From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
This check was added by Al Viro with
d9e80b7de91db05c1c4d2e5ebbfd70b3b3ba0e0f "nfs d_revalidate() is too
trigger-happy with d_drop()", with the explanation that we don't want to
remove the root of a disconnected tree, which will still be included on
the s_anon list.
But DCACHE_DISCONNECTED does *not* actually identify dentries that are
disconnected from the dentry tree or hashed on s_anon. IS_ROOT() is the
way to do that.
Also add a comment from Al's commit to remind us why this check is
there.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
---
fs/nfs/dir.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index de434f3..2acc77a 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1139,7 +1139,13 @@ out_zap_parent:
if (inode && S_ISDIR(inode->i_mode)) {
/* Purge readdir caches. */
nfs_zap_caches(inode);
- if (dentry->d_flags & DCACHE_DISCONNECTED)
+ /*
+ * We can't d_drop the root of a disconnected tree:
+ * its d_hash is on the s_anon list and d_drop() would hide
+ * it from shrink_dcache_for_unmount(), leading to busy
+ * inodes on unmount and further oopses.
+ */
+ if (IS_ROOT(dentry))
goto out_valid;
}
/* If we have submounts, don't unhash ! */
--
1.7.9.5
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