fscrypt: document that CephFS supports fscrypt now

The help text for CONFIG_FS_ENCRYPTION and the fscrypt.rst documentation
file both list the filesystems that support fscrypt.  CephFS added
support for fscrypt in v6.6, so add CephFS to the list.

Link: https://lore.kernel.org/r/20231227045158.87276-1-ebiggers@kernel.orgSigned-off-by: Eric Biggers <ebiggers@google.com>

Documentation/filesystems/fscrypt.rst

@@ -31,15 +31,15 @@ However, except for filenames, fscrypt does not encrypt filesystem
 metadata.
 
 Unlike eCryptfs, which is a stacked filesystem, fscrypt is integrated
-directly into supported filesystems --- currently ext4, F2FS, and
-UBIFS.  This allows encrypted files to be read and written without
-caching both the decrypted and encrypted pages in the pagecache,
-thereby nearly halving the memory used and bringing it in line with
-unencrypted files.  Similarly, half as many dentries and inodes are
-needed.  eCryptfs also limits encrypted filenames to 143 bytes,
-causing application compatibility issues; fscrypt allows the full 255
-bytes (NAME_MAX).  Finally, unlike eCryptfs, the fscrypt API can be
-used by unprivileged users, with no need to mount anything.
+directly into supported filesystems --- currently ext4, F2FS, UBIFS,
+and CephFS.  This allows encrypted files to be read and written
+without caching both the decrypted and encrypted pages in the
+pagecache, thereby nearly halving the memory used and bringing it in
+line with unencrypted files.  Similarly, half as many dentries and
+inodes are needed.  eCryptfs also limits encrypted filenames to 143
+bytes, causing application compatibility issues; fscrypt allows the
+full 255 bytes (NAME_MAX).  Finally, unlike eCryptfs, the fscrypt API
+can be used by unprivileged users, with no need to mount anything.
 
 fscrypt does not support encrypting files in-place.  Instead, it
 supports marking an empty directory as encrypted.  Then, after

fs/crypto/Kconfig

@@ -11,7 +11,7 @@ config FS_ENCRYPTION
 	  feature is similar to ecryptfs, but it is more memory
 	  efficient since it avoids caching the encrypted and
 	  decrypted pages in the page cache.  Currently Ext4,
-	  F2FS and UBIFS make use of this feature.
+	  F2FS, UBIFS, and CephFS make use of this feature.
 
 # Filesystems supporting encryption must select this if FS_ENCRYPTION.  This
 # allows the algorithms to be built as modules when all the filesystems are,