kill-the-bkl/reiserfs: don't hold the write recursively in reiserfs_lookup()

The write lock can be acquired recursively in reiserfs_lookup(). But we may
want to *really* release the lock before possible rescheduling from a
reiserfs_lookup() callee.

Hence we want to only acquire the lock once (ie: not recursively).

[ Impact: prevent from possible false unreleased write lock on sleeping ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/reiserfs/namei.c b/fs/reiserfs/namei.c
index 271579128634..b3973c9f0bf1 100644
--- a/fs/reiserfs/namei.c
+++ b/fs/reiserfs/namei.c
@@ -324,6 +324,7 @@ static struct dentry *reiserfs_lookup(struct inode *dir, struct dentry *dentry,
                                       struct nameidata *nd)
 {
         int retval;
+        int lock_depth;
         struct inode *inode = NULL;
         struct reiserfs_dir_entry de;
         INITIALIZE_PATH(path_to_entry);
@@ -331,7 +332,13 @@ static struct dentry *reiserfs_lookup(struct inode *dir, struct dentry *dentry,
         if (REISERFS_MAX_NAME(dir->i_sb->s_blocksize) < dentry->d_name.len)
                 return ERR_PTR(-ENAMETOOLONG);
 
-        reiserfs_write_lock(dir->i_sb);
+        /*
+         * Might be called with or without the write lock, must be careful
+         * to not recursively hold it in case we want to release the lock
+         * before rescheduling.
+         */
+        lock_depth = reiserfs_write_lock_once(dir->i_sb);
+
         de.de_gen_number_bit_string = NULL;
         retval =
             reiserfs_find_entry(dir, dentry->d_name.name, dentry->d_name.len,
@@ -341,7 +348,7 @@ static struct dentry *reiserfs_lookup(struct inode *dir, struct dentry *dentry,
                 inode = reiserfs_iget(dir->i_sb,
                                       (struct cpu_key *)&(de.de_dir_id));
                 if (!inode || IS_ERR(inode)) {
-                        reiserfs_write_unlock(dir->i_sb);
+                        reiserfs_write_unlock_once(dir->i_sb, lock_depth);
                         return ERR_PTR(-EACCES);
                 }
 
@@ -350,7 +357,7 @@ static struct dentry *reiserfs_lookup(struct inode *dir, struct dentry *dentry,
                 if (IS_PRIVATE(dir))
                         inode->i_flags |= S_PRIVATE;
         }
-        reiserfs_write_unlock(dir->i_sb);
+        reiserfs_write_unlock_once(dir->i_sb, lock_depth);
         if (retval == IO_ERROR) {
                 return ERR_PTR(-EIO);
         }