[RFC PATCH 1/3] ext4: show prjquota info on statfs for a file

[Chengguang Xu]

Currently we replace filesystem statistics using prjquota info
on statfs when specified directory has project id inherit flag.
However, statfs on a file(accurately non-dir) which is under the
project quota dir(with inherit flag) still shows whole filesystem
statistics. In container use case, it will give container user
inconsistent experience and cause confusion about available free
space.

Detail info like below:
We use project quota to limit disk space usage for a container
and run df command inside container.

Run df on a directory:

[root /]# df -h /etc/
Filesystem Size Used Avail Use% Mounted on
kataSharedÂÂÂÂÂ 1.0GÂÂ 13M 1012MÂÂ 2% /

Run df on a file:

[root /]# df -h /etc/exports
Filesystem Size Used Avail Use% Mounted on
kataSharedÂÂÂÂÂ 1.5TÂ 778MÂ 1.5TÂÂ 1% /

Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
---
 fs/ext4/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index dd654e53ba3d..3fba22b54f5c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5607,7 +5607,8 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_fsid.val[1] = (fsid >> 32) & 0xFFFFFFFFUL;
 
 #ifdef CONFIG_QUOTA
-	if (ext4_test_inode_flag(dentry->d_inode, EXT4_INODE_PROJINHERIT) &&
+	if ((ext4_test_inode_flag(dentry->d_inode, EXT4_INODE_PROJINHERIT) ||
+	     !S_ISDIR(dentry->d_inode->i_mode)) &&
 	    sb_has_quota_limits_enabled(sb, PRJQUOTA))
 		ext4_statfs_project(sb, EXT4_I(dentry->d_inode)->i_projid, buf);
 #endif
-- 
2.20.1