--- /dev/null
+From d565fffa68560ac540bf3d62cc79719da50d5e7a Mon Sep 17 00:00:00 2001
+From: Anand Jain <anand.jain@oracle.com>
+Date: Tue, 13 Feb 2024 09:13:56 +0800
+Subject: btrfs: do not skip re-registration for the mounted device
+
+From: Anand Jain <anand.jain@oracle.com>
+
+commit d565fffa68560ac540bf3d62cc79719da50d5e7a upstream.
+
+There are reports that since version 6.7 update-grub fails to find the
+device of the root on systems without initrd and on a single device.
+
+This looks like the device name changed in the output of
+/proc/self/mountinfo:
+
+6.5-rc5 working
+
+ 18 1 0:16 / / rw,noatime - btrfs /dev/sda8 ...
+
+6.7 not working:
+
+ 17 1 0:15 / / rw,noatime - btrfs /dev/root ...
+
+and "update-grub" shows this error:
+
+ /usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?)
+
+This looks like it's related to the device name, but grub-probe
+recognizes the "/dev/root" path and tries to find the underlying device.
+However there's a special case for some filesystems, for btrfs in
+particular.
+
+The generic root device detection heuristic is not done and it all
+relies on reading the device infos by a btrfs specific ioctl. This ioctl
+returns the device name as it was saved at the time of device scan (in
+this case it's /dev/root).
+
+The change in 6.7 for temp_fsid to allow several single device
+filesystem to exist with the same fsid (and transparently generate a new
+UUID at mount time) was to skip caching/registering such devices.
+
+This also skipped mounted device. One step of scanning is to check if
+the device name hasn't changed, and if yes then update the cached value.
+
+This broke the grub-probe as it always read the device /dev/root and
+couldn't find it in the system. A temporary workaround is to create a
+symlink but this does not survive reboot.
+
+The right fix is to allow updating the device path of a mounted
+filesystem even if this is a single device one.
+
+In the fix, check if the device's major:minor number matches with the
+cached device. If they do, then we can allow the scan to happen so that
+device_list_add() can take care of updating the device path. The file
+descriptor remains unchanged.
+
+This does not affect the temp_fsid feature, the UUID of the mounted
+filesystem remains the same and the matching is based on device major:minor
+which is unique per mounted filesystem.
+
+This covers the path when the device (that exists for all mounted
+devices) name changes, updating /dev/root to /dev/sdx. Any other single
+device with filesystem and is not mounted is still skipped.
+
+Note that if a system is booted and initial mount is done on the
+/dev/root device, this will be the cached name of the device. Only after
+the command "btrfs device scan" it will change as it triggers the
+rename.
+
+The fix was verified by users whose systems were affected.
+
+Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=218353
+Link: https://lore.kernel.org/lkml/CAKLYgeJ1tUuqLcsquwuFqjDXPSJpEiokrWK2gisPKDZLs8Y2TQ@mail.gmail.com/
+Fixes: bc27d6f0aa0e ("btrfs: scan but don't register device on single device filesystem")
+CC: stable@vger.kernel.org # 6.7+
+Tested-by: Alex Romosan <aromosan@gmail.com>
+Tested-by: CHECK_1234543212345@protonmail.com
+Signed-off-by: Anand Jain <anand.jain@oracle.com>
+Reviewed-by: David Sterba <dsterba@suse.com>
+Signed-off-by: David Sterba <dsterba@suse.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/btrfs/volumes.c | 57 +++++++++++++++++++++++++++++++++++++++++++----------
+ 1 file changed, 47 insertions(+), 10 deletions(-)
+
+--- a/fs/btrfs/volumes.c
++++ b/fs/btrfs/volumes.c
+@@ -1290,6 +1290,47 @@ int btrfs_forget_devices(dev_t devt)
+ return ret;
+ }
+
++static bool btrfs_skip_registration(struct btrfs_super_block *disk_super,
++ const char *path, dev_t devt,
++ bool mount_arg_dev)
++{
++ struct btrfs_fs_devices *fs_devices;
++
++ /*
++ * Do not skip device registration for mounted devices with matching
++ * maj:min but different paths. Booting without initrd relies on
++ * /dev/root initially, later replaced with the actual root device.
++ * A successful scan ensures grub2-probe selects the correct device.
++ */
++ list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
++ struct btrfs_device *device;
++
++ mutex_lock(&fs_devices->device_list_mutex);
++
++ if (!fs_devices->opened) {
++ mutex_unlock(&fs_devices->device_list_mutex);
++ continue;
++ }
++
++ list_for_each_entry(device, &fs_devices->devices, dev_list) {
++ if (device->bdev && (device->bdev->bd_dev == devt) &&
++ strcmp(device->name->str, path) != 0) {
++ mutex_unlock(&fs_devices->device_list_mutex);
++
++ /* Do not skip registration. */
++ return false;
++ }
++ }
++ mutex_unlock(&fs_devices->device_list_mutex);
++ }
++
++ if (!mount_arg_dev && btrfs_super_num_devices(disk_super) == 1 &&
++ !(btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING))
++ return true;
++
++ return false;
++}
++
+ /*
+ * Look for a btrfs signature on a device. This may be called out of the mount path
+ * and we are not allowed to call set_blocksize during the scan. The superblock
+@@ -1346,18 +1387,14 @@ struct btrfs_device *btrfs_scan_one_devi
+ goto error_bdev_put;
+ }
+
+- if (!mount_arg_dev && btrfs_super_num_devices(disk_super) == 1 &&
+- !(btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING)) {
+- dev_t devt;
++ if (btrfs_skip_registration(disk_super, path, bdev_handle->bdev->bd_dev,
++ mount_arg_dev)) {
++ pr_debug("BTRFS: skip registering single non-seed device %s (%d:%d)\n",
++ path, MAJOR(bdev_handle->bdev->bd_dev),
++ MINOR(bdev_handle->bdev->bd_dev));
+
+- ret = lookup_bdev(path, &devt);
+- if (ret)
+- btrfs_warn(NULL, "lookup bdev failed for path %s: %d",
+- path, ret);
+- else
+- btrfs_free_stale_devices(devt, NULL);
++ btrfs_free_stale_devices(bdev_handle->bdev->bd_dev, NULL);
+
+- pr_debug("BTRFS: skip registering single non-seed device %s\n", path);
+ device = NULL;
+ goto free_disk_super;
+ }
projects / thirdparty / kernel / stable-queue.git / commitdiff
