diff mbox series

[f2fs-dev,v2,4/7] libfs: Support revalidation of encrypted case-insensitive dentries

Message ID 20230422000310.1802-5-krisman@suse.de (mailing list archive)
State Superseded
Headers show
Series Support negative dentries on case-insensitive ext4 and f2fs | expand

Commit Message

Gabriel Krisman Bertazi April 22, 2023, 12:03 a.m. UTC 
From: Gabriel Krisman Bertazi <krisman@collabora.com>

Preserve the existing behavior for encrypted directories, by rejecting
negative dentries of encrypted+casefolded directories.  This allows
generic_ci_d_revalidate to be used by filesystems with both features
enabled, as long as the directory is either casefolded or encrypted, but
not both at the same time.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
 fs/libfs.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Eric Biggers July 14, 2023, 5:31 a.m. UTC | #1 
On Fri, Apr 21, 2023 at 08:03:07PM -0400, Gabriel Krisman Bertazi wrote:
> From: Gabriel Krisman Bertazi <krisman@collabora.com>
> 
> Preserve the existing behavior for encrypted directories, by rejecting
> negative dentries of encrypted+casefolded directories.  This allows
> generic_ci_d_revalidate to be used by filesystems with both features
> enabled, as long as the directory is either casefolded or encrypted, but
> not both at the same time.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> ---
>  fs/libfs.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/libfs.c b/fs/libfs.c
> index f8881e29c5d5..0886044db593 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -1478,6 +1478,9 @@ static inline int generic_ci_d_revalidate(struct dentry *dentry,
>  		const struct inode *dir = READ_ONCE(parent->d_inode);
>  
>  		if (dir && needs_casefold(dir)) {
> +			if (IS_ENCRYPTED(dir))
> +				return 0;
> +

Why not allow negative dentries in case-insensitive encrypted directories?
I can't think any reason why it wouldn't just work.

- Eric
Gabriel Krisman Bertazi July 18, 2023, 7:34 p.m. UTC | #2 
Eric Biggers <ebiggers@kernel.org> writes:

> On Fri, Apr 21, 2023 at 08:03:07PM -0400, Gabriel Krisman Bertazi wrote:
>> From: Gabriel Krisman Bertazi <krisman@collabora.com>
>> 
>> Preserve the existing behavior for encrypted directories, by rejecting
>> negative dentries of encrypted+casefolded directories.  This allows
>> generic_ci_d_revalidate to be used by filesystems with both features
>> enabled, as long as the directory is either casefolded or encrypted, but
>> not both at the same time.
>> 
>> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
>> ---
>>  fs/libfs.c | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>> 
>> diff --git a/fs/libfs.c b/fs/libfs.c
>> index f8881e29c5d5..0886044db593 100644
>> --- a/fs/libfs.c
>> +++ b/fs/libfs.c
>> @@ -1478,6 +1478,9 @@ static inline int generic_ci_d_revalidate(struct dentry *dentry,
>>  		const struct inode *dir = READ_ONCE(parent->d_inode);
>>  
>>  		if (dir && needs_casefold(dir)) {
>> +			if (IS_ENCRYPTED(dir))
>> +				return 0;
>> +
>
> Why not allow negative dentries in case-insensitive encrypted directories?
> I can't think any reason why it wouldn't just work.

TBH, I'm not familiar with the details of combined encrypted+casefold
support to be confident it works.  This patch preserves the current
behavior of disabling them for encrypted+casefold directories.

I suspect it might require extra work that I'm not focusing on this
patchset.  For instance, what should be the order of
fscrypt_d_revalidate and the checks I'm adding here? Note we will start
creating negative dentries in casefold directories after patch 6/7, so
unless we disable it here, we will start calling fscrypt_d_revalidate
for negative+casefold.

