Pls, ignore this. I need to handle the mapped page in a better way. Thanks, Anand On 03/22/2018 09:01 PM, 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 users 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 Signed-off-by: Anand Jain <anand.j...@oracle.com> --- fs/btrfs/volumes.c | 43 ++++++++++++++++++++++++++++++++----------- 1 file changed, 32 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 87d183accdb2..b79e3ffd2047 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1203,24 +1203,45 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, struct block_device *bdev; struct page *page; int ret = 0; - u64 bytenr; + int i; + u8 fsid_tmp[BTRFS_FSID_SIZE];- /*- * 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);- if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {- ret = -EINVAL; - goto error_bdev_put; + /* + * 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. + */ + for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) { + u64 bytenr = btrfs_sb_offset(i); + + if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) { + if (i != 0) + continue; + ret = -EINVAL; + goto error_bdev_put; + } + if (i == 0) { + memcpy(fsid_tmp, disk_super->fsid, BTRFS_FSID_SIZE); + continue; + } + + if (memcmp(fsid_tmp, disk_super->fsid, BTRFS_FSID_SIZE)) { + pr_err("BTRFS: (device %pg) SB copy#%d fsid %pU "\ + "doesn't match with the primary SB fsid %pU\n", + bdev, i, disk_super->fsid, fsid_tmp); + ret = -EINVAL; + goto error_bdev_put; + } }mutex_lock(&uuid_mutex);
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