Re: [PATCH v2 2/2] f2fs: Advertise encrypted casefolding in sysfs

From: Chao Yu
Date: Fri Jun 04 2021 - 20:11:44 EST


On 2021/6/4 13:38, Jaegeuk Kim wrote:
On 06/03, Eric Biggers wrote:
On Thu, Jun 03, 2021 at 09:45:25PM -0700, Jaegeuk Kim wrote:
On 06/03, Eric Biggers wrote:
On Thu, Jun 03, 2021 at 09:50:38AM +0000, Daniel Rosenberg wrote:
Older kernels don't support encryption with casefolding. This adds
the sysfs entry encrypted_casefold to show support for those combined
features. Support for this feature was originally added by
commit 7ad08a58bf67 ("f2fs: Handle casefolding with Encryption")

Fixes: 7ad08a58bf67 ("f2fs: Handle casefolding with Encryption")
Cc: stable@xxxxxxxxxxxxxxx # v5.11+
Signed-off-by: Daniel Rosenberg <drosen@xxxxxxxxxx>
---
fs/f2fs/sysfs.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 09e3f258eb52..6604291a3cdf 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -161,6 +161,9 @@ static ssize_t features_show(struct f2fs_attr *a,
if (f2fs_sb_has_compression(sbi))
len += scnprintf(buf + len, PAGE_SIZE - len, "%s%s",
len ? ", " : "", "compression");
+ if (f2fs_sb_has_casefold(sbi) && f2fs_sb_has_encrypt(sbi))
+ len += scnprintf(buf + len, PAGE_SIZE - len, "%s%s",
+ len ? ", " : "", "encrypted_casefold");
len += scnprintf(buf + len, PAGE_SIZE - len, "%s%s",
len ? ", " : "", "pin_file");
len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
@@ -579,6 +582,7 @@ enum feat_id {
FEAT_CASEFOLD,
FEAT_COMPRESSION,
FEAT_TEST_DUMMY_ENCRYPTION_V2,
+ FEAT_ENCRYPTED_CASEFOLD,
};

Actually looking at it more closely, this patch is wrong.

It only makes sense to declare "encrypted_casefold" as a feature of the
filesystem implementation, i.e. /sys/fs/f2fs/features/encrypted_casefold.

It does *not* make sense to declare it as a feature of a particular filesystem
instance, i.e. /sys/fs/f2fs/$disk/features, as it is already implied by the
filesystem instance having both the encryption and casefold features enabled.

Can we add /sys/fs/f2fs/features/encrypted_casefold only?

wait.. /sys/fs/f2fs/features/encrypted_casefold is on by
CONFIG_FS_ENCRYPTION && CONFIG_UNICODE.
OTOH, /sys/fs/f2fs/$dis/feature_list/encrypted_casefold is on by
on-disk features: F2FS_FEATURE_ENCRYPT and F2FS_FEATURE_CASEFOLD.


Yes, but in the on-disk case, encrypted_casefold is redundant because it simply
means encrypt && casefold. There is no encrypted_casefold flag on-disk.

I prefer to keep encrypted_casefold likewise kernel feature, which is more
intuitive to users.

encrypted_casefold is a kernel feature support flag, not a disk one, IMO, it's
not needed to add it in to per-disk feature list, it may mislead user that
compatible encrypted casefold needs a extra disk layout support while disk has
already encrypted and casefold feature enabled.

Thanks,



- Eric