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Subject[PATCH] VFS bugfix: two read_inode() calles without clear_inode() call between
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Dear VFS developers,

is it possible to review/comment/apply the patch which fixes a severe
VFS bug which screws up JFFS2?

(the third attempt).

The problem description:
~~~~~~~~~~~~~~~~~~~~~~

prune_icache() removes inodes from the inode hash (inode->i_hash) and
drops the node_lock spinlock. If at that moment iget() is called, we end
up with the situation when VFS calls ->read_inode() twice for the same
inode without calling ->clear_inode() between. This happens despite of
the I_FREEING inode state because the inode is already removed from the
hash by the time find_inode_fast() is invoked.

The fix is: do not remove the inode from the hash too early.

The following patch fixes the problem. It was tested with JFFS2 (only)
and works perfectly.

Comments?



Signed-off-by: Artem B. Bityuckiy <dedekind@infradead.org>


diff -auNrp linux-2.6.11.5/fs/inode.c linux-2.6.11.5_fixed/fs/inode.c
--- linux-2.6.11.5/fs/inode.c 2005-03-19 09:35:04.000000000 +0300
+++ linux-2.6.11.5_fixed/fs/inode.c 2005-04-18 17:54:16.000000000
+0400
@@ -284,6 +284,12 @@ static void dispose_list(struct list_hea
if (inode->i_data.nrpages)
truncate_inode_pages(&inode->i_data, 0);
clear_inode(inode);
+
+ spin_lock(&inode_lock);
+ hlist_del_init(&inode->i_hash);
+ list_del_init(&inode->i_sb_list);
+ spin_unlock(&inode_lock);
+
destroy_inode(inode);
nr_disposed++;
}
@@ -319,8 +325,6 @@ static int invalidate_list(struct list_h
inode = list_entry(tmp, struct inode, i_sb_list);
invalidate_inode_buffers(inode);
if (!atomic_read(&inode->i_count)) {
- hlist_del_init(&inode->i_hash);
- list_del(&inode->i_sb_list);
list_move(&inode->i_list, dispose);
inode->i_state |= I_FREEING;
count++;
@@ -455,8 +459,6 @@ static void prune_icache(int nr_to_scan)
if (!can_unuse(inode))
continue;
}
- hlist_del_init(&inode->i_hash);
- list_del_init(&inode->i_sb_list);
list_move(&inode->i_list, &freeable);
inode->i_state |= I_FREEING;
nr_pruned++;
--
Best Regards,
Artem B. Bityuckiy,
St.-Petersburg, Russia.

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