| Message ID | 20180329103705.13566-5-anand.jain@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 29.03.2018 13:37, Anand Jain wrote: > During the btrfs dev scan make sure that other copies of superblock > contain the same fsid as the primary SB. So that we bring to the > user notice if the superblock has been overwritten. > > mkfs.btrfs -fq /dev/sdc > mkfs.btrfs -fq /dev/sdb > dd if=/dev/sdb of=/dev/sdc count=4K skip=64K seek=64K obs=1 ibs=1 > mount /dev/sdc /btrfs > > Caveat: Pls note that older btrfs-progs do not wipe the non-overwriting > stale superblock like copy2 if a smaller mkfs.btrfs -b <size> is created. > Thus this patch in the kernel will report error. The workaround is to wipe > the superblock manually, like > dd if=/dev/zero of=<dev> seek=274877906944 ibs=1 obs=1 count4K > OR apply the btrfs-progs patch > btrfs-progs: wipe copies of the stale superblock beyond -b size > which shall find and wipe the non overwriting superblock during mkfs. > > Signed-off-by: Anand Jain <anand.jain@oracle.com> > v1->v2: > Do an explicit read for primary superblock. Drop kzalloc(). > Fix split pr_err(). Same thing about the change log as in 2/7. Otherwise : Reviewed-by: Nikolay Borisov <nborisov@suse.com> > --- > fs/btrfs/volumes.c | 48 ++++++++++++++++++++++++++++++++++++++---------- > 1 file changed, 38 insertions(+), 10 deletions(-) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index e63723f23227..035affa447fa 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -1198,39 +1198,67 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr, > int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, > struct btrfs_fs_devices **fs_devices_ret) > { > + struct btrfs_super_block *disk_super_primary; > struct btrfs_super_block *disk_super; > struct btrfs_device *device; > struct block_device *bdev; > + struct page *page_primary; > struct page *page; > int ret = 0; > u64 bytenr; > + int i; > > - /* > - * we would like to check all the supers, but that would make > - * a btrfs mount succeed after a mkfs from a different FS. > - * So, we need to add a special mount option to scan for > - * later supers, using BTRFS_SUPER_MIRROR_MAX instead > - */ > - bytenr = btrfs_sb_offset(0); > flags |= FMODE_EXCL; > > bdev = blkdev_get_by_path(path, flags, holder); > if (IS_ERR(bdev)) > return PTR_ERR(bdev); > > - ret = btrfs_read_disk_super(bdev, bytenr, &page, &disk_super); > + /* > + * We would like to check all the supers and use one good copy, > + * but that would make a btrfs mount succeed after a mkfs from > + * a different FS. > + * So, we need to add a special mount option to scan for > + * later supers, using BTRFS_SUPER_MIRROR_MAX instead. > + * So, just validate if all copies of the superblocks are ok > + * and have the same fsid. > + */ > + bytenr = btrfs_sb_offset(0); > + ret = btrfs_read_disk_super(bdev, bytenr, &page_primary, > + &disk_super_primary); > if (ret < 0) > goto error_bdev_put; > > + for (i = 1; i < BTRFS_SUPER_MIRROR_MAX; i++) { > + bytenr = btrfs_sb_offset(i); > + ret = btrfs_read_disk_super(bdev, bytenr, &page, &disk_super); > + if (ret < 0) { > + ret = 0; > + continue; > + } > + > + if (memcmp(disk_super_primary->fsid, disk_super->fsid, > + BTRFS_FSID_SIZE)) { > + pr_err("BTRFS (device %pg): superblock fsid mismatch, primary %pU copy%d %pU", > + bdev, disk_super_primary->fsid, i, > + disk_super->fsid); > + ret = -EINVAL; > + btrfs_release_disk_super(page); > + goto error_rel_primary; > + } > + btrfs_release_disk_super(page); > + } > + > mutex_lock(&uuid_mutex); > - device = device_list_add(path, disk_super); > + device = device_list_add(path, disk_super_primary); > if (IS_ERR(device)) > ret = PTR_ERR(device); > else > *fs_devices_ret = device->fs_devices; > mutex_unlock(&uuid_mutex); > > - btrfs_release_disk_super(page); > +error_rel_primary: > + btrfs_release_disk_super(page_primary); > > error_bdev_put: > blkdev_put(bdev, flags); > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index e63723f23227..035affa447fa 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1198,39 +1198,67 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr, int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, struct btrfs_fs_devices **fs_devices_ret) { + struct btrfs_super_block *disk_super_primary; struct btrfs_super_block *disk_super; struct btrfs_device *device; struct block_device *bdev; + struct page *page_primary; struct page *page; int ret = 0; u64 bytenr; + int i; - /* - * we would like to check all the supers, but that would make - * a btrfs mount succeed after a mkfs from a different FS. - * So, we need to add a special mount option to scan for - * later supers, using BTRFS_SUPER_MIRROR_MAX instead - */ - bytenr = btrfs_sb_offset(0); flags |= FMODE_EXCL; bdev = blkdev_get_by_path(path, flags, holder); if (IS_ERR(bdev)) return PTR_ERR(bdev); - ret = btrfs_read_disk_super(bdev, bytenr, &page, &disk_super); + /* + * We would like to check all the supers and use one good copy, + * but that would make a btrfs mount succeed after a mkfs from + * a different FS. + * So, we need to add a special mount option to scan for + * later supers, using BTRFS_SUPER_MIRROR_MAX instead. + * So, just validate if all copies of the superblocks are ok + * and have the same fsid. + */ + bytenr = btrfs_sb_offset(0); + ret = btrfs_read_disk_super(bdev, bytenr, &page_primary, + &disk_super_primary); if (ret < 0) goto error_bdev_put; + for (i = 1; i < BTRFS_SUPER_MIRROR_MAX; i++) { + bytenr = btrfs_sb_offset(i); + ret = btrfs_read_disk_super(bdev, bytenr, &page, &disk_super); + if (ret < 0) { + ret = 0; + continue; + } + + if (memcmp(disk_super_primary->fsid, disk_super->fsid, + BTRFS_FSID_SIZE)) { + pr_err("BTRFS (device %pg): superblock fsid mismatch, primary %pU copy%d %pU", + bdev, disk_super_primary->fsid, i, + disk_super->fsid); + ret = -EINVAL; + btrfs_release_disk_super(page); + goto error_rel_primary; + } + btrfs_release_disk_super(page); + } + mutex_lock(&uuid_mutex); - device = device_list_add(path, disk_super); + device = device_list_add(path, disk_super_primary); if (IS_ERR(device)) ret = PTR_ERR(device); else *fs_devices_ret = device->fs_devices; mutex_unlock(&uuid_mutex); - btrfs_release_disk_super(page); +error_rel_primary: + btrfs_release_disk_super(page_primary); error_bdev_put: blkdev_put(bdev, flags);
During the btrfs dev scan make sure that other copies of superblock contain the same fsid as the primary SB. So that we bring to the user notice if the superblock has been overwritten. mkfs.btrfs -fq /dev/sdc mkfs.btrfs -fq /dev/sdb dd if=/dev/sdb of=/dev/sdc count=4K skip=64K seek=64K obs=1 ibs=1 mount /dev/sdc /btrfs Caveat: Pls note that older btrfs-progs do not wipe the non-overwriting stale superblock like copy2 if a smaller mkfs.btrfs -b <size> is created. Thus this patch in the kernel will report error. The workaround is to wipe the superblock manually, like dd if=/dev/zero of=<dev> seek=274877906944 ibs=1 obs=1 count4K OR apply the btrfs-progs patch btrfs-progs: wipe copies of the stale superblock beyond -b size which shall find and wipe the non overwriting superblock during mkfs. Signed-off-by: Anand Jain <anand.jain@oracle.com> v1->v2: Do an explicit read for primary superblock. Drop kzalloc(). Fix split pr_err(). --- fs/btrfs/volumes.c | 48 ++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 38 insertions(+), 10 deletions(-)