Re: inode_unused list corruption in 2.4.26 - spin_lock problem?

[Trond Myklebust <trond.myklebust@fys.uio.no>]

På lau , 19/06/2004 klokka 20:15, skreiv Marcelo Tosatti:

> The changes between 2.4.25->2.4.26 (which introduce __refile_inode() and 
> the unused_pagecache list) must have something to do with this. 

Here's one question:

Given the fact that in iput(), the inode remains hashed and the
inode->i_state does not change until after we've dropped the inode_lock,
called write_inode_now(), and then retaken the inode_lock, exactly what
is preventing a third party task from grabbing that inode?

(Better still: write_inode_now() itself actually calls __iget(), which
could cause that inode to be plonked right back onto the "inode_in_use"
list if ever refile_inode() gets called.)

So does the following patch help?

Cheers,
  Trond

--- linux-2.4.27-pre3/fs/inode.c.orig	2004-05-20 20:41:41.000000000 -0400
+++ linux-2.4.27-pre3/fs/inode.c	2004-06-19 23:22:29.000000000 -0400
@@ -1200,6 +1200,7 @@ void iput(struct inode *inode)
 		struct super_block *sb = inode->i_sb;
 		struct super_operations *op = NULL;
 
+again:
 		if (inode->i_state == I_CLEAR)
 			BUG();
 
@@ -1241,11 +1242,16 @@ void iput(struct inode *inode)
 				if (!(inode->i_state & (I_DIRTY|I_LOCK))) 
 					__refile_inode(inode);
 				inodes_stat.nr_unused++;
-				spin_unlock(&inode_lock);
-				if (!sb || (sb->s_flags & MS_ACTIVE))
+				if (!sb || (sb->s_flags & MS_ACTIVE)) {
+					spin_unlock(&inode_lock);
 					return;
-				write_inode_now(inode, 1);
-				spin_lock(&inode_lock);
+				}
+				if (inode->i_state & I_DIRTY) {
+					__iget(inode);
+					spin_unlock(&inode_lock);
+					write_inode_now(inode, 1);
+					goto again;
+				}
 				inodes_stat.nr_unused--;
 				list_del_init(&inode->i_hash);
 			}