Currently there are two corner cases not handling compat RO flags
correctly:
- Remount
We can still mount the fs RO with compat RO flags, then remount it RW.
We should not allow any write into a fs with unsupported RO flags.
- Still try to search block group items
In fact, behavior/on-disk format change to extent tree should not
need a full incompat flag.
And since we can ensure fs with unsupported RO flags never got any
writes (with above case fixed), then we can even skip block group
items search at mount time.
This patch will enhance the unsupported RO compat flags by:
- Reject RW remount if there is unsupported RO compat flags
- Go dummy block group items directly for unsupported RO compat flags
In fact, only changes to chunk/subvolume/root/csum trees should go
incompat flags.
The latter part should allow future change to extent tree to be compat
RO flags.
Thus this patch also needs to be backported to all stable trees.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
This patch will be the basis for the revived version of skinny bg tree.
But considering it's fixing an existing problem, and will open the
window for more extent tree change to be RO compat flags, it's sent out
independently.
---
fs/btrfs/block-group.c | 11 ++++++++++-
fs/btrfs/super.c | 9 +++++++++
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index e930749770ac..0148a6d719a4 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -2199,7 +2199,16 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
int need_clear = 0;
u64 cache_gen;
- if (!root)
+ /*
+ * Either no extent root (with ibadroots rescue option) or we have
+ * unsupporter RO options. The fs can never be mounted RW, so no
+ * need to waste time search block group items.
+ *
+ * This also allows new extent tree related changes to be RO compat,
+ * no need for a full incompat flag.
+ */
+ if (!root || (btrfs_super_compat_ro_flags(info->super_copy) &
+ ~BTRFS_FEATURE_COMPAT_RO_SUPP))
return fill_dummy_bgs(info);
key.objectid = 0;
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4c7089b1681b..7d3213e67fb5 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2110,6 +2110,15 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
ret = -EINVAL;
goto restore;
}
+ if (btrfs_super_compat_ro_flags(fs_info->super_copy) &
+ ~BTRFS_FEATURE_COMPAT_RO_SUPP) {
+ btrfs_err(fs_info,
+ "can not remount read-write due to unsupported optional flags 0x%llx",
+ btrfs_super_compat_ro_flags(fs_info->super_copy) &
+ ~BTRFS_FEATURE_COMPAT_RO_SUPP);
+ ret = -EINVAL;
+ goto restore;
+ }
if (fs_info->fs_devices->rw_devices == 0) {
ret = -EACCES;
goto restore;
--
2.36.1
