2003-03-25 17:28:34

by Stephen C. Tweedie

Subject: [Patch 2/8] 2.4: Fix for enormous numbers of buffers on BUF_LOCKED

Buffer_head syncing places BUF_DIRTY buffers on the BUF_LOCKED, but
buffers can stay there indefinitely, upsetting buffer accounting. The
symptoms are benign, mostly just nonsensical numbers in alt-sysrq-m
output, but it's pretty cheap to clean these up in kupdated
nonetheless, just by refiling any unlocked buffers which happen to be
at the head of the BUF_LOCKED list. (We stop at the first locked
buffer rather than walking the whole list, avoiding walking any
buffers more than once.)

--- linux-2.4-ext3push/fs/buffer.c.=K0001=.orig 2003-03-25 10:59:15.000000000 +0000
+++ linux-2.4-ext3push/fs/buffer.c 2003-03-25 10:59:15.000000000 +0000
@@ -2958,6 +2958,30 @@ int bdflush(void *startup)
}
}

+
+/*
+ * Do some IO post-processing here!!!
+ */
+void do_io_postprocessing(void)
+{
+ int i;
+ struct buffer_head *bh, *next;
+
+ spin_lock(&lru_list_lock);
+ bh = lru_list[BUF_LOCKED];
+ if (bh) {
+ for (i = nr_buffers_type[BUF_LOCKED]; i-- > 0; bh = next) {
+ next = bh->b_next_free;
+
+ if (!buffer_locked(bh))
+ __refile_buffer(bh);
+ else
+ break;
+ }
+ }
+ spin_unlock(&lru_list_lock);
+}
+
/*
* This is the kernel update daemon. It was used to live in userspace
* but since it's need to run safely we want it unkillable by mistake.
@@ -3009,6 +3033,7 @@ int kupdate(void *startup)
#ifdef DEBUG
printk(KERN_DEBUG "kupdate() activated...\n");
#endif
+ do_io_postprocessing();
sync_old_buffers();
run_task_queue(&tq_disk);
}

2003-03-25 17:37:05

by Christoph Hellwig

Subject: Re: [Patch 2/8] 2.4: Fix for enormous numbers of buffers on BUF_LOCKED

On Tue, Mar 25, 2003 at 05:39:40PM +0000, Stephen Tweedie wrote:
> +/*
> + * Do some IO post-processing here!!!

Do we really need to shout at each other !?!?!?!?!?