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SubjectRe: VM deadlock


Chris Mason wrote:

> On Wednesday, June 27, 2001 04:27:45 PM +0200 Xuan Baldauf <xuan--lkml@baldauf.org> wrote:
>
> > My linux box suddenly was not availbale using ssh|telnet,
> > but it responded to pings. On console login, I could type
> > "root", but after pressing "return", there was no reaction,
> > and pressing keys did not result in writing them on the
> > screen.
>
> > Warning (Oops_read): Code line not seen, dumping what data
> > is available
> >
> >>> EIP; c012839c <deactivate_page+e94/2618> <=====
> > Trace; c0128ef5 <deactivate_page+19ed/2618>
> > Trace; c012905e <deactivate_page+1b56/2618>
> > Trace; c0129d05 <__alloc_pages+1cd/280>
> > Trace; c0129b36 <_alloc_pages+16/18>
> > Trace; c012a425 <free_pages+611/1cac>
> > Trace; c0120198 <vmtruncate+1c4/878>
> > Trace; c01201f5 <vmtruncate+221/878>
> > Trace; c0120550 <vmtruncate+57c/878>
>
> > I had a probably similar|connected problem (but with no
> > "ping" responding) with linux-2.4.5-pre3, described here:
> > http://lists.omnipotent.net/reiserfs/200106/msg00214.html
> >
> > Linux router 2.4.6-pre5 #3 Tue Jun 26 23:36:26 CEST 2001
>
> Sounds like a deadlock andrea recently found.
>
> Could you please give this a try:
>
> diff -urN 2.4.6pre5aa1/include/linux/swap.h 2.4.6pre5aa1-backout-page_launder/include/linux/swap.h
> --- 2.4.6pre5aa1/include/linux/swap.h Sun Jun 24 02:06:13 2001
> +++ 2.4.6pre5aa1-backout-page_launder/include/linux/swap.h Sun Jun 24 21:37:12 2001
> @@ -205,16 +205,6 @@
> page->zone->inactive_dirty_pages++; \
> }
>
> -/* Like the above, but add us after the bookmark. */
> -#define add_page_to_inactive_dirty_list_marker(page) { \
> - DEBUG_ADD_PAGE \
> - ZERO_PAGE_BUG \
> - SetPageInactiveDirty(page); \
> - list_add(&(page)->lru, marker_lru); \
> - nr_inactive_dirty_pages++; \
> - page->zone->inactive_dirty_pages++; \
> -}
> -
> #define add_page_to_inactive_clean_list(page) { \
> DEBUG_ADD_PAGE \
> ZERO_PAGE_BUG \
> diff -urN 2.4.6pre5aa1/mm/vmscan.c 2.4.6pre5aa1-backout-page_launder/mm/vmscan.c
> --- 2.4.6pre5aa1/mm/vmscan.c Sun Jun 24 01:41:09 2001
> +++ 2.4.6pre5aa1-backout-page_launder/mm/vmscan.c Sun Jun 24 21:37:11 2001
> @@ -407,7 +407,7 @@
> /**
> * page_launder - clean dirty inactive pages, move to inactive_clean list
> * @gfp_mask: what operations we are allowed to do
> - * @sync: are we allowed to do synchronous IO in emergencies ?
> + * @sync: should we wait synchronously for the cleaning of pages
> *
> * When this function is called, we are most likely low on free +
> * inactive_clean pages. Since we want to refill those pages as
> @@ -426,61 +426,23 @@
> #define MAX_LAUNDER (4 * (1 << page_cluster))
> #define CAN_DO_IO (gfp_mask & __GFP_IO)
> #define CAN_DO_BUFFERS (gfp_mask & __GFP_BUFFER)
> -#define marker_lru (&marker_page_struct.lru)
> int page_launder(int gfp_mask, int sync)
> {
> - static int cannot_free_pages;
> int launder_loop, maxscan, cleaned_pages, maxlaunder;
> struct list_head * page_lru;
> struct page * page;
>
> - /* Our bookmark of where we are in the inactive_dirty list. */
> - struct page marker_page_struct = { zone: NULL };
> -
> launder_loop = 0;
> maxlaunder = 0;
> cleaned_pages = 0;
>
> dirty_page_rescan:
> spin_lock(&pagemap_lru_lock);
> - /*
> - * By not scanning all inactive dirty pages we'll write out
> - * really old dirty pages before evicting newer clean pages.
> - * This should cause some LRU behaviour if we have a large
> - * amount of inactive pages (due to eg. drop behind).
> - *
> - * It also makes us accumulate dirty pages until we have enough
> - * to be worth writing to disk without causing excessive disk
> - * seeks and eliminates the infinite penalty clean pages incurred
> - * vs. dirty pages.
> - */
> - maxscan = nr_inactive_dirty_pages / 4;
> - if (launder_loop)
> - maxscan *= 2;
> - list_add_tail(marker_lru, &inactive_dirty_list);
> - for (;;) {
> - page_lru = marker_lru->prev;
> - if (page_lru == &inactive_dirty_list)
> - break;
> - if (--maxscan < 0)
> - break;
> - if (!free_shortage())
> - break;
> -
> + maxscan = nr_inactive_dirty_pages;
> + while ((page_lru = inactive_dirty_list.prev) != &inactive_dirty_list &&
