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Merge pull request #33028 from yuwata/blockdev-util

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blockdev-util: also check loop/partscan sysattr
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Luca Boccassi 2024-05-27 12:44:38 +02:00 committed by GitHub
parent cafe40ec82 bab8c851da
commit 86b89c7309
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1 changed files with 43 additions and 15 deletions
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58
src/shared/blockdev-util.c
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@ -369,19 +369,43 @@ int blockdev_partscan_enabled(int fd) {
* is 1, which can be check with 'ext_range' sysfs attribute. Explicit flag ('GENHD_FL_NO_PART_SCAN')
* can be obtained from 'capability' sysattr.
*
* With https://github.com/torvalds/linux/commit/1ebe2e5f9d68e94c524aba876f27b945669a7879 (v5.17), we
* can check the flag from 'ext_range' sysfs attribute directly.
* With https://github.com/torvalds/linux/commit/46e7eac647b34ed4106a8262f8bedbb90801fadd (v5.17),
* the flag is renamed to GENHD_FL_NO_PART.
*
* With https://github.com/torvalds/linux/commit/1ebe2e5f9d68e94c524aba876f27b945669a7879 (v5.17),
* we can check the flag from 'ext_range' sysfs attribute directly.
*
* With https://github.com/torvalds/linux/commit/430cc5d3ab4d0ba0bd011cfbb0035e46ba92920c (v5.17),
* the value of GENHD_FL_NO_PART is changed from 0x0200 to 0x0004. 💣💣💣
* Note, the new value was used by the GENHD_FL_MEDIA_CHANGE_NOTIFY flag, which was introduced by
* 86ce18d7b7925bfd6b64c061828ca2a857ee83b8 (v2.6.22), and removed by
* 9243c6f3e012a92dd900d97ef45efaf8a8edc448 (v5.7). If we believe the commit message of
* e81cd5a983bb35dabd38ee472cf3fea1c63e0f23, the flag was never used. So, fortunately, we can use
* both the new and old values safely.
*
* With https://github.com/torvalds/linux/commit/b9684a71fca793213378dd410cd11675d973eaa1 (v5.19),
* another flag GD_SUPPRESS_PART_SCAN is introduced for loopback block device, and partition scanning
* is done only when both GENHD_FL_NO_PART and GD_SUPPRESS_PART_SCAN are not set. Before the commit,
* LO_FLAGS_PARTSCAN flag was directly tied with GENHD_FL_NO_PART. But with this change now it is
* tied with GD_SUPPRESS_PART_SCAN. So, LO_FLAGS_PARTSCAN cannot be obtained from 'ext_range'
* sysattr, which corresponds to GENHD_FL_NO_PART, and we need to read 'loop/partscan'. 💣💣💣
*
* With https://github.com/torvalds/linux/commit/73a166d9749230d598320fdae3b687cdc0e2e205 (v6.3),
* the GD_SUPPRESS_PART_SCAN flag is also introduced for userspace block device (ublk). Though, not
* sure if we should support the device...
*
* With https://github.com/torvalds/linux/commit/e81cd5a983bb35dabd38ee472cf3fea1c63e0f23 (v6.3),
* the 'capability' sysfs attribute is deprecated, hence we cannot check the flag from it.
* the 'capability' sysfs attribute is deprecated, hence we cannot check flags from it. 💣💣💣
*
* With https://github.com/torvalds/linux/commit/a4217c6740dc64a3eb6815868a9260825e8c68c6
* (backported to v6.9), the partscan status is directly exposed as 'partscan' sysattr.
* With https://github.com/torvalds/linux/commit/a4217c6740dc64a3eb6815868a9260825e8c68c6 (v6.10,
* backported to v6.9), the partscan status is directly exposed as 'partscan' sysattr.
*
* To support both old and new kernels, we need to do the following: first check 'partscan' attr
* where the information is made directly available; then, fall back to 'ext_range' sysfs attribute,
* and if '1' we can conclude partition scanning is disabled; otherwise check 'capability' sysattr
* for ancient version. */
* To support both old and new kernels, we need to do the following:
* 1) check 'partscan' sysfs attribute where the information is made directly available,
* 2) check 'loop/partscan' sysfs attribute for loopback block devices, and if '0' we can conclude
* partition scanning is disabled,
* 3) check 'ext_range' sysfs attribute, and if '1' we can conclude partition scanning is disabled,
* 4) otherwise check 'capability' sysfs attribute for ancient version. */
assert(fd >= 0);
@ -389,10 +413,16 @@ int blockdev_partscan_enabled(int fd) {
if (r < 0)
return r;
/* For v6.10 or newer. */
r = device_get_sysattr_bool(dev, "partscan");
if (r != -ENOENT)
return r;
/* For loopback block device, especially for v5.19 or newer. Even if this is enabled, we also need to
* check GENHD_FL_NO_PART flag through 'ext_range' and 'capability' sysfs attributes below. */
if (device_get_sysattr_bool(dev, "loop/partscan") == 0)
return false;
r = device_get_sysattr_int(dev, "ext_range", &ext_range);
if (r == -ENOENT) /* If the ext_range file doesn't exist then we are most likely looking at a
* partition block device, not the whole block device. And that means we have no
@ -412,12 +442,10 @@ int blockdev_partscan_enabled(int fd) {
if (r < 0)
return r;
#ifndef GENHD_FL_NO_PART_SCAN
#define GENHD_FL_NO_PART_SCAN (0x0200)
#endif
/* If 0x200 is set, part scanning is definitely off. */
if (FLAGS_SET(capability, GENHD_FL_NO_PART_SCAN))
#define GENHD_FL_NO_PART_OLD 0x0200
#define GENHD_FL_NO_PART_NEW 0x0004
/* If one of the NO_PART flags is set, part scanning is definitely off. */
if ((capability & (GENHD_FL_NO_PART_OLD | GENHD_FL_NO_PART_NEW)) != 0)
return false;
/* Otherwise, assume part scanning is on, we have no further checks available. Assume the best. */