[patch 3/9] no PF_MEMALLOC tinkering

Nick Piggin
2005-04-12T13:50:50Z

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3/9

--
SUSE Labs, Novell Inc.

[-- Attachment #2: no-PF_MEMALLOC-tinkering.patch --]
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PF_MEMALLOC is really not a tool for tinkering. It is pretty specifically
used to prevent recursion into page reclaim, and to prevent low memory
deadlocks.

The mm/swap_state.c code was the only legitimate tinkerer. Its concern
was addressed by the previous patch.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>

Index: linux-2.6/mm/swap_state.c
===================================================================
--- linux-2.6.orig/mm/swap_state.c 2005-04-12 22:05:44.000000000 +1000
+++ linux-2.6/mm/swap_state.c 2005-04-12 22:26:12.000000000 +1000
@@ -143,7 +143,6 @@ void __delete_from_swap_cache(struct pag
int add_to_swap(struct page * page)
{
swp_entry_t entry;
- int pf_flags;
int err;

if (!PageLocked(page))
@@ -154,30 +153,11 @@ int add_to_swap(struct page * page)
if (!entry.val)
return 0;

- /* Radix-tree node allocations are performing
- * GFP_ATOMIC allocations under PF_MEMALLOC.
- * They can completely exhaust the page allocator.
- *
- * So PF_MEMALLOC is dropped here. This causes the slab
- * allocations to fail earlier, so radix-tree nodes will
- * then be allocated from the mempool reserves.
- *
- * We're still using __GFP_HIGH for radix-tree node
- * allocations, so some of the emergency pools are available,
- * just not all of them.
- */
-
- pf_flags = current->flags;
- current->flags &= ~PF_MEMALLOC;
-
/*
* Add it to the swap cache and mark it dirty
*/
err = __add_to_swap_cache(page, entry, GFP_ATOMIC|__GFP_NOWARN);

- if (pf_flags & PF_MEMALLOC)
- current->flags |= PF_MEMALLOC;
-
switch (err) {
case 0: /* Success */
SetPageUptodate(page);
Index: linux-2.6/drivers/md/dm-crypt.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-crypt.c 2005-04-12 22:05:44.000000000 +1000
+++ linux-2.6/drivers/md/dm-crypt.c 2005-04-12 22:26:12.000000000 +1000
@@ -331,25 +331,14 @@ crypt_alloc_buffer(struct crypt_config *
struct bio *bio;
unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
int gfp_mask = GFP_NOIO | __GFP_HIGHMEM;
- unsigned long flags = current->flags;
unsigned int i;

- /*
- * Tell VM to act less aggressively and fail earlier.
- * This is not necessary but increases throughput.
- * FIXME: Is this really intelligent?
- */
- current->flags &= ~PF_MEMALLOC;
-
if (base_bio)
bio = bio_clone(base_bio, GFP_NOIO);
else
bio = bio_alloc(GFP_NOIO, nr_iovecs);
- if (!bio) {
- if (flags & PF_MEMALLOC)
- current->flags |= PF_MEMALLOC;
+ if (!bio)
return NULL;
- }

/* if the last bio was not complete, continue where that one ended */
bio->bi_idx = *bio_vec_idx;
@@ -386,9 +375,6 @@ crypt_alloc_buffer(struct crypt_config *
size -= bv->bv_len;
}

- if (flags & PF_MEMALLOC)
- current->flags |= PF_MEMALLOC;
-
if (!bio->bi_size) {
bio_put(bio);
return NULL;
Index: linux-2.6/fs/mpage.c
===================================================================
--- linux-2.6.orig/fs/mpage.c 2005-04-12 22:05:44.000000000 +1000
+++ linux-2.6/fs/mpage.c 2005-04-12 22:26:12.000000000 +1000
@@ -105,11 +105,6 @@ mpage_alloc(struct block_device *bdev,

bio = bio_alloc(gfp_flags, nr_vecs);

- if (bio == NULL && (current->flags & PF_MEMALLOC)) {
- while (!bio && (nr_vecs /= 2))
- bio = bio_alloc(gfp_flags, nr_vecs);
- }
-
if (bio) {
bio->bi_bdev = bdev;
bio->bi_sector = first_sector;