Commit b84a35be authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Linus Torvalds
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[PATCH] mempool: NOMEMALLOC and NORETRY 



Mempools have 2 problems.

The first is that mempool_alloc can possibly get stuck in __alloc_pages
when they should opt to fail, and take an element from their reserved pool.

The second is that it will happily eat emergency PF_MEMALLOC reserves
instead of going to their reserved pools.

Fix the first by passing __GFP_NORETRY in the allocation calls in
mempool_alloc.  Fix the second by introducing a __GFP_MEMPOOL flag which
directs the page allocator not to allocate from the reserve pool.

Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 8e30f272

include/linux/gfp.h

+4 −2
Original line number Diff line number Diff line
@@ -38,14 +38,16 @@ struct vm_area_struct; 
#define __GFP_NO_GROW	0x2000u	/* Slab internal usage */

#define __GFP_COMP	0x4000u	/* Add compound page metadata */

#define __GFP_ZERO	0x8000u	/* Return zeroed page on success */

#define __GFP_NOMEMALLOC 0x10000u /* Don't use emergency reserves */



#define __GFP_BITS_SHIFT 16	/* Room for 16 __GFP_FOO bits */

#define __GFP_BITS_SHIFT 20	/* Room for 20 __GFP_FOO bits */

#define __GFP_BITS_MASK ((1 << __GFP_BITS_SHIFT) - 1)



/* if you forget to add the bitmask here kernel will crash, period */

#define GFP_LEVEL_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS| \

			__GFP_COLD|__GFP_NOWARN|__GFP_REPEAT| \

			__GFP_NOFAIL|__GFP_NORETRY|__GFP_NO_GROW|__GFP_COMP)

			__GFP_NOFAIL|__GFP_NORETRY|__GFP_NO_GROW|__GFP_COMP| \

			__GFP_NOMEMALLOC)



#define GFP_ATOMIC	(__GFP_HIGH)

#define GFP_NOIO	(__GFP_WAIT)

mm/mempool.c

+7 −2
Original line number Diff line number Diff line
@@ -198,11 +198,16 @@ void * mempool_alloc(mempool_t *pool, unsigned int __nocast gfp_mask) 
	void *element;

	unsigned long flags;

	DEFINE_WAIT(wait);

	int gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);

	int gfp_nowait;



	gfp_mask |= __GFP_NOMEMALLOC;	/* don't allocate emergency reserves */

	gfp_mask |= __GFP_NORETRY;	/* don't loop in __alloc_pages */

	gfp_mask |= __GFP_NOWARN;	/* failures are OK */

	gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);



	might_sleep_if(gfp_mask & __GFP_WAIT);

repeat_alloc:

	element = pool->alloc(gfp_nowait|__GFP_NOWARN, pool->pool_data);

	element = pool->alloc(gfp_nowait, pool->pool_data);

	if (likely(element != NULL))

		return element;

mm/page_alloc.c

+12 −8
Original line number Diff line number Diff line
@@ -799,7 +799,10 @@ __alloc_pages(unsigned int __nocast gfp_mask, unsigned int order, 
	}



	/* This allocation should allow future memory freeing. */

	if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE))) && !in_interrupt()) {



	if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))

			&& !in_interrupt()) {

		if (!(gfp_mask & __GFP_NOMEMALLOC)) {

			/* go through the zonelist yet again, ignoring mins */

			for (i = 0; (z = zones[i]) != NULL; i++) {

				if (!cpuset_zone_allowed(z))
@@ -808,6 +811,7 @@ __alloc_pages(unsigned int __nocast gfp_mask, unsigned int order, 
				if (page)

					goto got_pg;

			}

		}

		goto nopage;

	}