linux-kernel - [PATCH] ceph: fix st_nlink stat for directories

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Date:   Mon, 21 May 2018 10:27:29 +0100
From:   Luis Henriques <lhenriques@...e.com>
To:     "Yan, Zheng" <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>
Cc:     ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Luis Henriques <lhenriques@...e.com>
Subject: [PATCH] ceph: fix st_nlink stat for directories

Currently, calling stat on a cephfs directory returns 1 for st_nlink.
This behaviour has recently changed in the fuse client, as some
applications seem to expect this value to be either 0 (if it's
unlinked) or 2 + number of subdirectories.  This behaviour was changed
in the fuse client with commit 67c7e4619188 ("client: use common
interp of st_nlink for dirs").

This patch modifies the kernel client to have a similar behaviour.

Link: https://tracker.ceph.com/issues/23873
Signed-off-by: Luis Henriques <lhenriques@...e.com>
---
 fs/ceph/inode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index aa7c5a4ff137..6ad66ef8fd66 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -2288,6 +2288,14 @@ int ceph_getattr(const struct path *path, struct kstat *stat,
 				stat->size = ci->i_files + ci->i_subdirs;
 			stat->blocks = 0;
 			stat->blksize = 65536;
+			/*
+			 * Some applications rely on the number of st_nlink
+			 * value on directories to be either 0 (if unlinked)
+			 * or 2 + number of subdirectories.
+			 */
+			if (stat->nlink == 1)
+				/* '.' + '..' + subdirs */
+				stat->nlink = 1 + 1 + ci->i_subdirs;
 		}
 	}
 	return err;