The patch titled
mm: add replace_page_cache_page() function
has been added to the -mm tree. Its filename is
mm-add-replace_page_cache_page-function.patch
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------------------------------------------------------
Subject: mm: add replace_page_cache_page() function
From: Miklos Szeredi <mszeredi@xxxxxxx>
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.
If memory cgroups are enabled, then the memory cgroup charge is also moved
from the old page to the new.
This function is currently used by fuse to move pages into the page cache
on read, instead of copying the page contents.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/fuse/dev.c | 10 ++---
include/linux/memcontrol.h | 4 +-
include/linux/pagemap.h | 1
mm/filemap.c | 65 +++++++++++++++++++++++++++++++++++
mm/memcontrol.c | 4 +-
mm/migrate.c | 2 -
6 files changed, 75 insertions(+), 11 deletions(-)
diff -puN fs/fuse/dev.c~mm-add-replace_page_cache_page-function fs/fuse/dev.c
--- a/fs/fuse/dev.c~mm-add-replace_page_cache_page-function
+++ a/fs/fuse/dev.c
@@ -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))
diff -puN include/linux/memcontrol.h~mm-add-replace_page_cache_page-function include/linux/memcontrol.h
--- a/include/linux/memcontrol.h~mm-add-replace_page_cache_page-function
+++ a/include/linux/memcontrol.h
@@ -96,7 +96,7 @@ extern struct cgroup_subsys_state *mem_c
extern int
mem_cgroup_prepare_migration(struct page *page,
- struct page *newpage, struct mem_cgroup **ptr);
+ struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask);
extern void mem_cgroup_end_migration(struct mem_cgroup *mem,
struct page *oldpage, struct page *newpage, bool migration_ok);
@@ -245,7 +245,7 @@ static inline struct cgroup_subsys_state
static inline int
mem_cgroup_prepare_migration(struct page *page, struct page *newpage,
- struct mem_cgroup **ptr)
+ struct mem_cgroup **ptr, gfp_t gfp_mask)
{
return 0;
}
diff -puN include/linux/pagemap.h~mm-add-replace_page_cache_page-function include/linux/pagemap.h
--- a/include/linux/pagemap.h~mm-add-replace_page_cache_page-function
+++ a/include/linux/pagemap.h
@@ -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:
diff -puN mm/filemap.c~mm-add-replace_page_cache_page-function mm/filemap.c
--- a/mm/filemap.c~mm-add-replace_page_cache_page-function
+++ a/mm/filemap.c
@@ -398,6 +398,71 @@ 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: 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
+ * drops 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;
+ struct mem_cgroup *memcg = NULL;
+
+ VM_BUG_ON(!PageLocked(old));
+ VM_BUG_ON(!PageLocked(new));
+ VM_BUG_ON(new->mapping);
+
+ /*
+ * This is not page migration, but prepare_migration and
+ * end_migration does enough work for charge replacement.
+ *
+ * In the longer term we probably want a specialized function
+ * for moving the charge from old to new in a more efficient
+ * manner.
+ */
+ error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
+ if (error)
+ return error;
+
+ 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();
+ page_cache_release(old);
+ mem_cgroup_end_migration(memcg, old, new, true);
+ } else {
+ mem_cgroup_end_migration(memcg, old, new, false);
+ }
+
+ 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
diff -puN mm/memcontrol.c~mm-add-replace_page_cache_page-function mm/memcontrol.c
--- a/mm/memcontrol.c~mm-add-replace_page_cache_page-function
+++ a/mm/memcontrol.c
@@ -2806,7 +2806,7 @@ static inline int mem_cgroup_move_swap_a
* page belongs to.
*/
int mem_cgroup_prepare_migration(struct page *page,
- struct page *newpage, struct mem_cgroup **ptr)
+ struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask)
{
struct page_cgroup *pc;
struct mem_cgroup *mem = NULL;
@@ -2863,7 +2863,7 @@ int mem_cgroup_prepare_migration(struct
return 0;
*ptr = mem;
- ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, ptr, false, PAGE_SIZE);
+ ret = __mem_cgroup_try_charge(NULL, gfp_mask, ptr, false, PAGE_SIZE);
css_put(&mem->css);/* drop extra refcnt */
if (ret || *ptr == NULL) {
if (PageAnon(page)) {
diff -puN mm/migrate.c~mm-add-replace_page_cache_page-function mm/migrate.c
--- a/mm/migrate.c~mm-add-replace_page_cache_page-function
+++ a/mm/migrate.c
@@ -678,7 +678,7 @@ static int unmap_and_move(new_page_t get
}
/* charge against new page */
- charge = mem_cgroup_prepare_migration(page, newpage, &mem);
+ charge = mem_cgroup_prepare_migration(page, newpage, &mem, GFP_KERNEL);
if (charge == -ENOMEM) {
rc = -ENOMEM;
goto unlock;
_
Patches currently in -mm which might be from mszeredi@xxxxxxx are
origin.patch
linux-next.patch
mm-add-replace_page_cache_page-function.patch
vfs-ignore-error-on-forced-remount.patch
vfs-keep-list-of-mounts-for-each-superblock.patch
vfs-protect-remounting-superblock-read-only.patch
vfs-fs_may_remount_ro-turn-unnecessary-check-into-a-warn_on.patch
mm-add-replace_page_cache_page-function-fix.patch
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