> + maxscan-- > 0) {
> page = list_entry(page_lru, struct page, lru);
>
> - /* Move the bookmark backwards.. */
> - list_del(marker_lru);
> - list_add_tail(marker_lru, page_lru);
> -
> - /* Don't waste CPU if chances are we cannot free anything. */
> - if (launder_loop && maxlaunder < 0 && cannot_free_pages)
> - break;
> -
> - /* Skip other people's marker pages. */
> - if (!page->zone)
> - continue;
> -
> /* Wrong page on list?! (list corruption, should not happen) */
> if (!PageInactiveDirty(page)) {
> printk("VM: page_launder, wrong page on list.\n");
> @@ -492,6 +454,7 @@
>
> /* Page is or was in use? Move it to the active list. */
> if (PageReferenced(page) || page->age > 0 ||
> + page->zone->free_pages > page->zone->pages_high ||
> (!page->buffers && page_count(page) > 1) ||
> page_ramdisk(page)) {
> del_page_from_inactive_dirty_list(page);
> @@ -501,9 +464,11 @@
>
> /*
> * The page is locked. IO in progress?
> - * Skip the page, we'll take a look when it unlocks.
> + * Move it to the back of the list.
> */
> if (TryLockPage(page)) {
> + list_del(page_lru);
> + list_add(page_lru, &inactive_dirty_list);
> continue;
> }
>
> @@ -517,8 +482,10 @@
> if (!writepage)
> goto page_active;
>
> - /* First time through? Skip the page. */
> + /* First time through? Move it to the back of the list */
> if (!launder_loop || !CAN_DO_IO) {
> + list_del(page_lru);
> + list_add(page_lru, &inactive_dirty_list);
> UnlockPage(page);
> continue;
> }
> @@ -531,8 +498,6 @@
> writepage(page);
> page_cache_release(page);
>
> - maxlaunder--;
> -
> /* And re-start the thing.. */
> spin_lock(&pagemap_lru_lock);
> continue;
> @@ -560,9 +525,9 @@
> spin_unlock(&pagemap_lru_lock);
>
> /* Will we do (asynchronous) IO? */
> - if (launder_loop && maxlaunder-- == 0 && sync)
> + if (launder_loop && maxlaunder == 0 && sync)
> wait = 2; /* Synchrounous IO */
> - else if (launder_loop && maxlaunder > 0)
> + else if (launder_loop && maxlaunder-- > 0)
> wait = 1; /* Async IO */
> else
> wait = 0; /* No IO */
> @@ -579,7 +544,7 @@
>
> /* The buffers were not freed. */
> if (!clearedbuf) {
> - add_page_to_inactive_dirty_list_marker(page);
> + add_page_to_inactive_dirty_list(page);
>
> /* The page was only in the buffer cache. */
> } else if (!page->mapping) {
> @@ -635,8 +600,6 @@
> UnlockPage(page);
> }
> }
> - /* Remove our marker. */
> - list_del(marker_lru);
> spin_unlock(&pagemap_lru_lock);
>
> /*
> @@ -652,29 +615,16 @@
> */
> if ((CAN_DO_IO || CAN_DO_BUFFERS) && !launder_loop && free_shortage()) {
> launder_loop = 1;
> - /*
> - * If we, or the previous process running page_launder(),
> - * managed to free any pages we never do synchronous IO.
> - */
> - if (cleaned_pages || !cannot_free_pages)
> + /* If we cleaned pages, never do synchronous IO. */
> + if (cleaned_pages)
> sync = 0;
> - /* Else, do synchronous IO (if we are allowed to). */
> - else if (sync)
> - sync = 1;
> /* We only do a few "out of order" flushes. */
> maxlaunder = MAX_LAUNDER;
> - /* Let bdflush take care of the rest. */
> + /* Kflushd takes care of the rest. */
> wakeup_bdflush(0);
> goto dirty_page_rescan;
> }
>
> - /*
> - * If we failed to free pages (because all pages are dirty)
> - * we remember this for the next time. This will prevent us
> - * from wasting too much CPU here.
> - */
> - cannot_free_pages = !cleaned_pages;
> -
> /* Return the number of pages moved to the inactive_clean list. */
> return cleaned_pages;
> }
> @@ -899,7 +849,7 @@
> * list, so this is a relatively cheap operation.
> */
> if (free_shortage()) {
> - ret += page_launder(gfp_mask, 1);
> + ret += page_launder(gfp_mask, user);
> shrink_dcache_memory(DEF_PRIORITY, gfp_mask);
> shrink_icache_memory(DEF_PRIORITY, gfp_mask);
> }
>

Thank you, Chris.

I am currently compiling. For now, it does not seem to look like a reiserfs-specific bug. Because I do
not know how to trigger the bug, I do not know wether and how it will happen again. The deadlock
described occured within 1 day uptime of my linux-2.4.5-pre5 kernel, so if I do not report it again
within a week or so, this fix above might be the right one.

Xuân.


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