On 04/21/2018 10:43 AM, Qu Wenruo wrote:
On 2018年04月21日 10:38, Anand Jain wrote:
On 04/20/2018 11:15 PM, David Sterba wrote:
On Fri, Apr 20, 2018 at 10:32:03PM +0800, Anand Jain wrote:
On 04/19/2018 05:38 PM, Qu Wenruo wrote:
Although we have already checked incompat flags manually before really
mounting it, we could still enhance btrfs_check_super_valid() to check
incompat flags for later write time super block validation check.
This patch adds such incompat flags check for
btrfs_check_super_valid(),
currently it won't be triggered, but provides the basis for later write
time check.
Signed-off-by: Qu Wenruo <[email protected]>
---
fs/btrfs/disk-io.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 60caa68c3618..ec123158f051 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4104,6 +4104,19 @@ static int btrfs_check_super_valid(struct
btrfs_fs_info *fs_info)
ret = -EINVAL;
}
+ /*
+ * Before calling btrfs_check_super_valid() we have already
checked
+ * incompat flags. So if we developr new incompat flags, it's
must be
+ * some corruption.
+ */
+ if (btrfs_super_incompat_flags(sb) &
~BTRFS_FEATURE_INCOMPAT_SUPP) {
+ btrfs_err(fs_info,
+ "corrupted incompat flags detected 0x%llx, supported 0x%llx",
2707 features = btrfs_super_incompat_flags(disk_super) &
2708 ~BTRFS_FEATURE_INCOMPAT_SUPP;
2709 if (features) {
2710 btrfs_err(fs_info,
2711 "cannot mount because of unsupported
optional features (%llx)",
2712 features);
2713 err = -EINVAL;
2714 goto fail_alloc;
2715 }
So there's a "user experience" change, now that you pointed out the
other check.
Its a regression.
If a filesystem with incompat bits set will be mounted,
this will say 'you have corrupted filesystem', which is not IMO what we
want to tell.
Tough the extended btrfs_check_super_valid could catch the corrupted
incompat bits, what we need at mount time is wording from the 2nd
message ("cannot mount unsuppported features").
I think that there should be a separate function that does the
pre-commit checks, calls btrfs_check_super_valid and also validates the
incompat bit.
We can still print it as 'unsupported optional features', which would
imply corruption in the non-mount context.
In that case such wording is not obvious enough to info it's super block
corruption.
If the device is already mounted. Then its a corruption.
Thanks, Anand
So I still prefer current way of checking incompact flags and csum types
manually at mount time before btrfs_validate_super().
David's idea of a separate function to do mount time check and gives
better prompt is pretty good.
Especially for incompat features, as incompat features will increase in
the future and for older kernel info such feature as corruption is not
acceptable.
But currently, there are only 2 members we need to check at mount time
(csum_type and incompat features), and only one caller, current code
looks good enough for its purpose.
Thanks,
Qu
Thanks, Anand
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