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fs, fscrypt: add an S_ENCRYPTED inode flag

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Introduce a flag S_ENCRYPTED which can be set in ->i_flags to indicate
that the inode is encrypted using the fscrypt (fs/crypto/) mechanism.

Checking this flag will give the same information that
inode->i_sb->s_cop->is_encrypted(inode) currently does, but will be more
efficient.  This will be useful for adding higher-level helper functions
for filesystems to use.  For example we'll be able to replace this:

	if (ext4_encrypted_inode(inode)) {
		ret = fscrypt_get_encryption_info(inode);
		if (ret)
			return ret;
		if (!fscrypt_has_encryption_key(inode))
			return -ENOKEY;
	}

with this:

	ret = fscrypt_require_key(inode);
	if (ret)
		return ret;

... since we'll be able to retain the fast path for unencrypted files as
a single flag check, using an inline function.  This wasn't possible
before because we'd have had to frequently call through the
->i_sb->s_cop->is_encrypted function pointer, even when the encryption
support was disabled or not being used.

Note: we don't define S_ENCRYPTED to 0 if CONFIG_FS_ENCRYPTION is
disabled because we want to continue to return an error if an encrypted
file is accessed without encryption support, rather than pretending that
it is unencrypted.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Acked-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Eric Biggers
2017-10-09 12:15:35 -07:00
committed by Theodore Ts'o
parent 734f0d241d
commit 2ee6a576be
7 changed files with 23 additions and 6 deletions
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7
fs/ext4/inode.c
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@@ -4589,10 +4589,13 @@ void ext4_set_inode_flags(struct inode *inode)
new_fl |= S_DIRSYNC;
if (test_opt(inode->i_sb, DAX) && S_ISREG(inode->i_mode) &&
!ext4_should_journal_data(inode) && !ext4_has_inline_data(inode) &&
!ext4_encrypted_inode(inode))
!(flags & EXT4_ENCRYPT_FL))
new_fl |= S_DAX;
if (flags & EXT4_ENCRYPT_FL)
new_fl |= S_ENCRYPTED;
inode_set_flags(inode, new_fl,
S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX);
S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX|
S_ENCRYPTED);
}
static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,