ext4 and ceph already have a folio to pass; f2fs needs to be properly
converted but this will do for now.  This removes a reference
to page->index and page->mapping as well as removing a call to
compound_head().

Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Link: https://lore.kernel.org/r/20250304170224.523141-1-willy@infradead.org
Acked-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

->d_revalidate() often needs to access dentry parent and name; that has
to be done carefully, since the locking environment varies from caller
to caller.  We are not guaranteed that dentry in question will not be
moved right under us - not unless the filesystem is such that nothing
on it ever gets renamed.

It can be dealt with, but that results in boilerplate code that isn't
even needed - the callers normally have just found the dentry via dcache
lookup and want to verify that it's in the right place; they already
have the values of ->d_parent and ->d_name stable.  There is a couple
of exceptions (overlayfs and, to less extent, ecryptfs), but for the
majority of calls that song and dance is not needed at all.

It's easier to make ecryptfs and overlayfs find and pass those values if
there's a ->d_revalidate() instance to be called, rather than doing that
in the instances.

This commit only changes the calling conventions; making use of supplied
values is left to followups.

NOTE: some instances need more than just the parent - things like CIFS
may need to build an entire path from filesystem root, so they need
more precautions than the usual boilerplate.  This series doesn't
do anything to that need - these filesystems have to keep their locking
mechanisms (rename_lock loops, use of dentry_path_raw(), private rwsem
a-la v9fs).

One thing to keep in mind when using name is that name->name will normally
point into the pathname being resolved; the filename in question occupies
name->len bytes starting at name->name, and there is NUL somewhere after it,
but it the next byte might very well be '/' rather than '\0'.  Do not
ignore name->len.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Gabriel Krisman Bertazi <gabriel@krisman.be>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

When a key is added, existing directory dentries in the
DCACHE_NOKEY_NAME form are moved by the VFS to the plaintext version.
But, since they have the DCACHE_OP_REVALIDATE flag set, revalidation
will be done at each lookup only to return immediately, since plaintext
dentries can't go stale until eviction.  This patch optimizes this case,
by dropping the flag once the nokey_name dentry becomes plain-text.
Note that non-directory dentries are not moved this way, so they won't
be affected.

Of course, this can only be done if fscrypt is the only thing requiring
revalidation for a dentry.  For this reason, we only disable
d_revalidate if the .d_revalidate hook is fscrypt_d_revalidate itself.

It is safe to do it here because when moving the dentry to the
plain-text version, we are holding the d_lock.  We might race with a
concurrent RCU lookup but this is harmless because, at worst, we will
get an extra d_revalidate on the keyed dentry, which will still find the
dentry to be valid.

Finally, now that we do more than just clear the DCACHE_NOKEY_NAME in
fscrypt_handle_d_move, skip it entirely for plaintext dentries, to avoid
extra costs.

Reviewed-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240221171412.10710-5-krisman@suse.de
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>

Unencrypted and encrypted-dentries where the key is available don't need
to be revalidated by fscrypt, since they don't go stale from under VFS
and the key cannot be removed for the encrypted case without evicting
the dentry.  Disable their d_revalidate hook on the first lookup, to
avoid repeated revalidation later. This is done in preparation to always
configuring d_op through sb->s_d_op.

The only part detail is that, since the filesystem might have other
features that require revalidation, we only apply this optimization if
the d_revalidate handler is fscrypt_d_revalidate itself.

Finally, we need to clean the dentry->flags even for unencrypted
dentries, so the ->d_lock might be acquired even for them.  In order to
avoid doing it for filesystems that don't care about fscrypt at all, we
peek ->d_flags without the lock at first, and only acquire it if we
actually need to write the flag.

Reviewed-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240221171412.10710-4-krisman@suse.de
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>

Both fscrypt_prepare_lookup_partial and fscrypt_prepare_lookup will set
DCACHE_NOKEY_NAME for dentries when the key is not available. Extract
out a helper to set this flag in a single place, in preparation to also
add the optimization that will disable ->d_revalidate if possible.

