On Mon, 17 Dec 2007 12:13:22 +0000 richard <[email protected]> wrote:
> fix lockup in when calling drop_caches
>
> calling /proc/sys/vm/drop_caches can hang due to a AB/BA lock dependency
> between j_list_lock and the inode_lock. This patch moves the redirtying of the buffer head out
> from under the j_list_lock.
>
> based on a suggestion by Andrew Morton.
>
Oh boy. Do we really want to add all this stuff to JBD just for
drop_caches which is a silly root-only broken-in-22-other-ways thing?
Michael, might your convert-inode-lists-to-tree patches eliminate the need
for taking inode_lock in drop_pagecache_sb()? Probably not, as it uses an
rbtree. It would have been possible if it was using a radix-tree, I
suspect..
> -void __journal_unfile_buffer(struct journal_head *jh)
> +void __journal_unfile_buffer(struct journal_head *jh,
> + struct buffer_head **dirty_bh)
> {
> - __journal_temp_unlink_buffer(jh);
> + __journal_temp_unlink_buffer(jh, dirty_bh);
> jh->b_transaction = NULL;
> }
I suspect the code would end up simpler if __journal_unfile_buffer() were
to take an additional ref on the bh which it placed at *dirty_bh.
Callers of __journal_unfile_buffer() could then call
void handle_dirty_bh(struct buffer_head *bh)
{
if (bh) {
jbd_mark_buffer_dirty(bh);
put_bh(bh);
}
}
?
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