ext4: Add statx support

Return enhanced file attributes from the Ext4 filesystem. This includes
the following:

(1) The inode creation time (i_crtime) as stx_btime, setting STATX_BTIME.

(2) Certain FS_xxx_FL flags are mapped to stx_attribute flags.

This requires that all ext4 inodes have a getattr call, not just some of
them, so to this end, split the ext4_getattr() function and only call part
of it where appropriate.

Example output:

[root@andromeda ~]# touch foo
[root@andromeda ~]# chattr +ai foo
[root@andromeda ~]# /tmp/test-statx foo
statx(foo) = 0
results=fff
Size: 0 Blocks: 0 IO Block: 4096 regular file
Device: 08:12 Inode: 2101950 Links: 1
Access: (0644/-rw-r--r--) Uid: 0 Gid: 0
Access: 2016-02-11 17:08:29.031795451+0000
Modify: 2016-02-11 17:08:29.031795451+0000
Change: 2016-02-11 17:11:11.987790114+0000
Birth: 2016-02-11 17:08:29.031795451+0000
Attributes: 0000000000000030 (-------- -------- -------- -------- -------- -------- -------- --ai----)

Signed-off-by: David Howells <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

fs/ext4/ext4.h

···
 extern int  ext4_getattr(const struct path *, struct kstat *, u32, unsigned int);
 extern void ext4_evict_inode(struct inode *);
 extern void ext4_clear_inode(struct inode *);
+extern int  ext4_file_getattr(const struct path *, struct kstat *, u32, unsigned int);
 extern int  ext4_sync_inode(handle_t *, struct inode *);
 extern void ext4_dirty_inode(struct inode *, int);
 extern int ext4_change_inode_journal_flag(struct inode *, int);

fs/ext4/file.c

···
 
 const struct inode_operations ext4_file_inode_operations = {
 	.setattr	= ext4_setattr,
-	.getattr	= ext4_getattr,
+	.getattr	= ext4_file_getattr,
 	.listxattr	= ext4_listxattr,
 	.get_acl	= ext4_get_acl,
 	.set_acl	= ext4_set_acl,

fs/ext4/inode.c

···
 int ext4_getattr(const struct path *path, struct kstat *stat,
 		 u32 request_mask, unsigned int query_flags)
 {
-	struct inode *inode;
-	unsigned long long delalloc_blocks;
+	struct inode *inode = d_inode(path->dentry);
+	struct ext4_inode *raw_inode;
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	unsigned int flags;
 
-	inode = d_inode(path->dentry);
+	if (EXT4_FITS_IN_INODE(raw_inode, ei, i_crtime)) {
+		stat->result_mask |= STATX_BTIME;
+		stat->btime.tv_sec = ei->i_crtime.tv_sec;
+		stat->btime.tv_nsec = ei->i_crtime.tv_nsec;
+	}
+
+	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
+	if (flags & EXT4_APPEND_FL)
+		stat->attributes |= STATX_ATTR_APPEND;
+	if (flags & EXT4_COMPR_FL)
+		stat->attributes |= STATX_ATTR_COMPRESSED;
+	if (flags & EXT4_ENCRYPT_FL)
+		stat->attributes |= STATX_ATTR_ENCRYPTED;
+	if (flags & EXT4_IMMUTABLE_FL)
+		stat->attributes |= STATX_ATTR_IMMUTABLE;
+	if (flags & EXT4_NODUMP_FL)
+		stat->attributes |= STATX_ATTR_NODUMP;
+
 	generic_fillattr(inode, stat);
+	return 0;
+}
+
+int ext4_file_getattr(const struct path *path, struct kstat *stat,
+		      u32 request_mask, unsigned int query_flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	u64 delalloc_blocks;
+
+	ext4_getattr(path, stat, request_mask, query_flags);
 
 	/*
 	 * If there is inline data in the inode, the inode will normally not

fs/ext4/namei.c

···
 	.tmpfile	= ext4_tmpfile,
 	.rename		= ext4_rename2,
 	.setattr	= ext4_setattr,
+	.getattr	= ext4_getattr,
 	.listxattr	= ext4_listxattr,
 	.get_acl	= ext4_get_acl,
 	.set_acl	= ext4_set_acl,
···
 
 const struct inode_operations ext4_special_inode_operations = {
 	.setattr	= ext4_setattr,
+	.getattr	= ext4_getattr,
 	.listxattr	= ext4_listxattr,
 	.get_acl	= ext4_get_acl,
 	.set_acl	= ext4_set_acl,

fs/ext4/symlink.c

···
 const struct inode_operations ext4_encrypted_symlink_inode_operations = {
 	.get_link	= ext4_encrypted_get_link,
 	.setattr	= ext4_setattr,
+	.getattr	= ext4_getattr,
 	.listxattr	= ext4_listxattr,
 };
 
 const struct inode_operations ext4_symlink_inode_operations = {
 	.get_link	= page_get_link,
 	.setattr	= ext4_setattr,
+	.getattr	= ext4_getattr,
 	.listxattr	= ext4_listxattr,
 };
 
 const struct inode_operations ext4_fast_symlink_inode_operations = {
 	.get_link	= simple_get_link,
 	.setattr	= ext4_setattr,
+	.getattr	= ext4_getattr,
 	.listxattr	= ext4_listxattr,
 };