fs: rcu-walk aware d_revalidate method

Require filesystems be aware of .d_revalidate being called in rcu-walk
mode (nd->flags & LOOKUP_RCU). For now do a simple push down, returning
-ECHILD from all implementations.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index bfe3f2eb684d..651e4ef563b1 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -315,12 +315,19 @@ out_error:
  */
 static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct inode *dir = dentry->d_parent->d_inode;
-        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
-        int oz_mode = autofs4_oz_mode(sbi);
+        struct inode *dir;
+        struct autofs_sb_info *sbi;
+        int oz_mode;
         int flags = nd ? nd->flags : 0;
         int status = 1;
 
+        if (flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        dir = dentry->d_parent->d_inode;
+        sbi = autofs4_sbi(dir->i_sb);
+        oz_mode = autofs4_oz_mode(sbi);
+
         /* Pending dentry */
         spin_lock(&sbi->fs_lock);
         if (autofs4_ispending(dentry)) {