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Date: Fri, 07 Jan 2011 19:22:41 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: akpm@...ux-foundation.org
CC: minchan.kim@...il.com, kamezawa.hiroyu@...fujitsu.com,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] mm: add replace_page_cache_page() function
Here's an updated patch, addressing the review comments.
Hiroyuki-san, can you please review the newly introduced
mem_cgroup_replace_cache_page(), as I'm not fully familiar with the
memory cgroup code.
Thanks,
Miklos
---
From: Miklos Szeredi <mszeredi@...e.cz>
Subject: mm: add replace_page_cache_page() function
This function basically does:
remove_from_page_cache(old);
page_cache_release(old);
add_to_page_cache_locked(new);
Except it does this atomically, so there's no possibility for the
"add" to fail because of a race.
This is used by fuse to move pages into the page cache.
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
---
fs/fuse/dev.c | 10 +++------
include/linux/memcontrol.h | 8 +++++++
include/linux/pagemap.h | 1
mm/filemap.c | 50 +++++++++++++++++++++++++++++++++++++++++++++
mm/memcontrol.c | 38 ++++++++++++++++++++++++++++++++++
5 files changed, 101 insertions(+), 6 deletions(-)
Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c 2011-01-07 17:53:39.000000000 +0100
+++ linux-2.6/mm/filemap.c 2011-01-07 19:14:45.000000000 +0100
@@ -390,6 +390,56 @@ int filemap_write_and_wait_range(struct
EXPORT_SYMBOL(filemap_write_and_wait_range);
/**
+ * replace_page_cache_page - replace a pagecache page with a new one
+ * @old: page to be replaced
+ * @new: page to replace with
+ * @gfp_mask: page allocation mode
+ *
+ * This function replaces a page in the pagecache with a new one. On
+ * success it acquires the pagecache reference for the new page and
+ * drop it for the old page. Both the old and new pages must be
+ * locked. This function does not add the new page to the LRU, the
+ * caller must do that.
+ *
+ * The remove + add is atomic. The only way this function can fail is
+ * memory allocation failure.
+ */
+int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
+{
+ int error;
+
+ VM_BUG_ON(!PageLocked(old));
+ VM_BUG_ON(!PageLocked(new));
+ VM_BUG_ON(new->mapping);
+
+ error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
+ if (!error) {
+ struct address_space *mapping = old->mapping;
+ pgoff_t offset = old->index;
+
+ page_cache_get(new);
+ new->mapping = mapping;
+ new->index = offset;
+
+ spin_lock_irq(&mapping->tree_lock);
+ __remove_from_page_cache(old);
+ error = radix_tree_insert(&mapping->page_tree, offset, new);
+ BUG_ON(error);
+ mapping->nrpages++;
+ __inc_zone_page_state(new, NR_FILE_PAGES);
+ if (PageSwapBacked(new))
+ __inc_zone_page_state(new, NR_SHMEM);
+ spin_unlock_irq(&mapping->tree_lock);
+ radix_tree_preload_end();
+ mem_cgroup_replace_cache_page(old, new);
+ page_cache_release(old);
+ }
+
+ return error;
+}
+EXPORT_SYMBOL_GPL(replace_page_cache_page);
+
+/**
* add_to_page_cache_locked - add a locked page to the pagecache
* @page: page to add
* @mapping: the page's address_space
Index: linux-2.6/include/linux/pagemap.h
===================================================================
--- linux-2.6.orig/include/linux/pagemap.h 2011-01-07 17:53:39.000000000 +0100
+++ linux-2.6/include/linux/pagemap.h 2011-01-07 19:14:45.000000000 +0100
