lkml.org 
[lkml]   [2011]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v3] mm: add replace_page_cache_page() function
    On Thu, 13 Jan 2011 14:35:09 +0100
    Miklos Szeredi <miklos@szeredi.hu> wrote:

    > > Seems nicer. But you didn't fixed the caller of prepare_migraton()
    > > in mm/migrate.c (I think this is the only caller..)
    > >
    > > please modify it, too.
    >
    > Right you are. Thanks for the review.
    >
    > Updated patch attached.
    >
    > Thanks,
    > Miklos
    > ---
    >
    >
    > From: Miklos Szeredi <mszeredi@suse.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@suse.cz>
    > ---
    > 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(-)
    >
    > Index: linux-2.6/mm/filemap.c
    > ===================================================================
    > --- linux-2.6.orig/mm/filemap.c 2011-01-12 15:28:56.000000000 +0100
    > +++ linux-2.6/mm/filemap.c 2011-01-13 13:37:41.000000000 +0100
    > @@ -387,6 +387,71 @@ 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
    > Index: linux-2.6/include/linux/pagemap.h
    > ===================================================================
    > --- linux-2.6.orig/include/linux/pagemap.h 2011-01-12 15:28:56.000000000 +0100
    > +++ linux-2.6/include/linux/pagemap.h 2011-01-13 13:37:41.000000000 +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 2011-01-12 15:28:56.000000000 +0100
    > +++ linux-2.6/fs/fuse/dev.c 2011-01-13 13:37:41.000000000 +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 2011-01-13 13:37:40.000000000 +0100
    > +++ linux-2.6/include/linux/memcontrol.h 2011-01-13 13:37:41.000000000 +0100
    > @@ -91,7 +91,7 @@ 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);
    >
    > @@ -225,7 +225,7 @@ 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;
    > }
    > Index: linux-2.6/mm/memcontrol.c
    > ===================================================================
    > --- linux-2.6.orig/mm/memcontrol.c 2011-01-13 13:37:40.000000000 +0100
    > +++ linux-2.6/mm/memcontrol.c 2011-01-13 13:37:41.000000000 +0100
    > @@ -2767,7 +2767,7 @@ 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;
    > @@ -2823,7 +2823,7 @@ int mem_cgroup_prepare_migration(struct
    > return 0;
    >
    > *ptr = mem;
    > - ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, ptr, false);
    > + ret = __mem_cgroup_try_charge(NULL, gfp_mask, ptr, false);
    > css_put(&mem->css);/* drop extra refcnt */
    > if (ret || *ptr == NULL) {
    > if (PageAnon(page)) {
    > Index: linux-2.6/mm/migrate.c
    > ===================================================================
    > --- linux-2.6.orig/mm/migrate.c 2011-01-13 13:37:40.000000000 +0100
    > +++ linux-2.6/mm/migrate.c 2011-01-13 13:38:55.000000000 +0100
    > @@ -657,7 +657,7 @@ 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;
    This patch looks good and I want to ack, but this patch can conflict with patches
    in https://lkml.org/lkml/2011/1/11/10 and https://lkml.org/lkml/2011/1/11/65.
    So I think you'd better coordinate with Minchan.

    Thanks,
    Daisuke Nishimura.


    \
     
     \ /
      Last update: 2011-01-14 02:07    [W:0.046 / U:90.528 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site