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authorEric Biggers <ebiggers@google.com>2017-05-02 07:49:54 +0300
committerTheodore Ts'o <tytso@mit.edu>2017-05-02 07:49:54 +0300
commitaa1dca3bd96bfd0ddf6871fc1844bd12ccce50f1 (patch)
tree2ea2c003ce1e5b5b82e837c987541a44246b36bd /fs/ext4
parent72d622b42258a0ed0b6e8c0f40d7628de935d058 (diff)
downloadlinux-aa1dca3bd96bfd0ddf6871fc1844bd12ccce50f1.tar.xz
ext4: inherit encryption xattr before other xattrs
When using both encryption and SELinux (or another feature that requires an xattr per file) on a filesystem with 256-byte inodes, each file's xattrs usually spill into an external xattr block. Currently, the xattrs are inherited in the order ACL, security, then encryption. Therefore, if spillage occurs, the encryption xattr will always end up in the external block. This is not ideal because the encryption xattrs contain a nonce, so they will always be unique and will prevent the external xattr blocks from being deduplicated. To improve the situation, change the inheritance order to encryption, ACL, then security. This gives the encryption xattr a better chance to be stored in-inode, allowing the other xattr(s) to be deduplicated. Note that it may be better for userspace to format the filesystem with 512-byte inodes in this case. However, it's not the default. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/ialloc.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 17bc043308f3..98ac2f1f23b3 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1098,6 +1098,17 @@ got:
if (err)
goto fail_drop;
+ /*
+ * Since the encryption xattr will always be unique, create it first so
+ * that it's less likely to end up in an external xattr block and
+ * prevent its deduplication.
+ */
+ if (encrypt) {
+ err = fscrypt_inherit_context(dir, inode, handle, true);
+ if (err)
+ goto fail_free_drop;
+ }
+
err = ext4_init_acl(handle, inode, dir);
if (err)
goto fail_free_drop;
@@ -1119,12 +1130,6 @@ got:
ei->i_datasync_tid = handle->h_transaction->t_tid;
}
- if (encrypt) {
- err = fscrypt_inherit_context(dir, inode, handle, true);
- if (err)
- goto fail_free_drop;
- }
-
err = ext4_mark_inode_dirty(handle, inode);
if (err) {
ext4_std_error(sb, err);