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Subject[PATCH] blindingly stupid 2.2 VM bug
Hi Alan,

here's a fix for a blindingly stupid bug that's been in
2.2 for ages (and which I've warned you about a few times
in the last 6 months, and which I've even sent some patches
for).

This patch should make 2.2 VM a bit more stable and should
also fix the complaints from people who's system gets
flooded by "VM: do_try_to_free_pages failed for process XXX"

It's against something suspiciously like 2.2.18-pre15, so
chances are it'll apply cleanly.

regards,

Rik
--
Hollywood goes for world dumbination,
Trailer at 11.

http://www.conectiva.com/ http://www.surriel.com/



--- ../rpm/BUILD/linux/mm/vmscan.c Sat Nov 18 21:56:50 2000
+++ linux/mm/vmscan.c Sun Nov 5 19:36:23 2000
@@ -17,7 +17,6 @@
#include <linux/smp_lock.h>
#include <linux/pagemap.h>
#include <linux/init.h>
-#include <linux/bigmem.h>

#include <asm/pgtable.h>

@@ -61,8 +60,7 @@

if (PageReserved(page_map)
|| PageLocked(page_map)
- || ((gfp_mask & __GFP_DMA) && !PageDMA(page_map))
- || (!(gfp_mask & __GFP_BIGMEM) && PageBIGMEM(page_map)))
+ || ((gfp_mask & __GFP_DMA) && !PageDMA(page_map)))
return 0;

/*
@@ -156,9 +154,6 @@
if (!entry)
return 0; /* No swap space left */

- if (!(page_map = prepare_bigmem_swapout(page_map)))
- goto out_swap_free;
-
vma->vm_mm->rss--;
tsk->nswap++;
set_pte(page_table, __pte(entry));
@@ -170,14 +165,10 @@
set_bit(PG_locked, &page_map->flags);

/* OK, do a physical asynchronous write to swap. */
- rw_swap_page(WRITE, entry, (char *) page_address(page_map), 0);
+ rw_swap_page(WRITE, entry, (char *) page, 0);

__free_page(page_map);
return 1;
-
- out_swap_free:
- swap_free(entry);
- return 0;
}

/*
@@ -400,13 +391,14 @@
{
int priority;
int count = SWAP_CLUSTER_MAX;
+ int loopcount = count;

lock_kernel();

/* Always trim SLAB caches when memory gets low. */
kmem_cache_reap(gfp_mask);

- priority = 5;
+ priority = 6;
do {
while (shrink_mmap(priority, gfp_mask)) {
if (!--count)
@@ -428,12 +420,21 @@
}

shrink_dcache_memory(priority, gfp_mask);
- } while (--priority > 0);
+
+ /* Only lower priority if we didn't make progress. */
+ if (count == loopcount) {
+ priority--;
+ }
+ loopcount = count;
+ } while (priority > 0);
done:
unlock_kernel();

- /* Return success if we freed a page. */
- return priority > 0;
+ /* Return success if we have enough free memory or we freed a page. */
+ if (nr_free_pages > freepages.low)
+ return 1;
+
+ return count < SWAP_CLUSTER_MAX;
}

/*
@@ -505,22 +506,23 @@
* the processes needing more memory will wake us
* up on a more timely basis.
*/
- interruptible_sleep_on(&kswapd_wait);
+ interruptible_sleep_on_timeout(&kswapd_wait, HZ);

- /*
- * In 2.2.x-bigmem kswapd is critical to provide GFP_ATOMIC
- * allocations (not GFP_BIGMEM ones).
- */
- while (nr_free_pages - nr_free_bigpages < freepages.high)
- {
- if (try_to_free_pages(GFP_KSWAPD))
+ if (nr_free_pages < freepages.low) {
+ while (nr_free_pages < freepages.high)
{
- if (tsk->need_resched)
- schedule();
- continue;
+ if (try_to_free_pages(GFP_KSWAPD))
+ {
+ if (tsk->need_resched)
+ schedule();
+ continue;
+ }
+ tsk->state = TASK_INTERRUPTIBLE;
+ schedule_timeout(10*HZ);
}
- tsk->state = TASK_INTERRUPTIBLE;
- schedule_timeout(10*HZ);
+ } else if (nr_free_pages < freepages.high) {
+ /* Background scanning. */
+ try_to_free_pages(GFP_KSWAPD);
}
}
}
-
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