Reviewed-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240221171412.10710-3-krisman@suse.de
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>

We are going to track per-extent information, so it'll be necessary to
distinguish between inode infos and extent infos.  Rename fscrypt_info
to fscrypt_inode_info, adjusting any lines that now exceed 80
characters.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ebiggers: rebased onto fscrypt tree, renamed fscrypt_get_info(),
 adjusted two comments, and fixed some lines over 80 characters]
Link: https://lore.kernel.org/r/20231005025757.33521-1-ebiggers@kernel.org
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Until now, fscrypt has always used the filesystem block size as the
granularity of file contents encryption.  Two scenarios have come up
where a sub-block granularity of contents encryption would be useful:

1. Inline crypto hardware that only supports a crypto data unit size
   that is less than the filesystem block size.

2. Support for direct I/O at a granularity less than the filesystem
   block size, for example at the block device's logical block size in
   order to match the traditional direct I/O alignment requirement.

(1) first came up with older eMMC inline crypto hardware that only
supports a crypto data unit size of 512 bytes.  That specific case
ultimately went away because all systems with that hardware continued
using out of tree code and never actually upgraded to the upstream
inline crypto framework.  But, now it's coming back in a new way: some
current UFS controllers only support a data unit size of 4096 bytes, and
there is a proposal to increase the filesystem block size to 16K.

(2) was discussed as a "nice to have" feature, though not essential,
when support for direct I/O on encrypted files was being upstreamed.

Still, the fact that this feature has come up several times does suggest
it would be wise to have available.  Therefore, this patch implements it
by using one of the reserved bytes in fscrypt_policy_v2 to allow users
to select a sub-block data unit size.  Supported data unit sizes are
powers of 2 between 512 and the filesystem block size, inclusively.
Support is implemented for both the FS-layer and inline crypto cases.

This patch focuses on the basic support for sub-block data units.  Some
things are out of scope for this patch but may be addressed later:

- Supporting sub-block data units in combination with
  FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64, in most cases.  Unfortunately this
  combination usually causes data unit indices to exceed 32 bits, and
  thus fscrypt_supported_policy() correctly disallows it.  The users who
  potentially need this combination are using f2fs.  To support it, f2fs
  would need to provide an option to slightly reduce its max file size.

- Supporting sub-block data units in combination with
  FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32.  This has the same problem
  described above, but also it will need special code to make DUN
  wraparound still happen on a FS block boundary.

- Supporting use case (2) mentioned above.  The encrypted direct I/O
  code will need to stop requiring and assuming FS block alignment.
  This won't be hard, but it belongs in a separate patch.

- Supporting this feature on filesystems other than ext4 and f2fs.
  (Filesystems declare support for it via their fscrypt_operations.)
  On UBIFS, sub-block data units don't make sense because UBIFS encrypts
  variable-length blocks as a result of compression.  CephFS could
  support it, but a bit more work would be needed to make the
  fscrypt_*_block_inplace functions play nicely with sub-block data
  units.  I don't think there's a use case for this on CephFS anyway.

Link: https://lore.kernel.org/r/20230925055451.59499-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

Now that fs/crypto/ computes the filesystem's lblk_bits from its maximum
file size, it is no longer necessary for filesystems to provide
lblk_bits via fscrypt_operations::get_ino_and_lblk_bits.

It is still necessary for fs/crypto/ to retrieve ino_bits from the
filesystem.  However, this is used only to decide whether inode numbers
fit in 32 bits.  Also, ino_bits is static for all relevant filesystems,
i.e. it doesn't depend on the filesystem instance.

Therefore, in the interest of keeping things as simple as possible,
replace 'get_ino_and_lblk_bits' with a flag 'has_32bit_inodes'.  This
can always be changed back to a function if a filesystem needs it to be
dynamic, but for now a static flag is all that's needed.

Link: https://lore.kernel.org/r/20230925055451.59499-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

Replace FS_CFLG_OWN_PAGES with a bit flag 'needs_bounce_pages' which has
the opposite meaning.  I.e., filesystems now opt into the bounce page
pool instead of opt out.  Make fscrypt_alloc_bounce_page() check that
the bounce page pool has been initialized.

I believe the opt-in makes more sense, since nothing else in
fscrypt_operations is opt-out, and these days filesystems can choose to
use blk-crypto which doesn't need the fscrypt bounce page pool.  Also, I
happen to be planning to add two more flags, and I wanted to fix the
"FS_CFLG_" name anyway as it wasn't prefixed with "FSCRYPT_".

Link: https://lore.kernel.org/r/20230925055451.59499-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

fscrypt_operations::key_prefix should not be set by any filesystems that
aren't setting it already.  This is already documented, but apparently
it's not sufficiently clear, as both ceph and btrfs have tried to set
it.  Rename the field to legacy_key_prefix and improve the documentation
to hopefully make it clearer.

Link: https://lore.kernel.org/r/20230925055451.59499-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>