fs: block_dump missing dentry locking

I think the block_dump output in __mark_inode_dirty is missing dentry locking.
Surely the i_dentry list can change any time, so we may not even *get* a
dentry there. If we do get one by chance, then it would appear to be able to
go away or get renamed at any time...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 24 insertions, 17 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index efcedb6d9cbc..40308e98c6a4 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -64,6 +64,28 @@ static void writeback_release(struct backing_dev_info *bdi)
         clear_bit(BDI_pdflush, &bdi->state);
 }
 
+static noinline void block_dump___mark_inode_dirty(struct inode *inode)
+{
+        if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
+                struct dentry *dentry;
+                const char *name = "?";
+
+                dentry = d_find_alias(inode);
+                if (dentry) {
+                        spin_lock(&dentry->d_lock);
+                        name = (const char *) dentry->d_name.name;
+                }
+                printk(KERN_DEBUG
+                       "%s(%d): dirtied inode %lu (%s) on %s\n",
+                       current->comm, task_pid_nr(current), inode->i_ino,
+                       name, inode->i_sb->s_id);
+                if (dentry) {
+                        spin_unlock(&dentry->d_lock);
+                        dput(dentry);
+                }
+        }
+}
+
 /**
  *      __mark_inode_dirty -    internal function
  *      @inode: inode to mark
@@ -114,23 +136,8 @@ void __mark_inode_dirty(struct inode *inode, int flags)
         if ((inode->i_state & flags) == flags)
                 return;
 
-        if (unlikely(block_dump)) {
-                struct dentry *dentry = NULL;
-                const char *name = "?";
-
-                if (!list_empty(&inode->i_dentry)) {
-                        dentry = list_entry(inode->i_dentry.next,
-                                            struct dentry, d_alias);
-                        if (dentry && dentry->d_name.name)
-                                name = (const char *) dentry->d_name.name;
-                }
-
-                if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev"))
-                        printk(KERN_DEBUG
-                               "%s(%d): dirtied inode %lu (%s) on %s\n",
-                               current->comm, task_pid_nr(current), inode->i_ino,
-                               name, inode->i_sb->s_id);
-        }
+        if (unlikely(block_dump))
+                block_dump___mark_inode_dirty(inode);
 
         spin_lock(&inode_lock);
         if ((inode->i_state & flags) != flags) {