Under low-memory conditions, close_all_cached_dirs() can't move the
dentries to a separate list to dput() them once the locks are dropped.
This will result in a "Dentry still in use" error, so add an error
message that makes it clear this is what happened:
[ 495.281119] CIFS: VFS: \\otters.example.com\share Out of memory while dropping dentries
[ 495.281595] ------------[ cut here ]------------
[ 495.281887] BUG: Dentry ffff888115531138{i=78,n=/} still in use (2) [unmount of cifs cifs]
[ 495.282391] WARNING: CPU: 1 PID: 2329 at fs/dcache.c:1536 umount_check+0xc8/0xf0
Also, bail out of looping through all tcons as soon as a single
allocation fails, since we're already in trouble, and kmalloc() attempts
for subseqeuent tcons are likely to fail just like the first one did.
Signed-off-by: Paul Aurich <paul@xxxxxxxxxxxxxx>
Suggested-by: Ruben Devos <rdevos@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
This could also be folded directly into "smb: During unmount, ensure all
cached dir instances drop their dentry".
---
fs/smb/client/cached_dir.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index 004349a7ab69..8b510c858f4f 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -488,12 +488,21 @@ void close_all_cached_dirs(struct cifs_sb_info *cifs_sb)
if (cfids == NULL)
continue;
spin_lock(&cfids->cfid_list_lock);
list_for_each_entry(cfid, &cfids->entries, entry) {
tmp_list = kmalloc(sizeof(*tmp_list), GFP_ATOMIC);
- if (tmp_list == NULL)
- break;
+ if (tmp_list == NULL) {
+ /*
+ * If the malloc() fails, we won't drop all
+ * dentries, and unmounting is likely to trigger
+ * a 'Dentry still in use' error.
+ */
+ cifs_tcon_dbg(VFS, "Out of memory while dropping dentries\n");
+ spin_unlock(&cfids->cfid_list_lock);
+ spin_unlock(&cifs_sb->tlink_tree_lock);
+ goto done;
+ }
spin_lock(&cfid->fid_lock);
tmp_list->dentry = cfid->dentry;
cfid->dentry = NULL;
spin_unlock(&cfid->fid_lock);
@@ -501,10 +510,11 @@ void close_all_cached_dirs(struct cifs_sb_info *cifs_sb)
}
spin_unlock(&cfids->cfid_list_lock);
}
spin_unlock(&cifs_sb->tlink_tree_lock);
+done:
list_for_each_entry_safe(tmp_list, q, &entry, entry) {
list_del(&tmp_list->entry);
dput(tmp_list->dentry);
kfree(tmp_list);
}
--
2.45.2
