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Wed, 7 Feb 2024 09:24:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id fqlID2VMw2UQTwAAD6G6ig (envelope-from ); Wed, 07 Feb 2024 09:24:53 +0000 Date: Wed, 7 Feb 2024 10:24:23 +0100 From: David Sterba To: Anand Jain Cc: David Sterba , linux-btrfs@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] btrfs: always scan a single device when mounted Message-ID: <20240207092423.GS355@twin.jikos.cz> Reply-To: dsterba@suse.cz References: <20240205174340.30327-1-dsterba@suse.com> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Authentication-Results: smtp-out2.suse.de; none X-Spamd-Result: default: False [-2.80 / 50.00]; ARC_NA(0.00)[]; HAS_REPLYTO(0.30)[dsterba@suse.cz]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; REPLYTO_ADDR_EQ_FROM(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] X-Spam-Level: X-Spam-Flag: NO X-Spam-Score: -2.80 On Wed, Feb 07, 2024 at 10:44:22AM +0530, Anand Jain wrote: > > > On 2/5/24 23:13, David Sterba wrote: > > 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. > > It's reasonable. However is there any logs from the debug message to > confirm? > > > > 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. > > And at the same time, if the device is not mounted, it still does > not register the single device. As in the original design. > > > 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. > > > > It looks like the logic in find_fsid_by_device() does not verify if the > %fsid_fs_devices and %devt_fs_devices are the same. I am concerned that > if they aren't, and %devt_fs_devices is matched by devt only, it implies > that the rest of the populated values in fs_devices may be inconsistent > (from the super). And this actually a problem, a lot of fstests fail with messages like: btrfs/004 [22:53:33][ 346.883630] run fstests btrfs/004 at 2024-02-06 22:53:34 [ 347.513164] BTRFS: device fsid e161b391-e959-419b-b6a6-9c1a371a6c15 devid 1 transid 11 /dev/vda scanned by mount (30014) [ 347.515665] BTRFS info (device vda): first mount of filesystem e161b391-e959-419b-b6a6-9c1a371a6c15 [ 347.516597] BTRFS info (device vda): using crc32c (crc32c-generic) checksum algorithm [ 347.517716] BTRFS info (device vda): using free-space-tree [ 347.996843] BTRFS: device fsid d9f25a27-92c4-4ff3-a2da-634546711e68 devid 1 transid 6 /dev/vdb skip registration scanned by mkfs.btrfs (30078) [ 348.009943] BTRFS: device fsid d9f25a27-92c4-4ff3-a2da-634546711e68 devid 1 transid 6 /dev/vdb scanned by mount (30082) [ 348.013764] BTRFS info (device vdb): first mount of filesystem d9f25a27-92c4-4ff3-a2da-634546711e68 [ 348.014943] BTRFS info (device vdb): using crc32c (crc32c-generic) checksum algorithm [ 348.015949] BTRFS error (device vdb): superblock fsid doesn't match fsid of fs_devices: d9f25a27-92c4-4ff3-a2da-634546711e68 != 3fb9009e-b1d5-46ac-ba94-8120384610e4 [ 348.017653] BTRFS error (device vdb): superblock metadata_uuid doesn't match metadata uuid of fs_devices: d9f25a27-92c4-4ff3-a2da-634546711e68 != 3fb9009e-b1d5-46ac-ba94-8120384610e4 this [ 348.019590] BTRFS error (device vdb): dev_item UUID does not match metadata fsid: 3fb9009e-b1d5-46ac-ba94-8120384610e4 != d9f25a27-92c4-4ff3-a2da-634546711e68 [ 348.021313] BTRFS error (device vdb): superblock contains fatal errors [ 348.022263] BTRFS error (device vdb): open_ctree failed [failed, exit status 1][ 348.058344] BTRFS info (device vda): last unmount of filesystem e161b391-e959-419b-b6a6-9c1a371a6c15 and there are messages about using temp-fsid feature but that's not what I'd expect, apparently the uuids get totally mixed up: btrfs/002 [22:52:24][ 276.908253] run fstests btrfs/002 at 2024-02-06 22:52:24 [ 277.531910] BTRFS: device fsid e161b391-e959-419b-b6a6-9c1a371a6c15 devid 1 transid 9 /dev/vda scanned by mount (15065) [ 277.534162] BTRFS info (device vda): first mount of filesystem e161b391-e959-419b-b6a6-9c1a371a6c15 [ 277.535108] BTRFS info (device vda): using crc32c (crc32c-generic) checksum algorithm [ 277.535913] BTRFS info (device vda): using free-space-tree [ 277.782925] BTRFS: device fsid