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Subject[patch 5/5] mm: filemap: horrid hack to pass __GFP_WRITE for most page cache writers
Date
From: Johannes Weiner <hannes@cmpxchg.org>

This makes every page allocation that results from grabbing a single
page in the page cache pass __GFP_WRITE.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/pagemap.h | 6 ++++--
mm/filemap.c | 8 ++++++--
2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 716875e..3355c9b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -244,12 +244,14 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags);

/*
- * Returns locked page at given index in given cache, creating it if needed.
+ * Returns locked page at given index in given cache, creating it if
+ * needed. XXX: Assumes that page will be dirtied soon!
*/
static inline struct page *grab_cache_page(struct address_space *mapping,
pgoff_t index)
{
- return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
+ return find_or_create_page(mapping, index,
+ mapping_gfp_mask(mapping) | __GFP_WRITE);
}

extern struct page * grab_cache_page_nowait(struct address_space *mapping,
diff --git a/mm/filemap.c b/mm/filemap.c
index a8251a8..e315d46 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1030,6 +1030,7 @@ struct page *
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
{
struct page *page = find_get_page(mapping, index);
+ gfp_t gfp_mask;

if (page) {
if (trylock_page(page))
@@ -1037,7 +1038,8 @@ grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
page_cache_release(page);
return NULL;
}
- page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
+ gfp_mask = (mapping_gfp_mask(mapping) | __GFP_WRITE) & ~__GFP_FS;
+ page = __page_cache_alloc(gfp_mask);
if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
page_cache_release(page);
page = NULL;
@@ -2330,6 +2332,7 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags)
{
int status;
+ gfp_t gfp_mask;
struct page *page;
gfp_t gfp_notmask = 0;
if (flags & AOP_FLAG_NOFS)
@@ -2339,7 +2342,8 @@ repeat:
if (page)
goto found;

- page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
+ gfp_mask = (mapping_gfp_mask(mapping) | __GFP_WRITE) & ~gfp_notmask;
+ page = __page_cache_alloc(gfp_mask);
if (!page)
return NULL;
status = add_to_page_cache_lru(page, mapping, index,
--
1.7.6


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