@@ -457,6 +457,7 @@ int add_to_page_cache_lru(struct page *p
pgoff_t index, gfp_t gfp_mask);
extern void remove_from_page_cache(struct page *page);
extern void __remove_from_page_cache(struct page *page);
+int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
/*
* Like add_to_page_cache_locked, but used to add newly allocated pages:
Index: linux-2.6/fs/fuse/dev.c
===================================================================
--- linux-2.6.orig/fs/fuse/dev.c 2011-01-07 17:53:39.000000000 +0100
+++ linux-2.6/fs/fuse/dev.c 2011-01-07 19:14:45.000000000 +0100
@@ -737,14 +737,12 @@ static int fuse_try_move_page(struct fus
if (WARN_ON(PageMlocked(oldpage)))
goto out_fallback_unlock;
- remove_from_page_cache(oldpage);
- page_cache_release(oldpage);
-
- err = add_to_page_cache_locked(newpage, mapping, index, GFP_KERNEL);
+ err = replace_page_cache_page(oldpage, newpage, GFP_KERNEL);
if (err) {
- printk(KERN_WARNING "fuse_try_move_page: failed to add page");
- goto out_fallback_unlock;
+ unlock_page(newpage);
+ return err;
}
+
page_cache_get(newpage);
if (!(buf->flags & PIPE_BUF_FLAG_LRU))
Index: linux-2.6/include/linux/memcontrol.h
===================================================================
--- linux-2.6.orig/include/linux/memcontrol.h 2011-01-07 17:53:39.000000000 +0100
+++ linux-2.6/include/linux/memcontrol.h 2011-01-07 19:14:45.000000000 +0100
@@ -95,6 +95,9 @@ mem_cgroup_prepare_migration(struct page
extern void mem_cgroup_end_migration(struct mem_cgroup *mem,
struct page *oldpage, struct page *newpage);
+extern void mem_cgroup_replace_cache_page(struct page *oldpage,
+ struct page *newpage);
+
/*
* For memory reclaim.
*/
@@ -236,6 +239,11 @@ static inline void mem_cgroup_end_migrat
{
}
+static inline void mem_cgroup_replace_cache_page(struct page *oldpage,
+ struct page *newpage)
+{
+}
+
static inline int mem_cgroup_get_reclaim_priority(struct mem_cgroup *mem)
{
return 0;
Index: linux-2.6/mm/memcontrol.c
===================================================================
--- linux-2.6.orig/mm/memcontrol.c 2011-01-07 17:53:39.000000000 +0100
+++ linux-2.6/mm/memcontrol.c 2011-01-07 19:20:41.000000000 +0100
@@ -2905,6 +2905,44 @@ void mem_cgroup_end_migration(struct mem
}
/*
+ * This function moves the charge from oldpage to newpage. The new
+ * page must not be already charged.
+ */
+void mem_cgroup_replace_cache_page(struct page *oldpage, struct page *newpage)
+{
+ struct page_cgroup *old_pc;
+ struct page_cgroup *new_pc;
+ struct mem_cgroup *mem;
+
+ if (mem_cgroup_disabled())
+ return;
+
+ old_pc = lookup_page_cgroup(oldpage);
+ lock_page_cgroup(old_pc);
+ if (!PageCgroupUsed(old_pc)) {
+ unlock_page_cgroup(old_pc);
+ return;
+ }
+
+ mem = old_pc->mem_cgroup;
+ css_get(&mem->css);
+ ClearPageCgroupUsed(old_pc);
+ unlock_page_cgroup(old_pc);
+
+ new_pc = lookup_page_cgroup(newpage);
+ lock_page_cgroup(new_pc);
+ BUG_ON(PageCgroupUsed(new_pc));
+
+ new_pc->mem_cgroup = mem;
+ smp_wmb();
+ SetPageCgroupCache(new_pc);
+ SetPageCgroupUsed(new_pc);
+ unlock_page_cgroup(new_pc);
+ css_put(&mem->css);
+}
+
+
+/*
* A call to try to shrink memory usage on charge failure at shmem's swapin.
* Calling hierarchical_reclaim is not enough because we should update
* last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
--
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