c69cb0c6-6ca1-4e07-9e4e-c5b5cc09b2c9 devid 1 transid 6 /dev/vdb skip registration scanned by mkfs.btrfs (15109) [ 277.824885] BTRFS: device /dev/vdb using temp-fsid d1299d0e-92d4-47a5-b6e7-5f998f86c5f0 [ 277.827699] BTRFS: device fsid c69cb0c6-6ca1-4e07-9e4e-c5b5cc09b2c9 devid 1 transid 6 /dev/vdb scanned by mount (15117) [ 277.830983] BTRFS info (device vdb): first mount of filesystem c69cb0c6-6ca1-4e07-9e4e-c5b5cc09b2c9 [ 277.832252] BTRFS info (device vdb): using crc32c (crc32c-generic) checksum algorithm [ 277.833325] BTRFS info (device vdb): using free-space-tree [ 277.847045] BTRFS info (device vdb): checking UUID tree [ 294.727566] grep (19725) used greatest stack depth: 24816 bytes left [ 294.788244] dd (19697) used greatest stack depth: 24544 bytes left [ 295.631873] dd (19752) used greatest stack depth: 24328 bytes left [ 317.755256] BTRFS info (device vdb): last unmount of filesystem d1299d0e-92d4-47a5-b6e7-5f998f86c5f0 [ 317.820227] BTRFS info (device vda): last unmount of filesystem e161b391-e959-419b-b6a6-9c1a371a6c15 > I had a bunch of test cases for temp-fsid, I need to (find them) and > send it out. > > > As the main part of device scanning and list update is done in > > device_list_add() that handles all corner cases and locking, it is > > extended to take a parameter that tells it to do everything as before, > > except adding a new device entry. > > Hm. %new_device_added was for btrfs_scan_one_device() so that it can > call btrfs_free_stale_devices(), removing any stale devices if present. > However, theoretically, there shouldn't be any stale devices. Let's keep > it for now, as the find_fsid_by_device() logic might return incorrect > fs_devices (I need to confirm this again). Ok, that's a reasonable idea. > > 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 is 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 rescan" it will change as it triggers the > > "btrfs device scan" > > > rename. > > > > The fix was verified by users whose systems were affected. > > > > CC: stable@vger.kernel.org # 6.7+ > > Fixes: bc27d6f0aa0e ("btrfs: scan but don't register device on single device filesystem") > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=218353 > > Link: https://lore.kernel.org/lkml/CAKLYgeJ1tUuqLcsquwuFqjDXPSJpEiokrWK2gisPKDZLs8Y2TQ@mail.gmail.com/ > > Signed-off-by: David Sterba > > --- > > fs/btrfs/volumes.c | 30 ++++++++++++++---------------- > > 1 file changed, 14 insertions(+), 16 deletions(-) > > > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > > index 474ab7ed65ea..f2c2f7ca5c3d 100644 > > --- a/fs/btrfs/volumes.c > > +++ b/fs/btrfs/volumes.c > > @@ -738,6 +738,7 @@ static noinline struct btrfs_device *device_list_add(const char *path, > > bool same_fsid_diff_dev = false; > > bool has_metadata_uuid = (btrfs_super_incompat_flags(disk_super) & > > BTRFS_FEATURE_INCOMPAT_METADATA_UUID); > > > > + bool can_create_new = *new_device_added; > > > > > > if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_CHANGING_FSID_V2) { > > btrfs_err(NULL, > > @@ -753,6 +754,7 @@ static noinline struct btrfs_device *device_list_add(const char *path, > > return ERR_PTR(error); > > } > > > > > > + *new_device_added = false; > > > > > fs_devices = find_fsid_by_device(disk_super, path_devt, &same_fsid_diff_dev); > > > > if (!fs_devices) { > > @@ -804,6 +806,15 @@ static noinline struct btrfs_device *device_list_add(const char *path, > > return ERR_PTR(-EBUSY); > > } > > > > + if (!can_create_new) { > > > > > + pr_info( > > + "BTRFS: device fsid %pU devid %llu transid %llu %s skip registration scanned by %s (%d)\n", > > + disk_super->fsid, devid, found_transid, path, > > + current->comm, task_pid_nr(current)); > > + mutex_unlock(&fs_devices->device_list_mutex); > > + return NULL; > > + } > > + > > > I just ran the temp-fsid test cases attached here. Comparing the output > with and without this patch seems to be breaking something in the > temp-fsid feature. I need to further verify. I will convert this test > to fstests. However, in the meantime, it can be used to verify. Yeah, at this state the patch is broken.