From ed02363fbbed52a3f5ea0d188edd09045a806eb5 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Mon, 12 Dec 2022 10:19:37 +0800 Subject: btrfs: add extra error messages to cover non-ENOMEM errors from device_add_list() [BUG] When test case btrfs/219 (aka, mount a registered device but with a lower generation) failed, there is not any useful information for the end user to find out what's going wrong. The mount failure just looks like this: # mount -o loop /tmp/219.img2 /mnt/btrfs/ mount: /mnt/btrfs: mount(2) system call failed: File exists. dmesg(1) may have more information after failed mount system call. While the dmesg contains nothing but the loop device change: loop1: detected capacity change from 0 to 524288 [CAUSE] In device_list_add() we have a lot of extra checks to reject invalid cases. That function also contains the regular device scan result like the following prompt: BTRFS: device fsid 6222333e-f9f1-47e6-b306-55ddd4dcaef4 devid 1 transid 8 /dev/loop0 scanned by systemd-udevd (3027) But unfortunately not all errors have their own error messages, thus if we hit something wrong in device_add_list(), there may be no error messages at all. [FIX] Add errors message for all non-ENOMEM errors. For ENOMEM, I'd say we're in a much worse situation, and there should be some OOM messages way before our call sites. CC: stable@vger.kernel.org # 6.0+ Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index aa25fa335d3e..bf0decaac7f3 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -768,8 +768,11 @@ static noinline struct btrfs_device *device_list_add(const char *path, BTRFS_SUPER_FLAG_CHANGING_FSID_V2); error = lookup_bdev(path, &path_devt); - if (error) + if (error) { + btrfs_err(NULL, "failed to lookup block device for path %s: %d", + path, error); return ERR_PTR(error); + } if (fsid_change_in_progress) { if (!has_metadata_uuid) @@ -836,6 +839,9 @@ static noinline struct btrfs_device *device_list_add(const char *path, unsigned int nofs_flag; if (fs_devices->opened) { + btrfs_err(NULL, + "device %s belongs to fsid %pU, and the fs is already mounted", + path, fs_devices->fsid); mutex_unlock(&fs_devices->device_list_mutex); return ERR_PTR(-EBUSY); } @@ -905,6 +911,9 @@ static noinline struct btrfs_device *device_list_add(const char *path, * generation are equal. */ mutex_unlock(&fs_devices->device_list_mutex); + btrfs_err(NULL, +"device %s already registered with a higher generation, found %llu expect %llu", + path, found_transid, device->generation); return ERR_PTR(-EEXIST); } -- cgit v1.2.3