (r < 0)
return r;