[PATCH] fix for prune_icache()/forced final iput() races (991114c6) · Commits · 戴 / test

Based on analysis and a patch from Russ Weight <rweight@us.ibm.com> There is a race condition that can occur if an inode is allocated and then released (using iput) during the ->fill_super functions. The race condition is between kswapd and mount. For most filesystems this can only happen in an error path when kswapd is running concurrently. For isofs, however, the error can occur in a more common code path (which is how the bug was found). The logic here is "we want final iput() to free inode *now* instead of letting it sit in cache if fs is going down or had not quite come up". The problem is with kswapd seeing such inodes in the middle of being killed and happily taking over. The clean solution would be to tell kswapd to leave those inodes alone and let our final iput deal with them. I.e. add a new flag (I_FORCED_FREEING), set it before write_inode_now() there and make prune_icache() leave those alone. Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

fs/inode.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -500,7 +500,7 @@ repeat:
		continue;
		if (!test(inode, data))
		continue;
		if (inode->i_state & (I_FREEING\|I_CLEAR)) {
		if (inode->i_state & (I_FREEING\|I_CLEAR\|I_WILL_FREE)) {
		__wait_on_freeing_inode(inode);
		goto repeat;
		}
		@@ -525,7 +525,7 @@ repeat:
		continue;
		if (inode->i_sb != sb)
		continue;
		if (inode->i_state & (I_FREEING\|I_CLEAR)) {
		if (inode->i_state & (I_FREEING\|I_CLEAR\|I_WILL_FREE)) {
		__wait_on_freeing_inode(inode);
		goto repeat;
		}
		@@ -727,7 +727,7 @@ EXPORT_SYMBOL(iunique);
		struct inode igrab(struct inode inode)
		{
		spin_lock(&inode_lock);
		if (!(inode->i_state & I_FREEING))
		if (!(inode->i_state & (I_FREEING\|I_WILL_FREE)))
		__iget(inode);
		else
		/*
		@@ -1024,11 +1024,15 @@ static void generic_forget_inode(struct inode *inode)
		if (!(inode->i_state & (I_DIRTY\|I_LOCK)))
		list_move(&inode->i_list, &inode_unused);
		inodes_stat.nr_unused++;
		if (!sb \|\| (sb->s_flags & MS_ACTIVE)) {
		spin_unlock(&inode_lock);
		if (!sb \|\| (sb->s_flags & MS_ACTIVE))
		return;
		}
		inode->i_state \|= I_WILL_FREE;
		spin_unlock(&inode_lock);
		write_inode_now(inode, 1);
		spin_lock(&inode_lock);
		inode->i_state &= ~I_WILL_FREE;
		inodes_stat.nr_unused--;
		hlist_del_init(&inode->i_hash);
		}

include/linux/fs.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -1025,6 +1025,7 @@ struct super_operations {
		#define I_FREEING 16
		#define I_CLEAR 32
		#define I_NEW 64
		#define I_WILL_FREE 128

		#define I_DIRTY (I_DIRTY_SYNC \| I_DIRTY_DATASYNC \| I_DIRTY_PAGES)

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