From: Zizhi Wo wozizhi@huawei.com
[ Upstream commit 68415b349f3f16904f006275757f4fcb34b8ee43 ]
I notice a rmap query bug in xfs_io fsmap: [root@fedora ~]# xfs_io -c 'fsmap -vvvv' /mnt EXT: DEV BLOCK-RANGE OWNER FILE-OFFSET AG AG-OFFSET TOTAL 0: 253:16 [0..7]: static fs metadata 0 (0..7) 8 1: 253:16 [8..23]: per-AG metadata 0 (8..23) 16 2: 253:16 [24..39]: inode btree 0 (24..39) 16 3: 253:16 [40..47]: per-AG metadata 0 (40..47) 8 4: 253:16 [48..55]: refcount btree 0 (48..55) 8 5: 253:16 [56..103]: per-AG metadata 0 (56..103) 48 6: 253:16 [104..127]: free space 0 (104..127) 24 ......
Bug: [root@fedora ~]# xfs_io -c 'fsmap -vvvv -d 0 3' /mnt [root@fedora ~]# Normally, we should be able to get one record, but we got nothing.
The root cause of this problem lies in the incorrect setting of rm_owner in the rmap query. In the case of the initial query where the owner is not set, __xfs_getfsmap_datadev() first sets info->high.rm_owner to ULLONG_MAX. This is done to prevent any omissions when comparing rmap items. However, if the current ag is detected to be the last one, the function sets info's high_irec based on the provided key. If high->rm_owner is not specified, it should continue to be set to ULLONG_MAX; otherwise, there will be issues with interval omissions. For example, consider "start" and "end" within the same block. If high->rm_owner == 0, it will be smaller than the founded record in rmapbt, resulting in a query with no records. The main call stack is as follows:
xfs_ioc_getfsmap xfs_getfsmap xfs_getfsmap_datadev_rmapbt __xfs_getfsmap_datadev info->high.rm_owner = ULLONG_MAX if (pag->pag_agno == end_ag) xfs_fsmap_owner_to_rmap // set info->high.rm_owner = 0 because fmr_owner == -1ULL dest->rm_owner = 0 // get nothing xfs_getfsmap_datadev_rmapbt_query
The problem can be resolved by simply modify the xfs_fsmap_owner_to_rmap function internal logic to achieve.
After applying this patch, the above problem have been solved: [root@fedora ~]# xfs_io -c 'fsmap -vvvv -d 0 3' /mnt EXT: DEV BLOCK-RANGE OWNER FILE-OFFSET AG AG-OFFSET TOTAL 0: 253:16 [0..7]: static fs metadata 0 (0..7) 8
Fixes: e89c041338ed ("xfs: implement the GETFSMAP ioctl") Signed-off-by: Zizhi Wo wozizhi@huawei.com Reviewed-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Chandan Babu R chandanbabu@kernel.org Signed-off-by: Leah Rumancik leah.rumancik@gmail.com Acked-by: "Darrick J. Wong" djwong@kernel.org --- fs/xfs/xfs_fsmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c index 956a5670e56c..1efd18437ca4 100644 --- a/fs/xfs/xfs_fsmap.c +++ b/fs/xfs/xfs_fsmap.c @@ -69,11 +69,11 @@ xfs_fsmap_owner_to_rmap( }
switch (src->fmr_owner) { case 0: /* "lowest owner id possible" */ case -1ULL: /* "highest owner id possible" */ - dest->rm_owner = 0; + dest->rm_owner = src->fmr_owner; break; case XFS_FMR_OWN_FREE: dest->rm_owner = XFS_RMAP_OWN_NULL; break; case XFS_FMR_OWN_UNKNOWN: