linux-kernel - [PATCH v7 4/7] fuse: Cache a NULL acl when FUSE

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Date:   Mon, 26 Feb 2018 17:52:59 -0600
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, Alban Crequy <alban@...volk.io>,
        Seth Forshee <seth.forshee@...onical.com>,
        Sargun Dhillon <sargun@...gun.me>,
        Dongsu Park <dongsu@...volk.io>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH v7 4/7] fuse: Cache a NULL acl when FUSE_GETXATTR returns -ENOSYS

When FUSE_GETXATTR will never return anything call cache_no_acl to
cache that state in the vfs as well in fuse with fc->no_getxattr.

The only code path this affects are the code paths that call
fuse_get_acl and caching a NULL or returning it immediately
is exactly the same effect so this should not effect anything.

This keeps the vfs from waisting it's time calling down into fuse
when fuse isn't going to do anything, and it makes it clear
when a NULL should be cached for optimal performance.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/fuse/xattr.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
index 3caac46b08b0..0520a4f47226 100644
--- a/fs/fuse/xattr.c
+++ b/fs/fuse/xattr.c
@@ -82,6 +82,7 @@ ssize_t fuse_getxattr(struct inode *inode, const char *name, void *value,
 		ret = min_t(ssize_t, outarg.size, XATTR_SIZE_MAX);
 	if (ret == -ENOSYS) {
 		fc->no_getxattr = 1;
+		cache_no_acl(inode);
 		ret = -EOPNOTSUPP;
 	}
 	return ret;
-- 
2.14.1