Should I just drop this hunk?  Unless you are confident it works as is, I
prefer to add this support in stages and keep negative dentries of
encrypted+casefold directories disabled for now.
Eric Biggers July 18, 2023, 10:10 p.m. UTC | #3 
On Tue, Jul 18, 2023 at 03:34:13PM -0400, Gabriel Krisman Bertazi wrote:
> Eric Biggers <ebiggers@kernel.org> writes:
> 
> > On Fri, Apr 21, 2023 at 08:03:07PM -0400, Gabriel Krisman Bertazi wrote:
> >> From: Gabriel Krisman Bertazi <krisman@collabora.com>
> >> 
> >> Preserve the existing behavior for encrypted directories, by rejecting
> >> negative dentries of encrypted+casefolded directories.  This allows
> >> generic_ci_d_revalidate to be used by filesystems with both features
> >> enabled, as long as the directory is either casefolded or encrypted, but
> >> not both at the same time.
> >> 
> >> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> >> ---
> >>  fs/libfs.c | 8 ++++++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/fs/libfs.c b/fs/libfs.c
> >> index f8881e29c5d5..0886044db593 100644
> >> --- a/fs/libfs.c
> >> +++ b/fs/libfs.c
> >> @@ -1478,6 +1478,9 @@ static inline int generic_ci_d_revalidate(struct dentry *dentry,
> >>  		const struct inode *dir = READ_ONCE(parent->d_inode);
> >>  
> >>  		if (dir && needs_casefold(dir)) {
> >> +			if (IS_ENCRYPTED(dir))
> >> +				return 0;
> >> +
> >
> > Why not allow negative dentries in case-insensitive encrypted directories?
> > I can't think any reason why it wouldn't just work.
> 
> TBH, I'm not familiar with the details of combined encrypted+casefold
> support to be confident it works.This patch preserves the current
> behavior of disabling them for encrypted+casefold directories.

Not allowing that combination reduces the usefulness of this patchset.
Note that Android's use of casefold is always combined with encryption.

> I suspect it might require extra work that I'm not focusing on this
> patchset.  For instance, what should be the order of
> fscrypt_d_revalidate and the checks I'm adding here?

Why would order matter?  If either "feature" wants the dentry to be invalidated,
then the dentry gets invalidated.

> Note we will start creating negative dentries in casefold directories after
> patch 6/7, so unless we disable it here, we will start calling
> fscrypt_d_revalidate for negative+casefold.

fscrypt_d_revalidate() only cares about the DCACHE_NOKEY_NAME flag, so that's
not a problem.

> 
> Should I just drop this hunk?  Unless you are confident it works as is, I
> prefer to add this support in stages and keep negative dentries of
> encrypted+casefold directories disabled for now.

Unless I'm missing something, I think you're overcomplicating it.  It should
just work if you don't go out of your way to prohibit this case.  I.e., just
don't add the IS_ENCRYPTED(dir) check to generic_ci_d_revalidate().

- Eric
Gabriel Krisman Bertazi July 19, 2023, 6:27 p.m. UTC | #4 
Eric Biggers <ebiggers@kernel.org> writes:

> Why would order matter?  If either "feature" wants the dentry to be invalidated,
> then the dentry gets invalidated.

For instance, I was wondering makes sense for instance to memcmp d_name for
!DCACHE_NOKEY_NAME or if we wanted fscrypt_d_revalidate to come first.

>> Note we will start creating negative dentries in casefold directories after
>> patch 6/7, so unless we disable it here, we will start calling
>> fscrypt_d_revalidate for negative+casefold.
>
> fscrypt_d_revalidate() only cares about the DCACHE_NOKEY_NAME flag, so that's
> not a problem.

..I see now it is the first thing checked in fscrypt_d_revalidate.

>> Should I just drop this hunk?  Unless you are confident it works as is, I
>> prefer to add this support in stages and keep negative dentries of
>> encrypted+casefold directories disabled for now.
>
> Unless I'm missing something, I think you're overcomplicating it.

Not overcomplicating. I'm just not familiar with fscrypt details enough to be
sure I could enable it.  But yes, it seems safe.

> It should
> just work if you don't go out of your way to prohibit this case.  I.e., just
> don't add the IS_ENCRYPTED(dir) check to generic_ci_d_revalidate().

I'll drop the check. And resend.

Thanks,
diff mbox series

Patch

diff --git a/fs/libfs.c b/fs/libfs.c
index f8881e29c5d5..0886044db593 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1478,6 +1478,9 @@  static inline int generic_ci_d_revalidate(struct dentry *dentry,
 		const struct inode *dir = READ_ONCE(parent->d_inode);
 
 		if (dir && needs_casefold(dir)) {
+			if (IS_ENCRYPTED(dir))
+				return 0;
+
 			if (!d_is_casefold_lookup(dentry))
 				return 0;
 
@@ -1497,7 +1500,8 @@  static inline int generic_ci_d_revalidate(struct dentry *dentry,
 			}
 		}
 	}
-	return 1;
+
+	return fscrypt_d_revalidate(dentry, flags);
 }
 
 static const struct dentry_operations generic_ci_dentry_ops = {
@@ -1517,7 +1521,7 @@  static const struct dentry_operations generic_encrypted_dentry_ops = {
 static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
 	.d_hash = generic_ci_d_hash,
 	.d_compare = generic_ci_d_compare,
-	.d_revalidate = fscrypt_d_revalidate,
+	.d_revalidate_name = generic_ci_d_revalidate,
 };
 #endif