fs: protect inode->i_state with inode->i_lock

Protect inode state transitions and validity checks with the
inode->i_lock. This enables us to make inode state transitions
independently of the inode_lock and is the first step to peeling
away the inode_lock from the code.

This requires that __iget() is done atomically with i_state checks
during list traversals so that we don't race with another thread
marking the inode I_FREEING between the state check and grabbing the
reference.

Also remove the unlock_new_inode() memory barrier optimisation
required to avoid taking the inode_lock when clearing I_NEW.
Simplify the code by simply taking the inode->i_lock around the
state change and wakeup. Because the wakeup is no longer tricky,
remove the wake_up_inode() function and open code the wakeup where
necessary.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 7 insertions, 6 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index a2a622e079f0..a1470fda366c 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -902,18 +902,19 @@ static void add_dquot_ref(struct super_block *sb, int type)
 
         spin_lock(&inode_lock);
         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
-                if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
+                spin_lock(&inode->i_lock);
+                if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
+                    !atomic_read(&inode->i_writecount) ||
+                    !dqinit_needed(inode, type)) {
+                        spin_unlock(&inode->i_lock);
                         continue;
+                }
 #ifdef CONFIG_QUOTA_DEBUG
                 if (unlikely(inode_get_rsv_space(inode) > 0))
                         reserved = 1;
 #endif
-                if (!atomic_read(&inode->i_writecount))
-                        continue;
-                if (!dqinit_needed(inode, type))
-                        continue;
-
                 __iget(inode);
+                spin_unlock(&inode->i_lock);
                 spin_unlock(&inode_lock);
 
                 iput(old_inode);