[Bug 238813] drop_caches lockdep warning

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https://bugzilla.redhat.com/show_bug.cgi?id=238813


Harshula Jayasuriya <harshula at redhat.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |harshula at redhat.com




--- Comment #4 from Harshula Jayasuriya <harshula at redhat.com>  2009-04-14 04:09:51 EDT ---
Hi,

Looks like this has been fixed in TOT:
-------------------------------------------------
commit eccb95cee4f0d56faa46ef22fb94dd4a3578d3eb
Author: Jan Kara <jack at suse.cz>
Date:   Tue Apr 29 00:59:37 2008 -0700

    vfs: fix lock inversion in drop_pagecache_sb()

    Fix longstanding lock inversion in drop_pagecache_sb by dropping inode_lock
    before calling __invalidate_mapping_pages().  We just have to make sure
inode
    won't go away from under us by keeping reference to it and putting the
    reference only after we have safely resumed the scan of the inode list.  A
bit
    tricky but not too bad...

    Signed-off-by: Jan Kara <jack at suse.cz>
    Cc: Fengguang Wu <wfg at mail.ustc.edu.cn>
    Cc: David Chinner <dgc at sgi.com>
    Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index e2c6b65..50f9087 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -14,15 +14,21 @@ int sysctl_drop_caches;

 static void drop_pagecache_sb(struct super_block *sb)
 {
- struct inode *inode;
+ struct inode *inode, *toput_inode = NULL;

  spin_lock(&inode_lock);
  list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
   if (inode->i_state & (I_FREEING|I_WILL_FREE))
    continue;
+  __iget(inode);
+  spin_unlock(&inode_lock);
   __invalidate_mapping_pages(inode->i_mapping, 0, -1, true);
+  iput(toput_inode);
+  toput_inode = inode;
+  spin_lock(&inode_lock);
  }
  spin_unlock(&inode_lock);
+ iput(toput_inode);
 }

 static void drop_pagecache(void)
-------------------------------------------------

Regards,
Harshula

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