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Subject[PATCH 4/7] kill-the-bkl/reiserfs: don't hold the write recursively in reiserfs_lookup()
Date
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>
---
fs/reiserfs/namei.c | 15 +++++++++++----
1 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/reiserfs/namei.c b/fs/reiserfs/namei.c
index efd4d72..bed3827 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,
@@ -347,14 +354,14 @@ static struct dentry *reiserfs_lookup(struct inode *dir, struct dentry *dentry,
le32_to_cpu(INODE_PKEY
(REISERFS_SB(dir->i_sb)->priv_root->d_inode)->
k_objectid)) {
- reiserfs_write_unlock(dir->i_sb);
+ reiserfs_write_unlock_once(dir->i_sb, lock_depth);
return ERR_PTR(-EACCES);
}

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);
}

@@ -363,7 +370,7 @@ 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);
}
--
1.6.2.3


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