From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Thu, 7 May 2009 23:05:06 +0000 (+0200)
Subject: kill-the-bkl/reiserfs: don't hold the write recursively in reiserfs_lookup()
X-Git-Tag: firefly_0821_release~9833^2~3455^2~37
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=b1c839bb2d8d6f1f6bf48f5c657752b4963f88f8;p=firefly-linux-kernel-4.4.55.git

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>
---

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);
 	}