On Thu, Dec 16, 2010 at 12:49 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > 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. > > This is used by fuse to move pages into the page cache. Please write down why fuse need this new atomic function in description. > > Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx> > --- > fs/fuse/dev.c | 10 ++++------ > include/linux/pagemap.h | 1 + > mm/filemap.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 46 insertions(+), 6 deletions(-) > > Index: linux-2.6/mm/filemap.c > =================================================================== > --- linux-2.6.orig/mm/filemap.c 2010-12-15 16:39:55.000000000 +0100 > +++ linux-2.6/mm/filemap.c 2010-12-15 16:41:24.000000000 +0100 > @@ -389,6 +389,47 @@ int filemap_write_and_wait_range(struct > } > EXPORT_SYMBOL(filemap_write_and_wait_range); > This function is exported. Please, add function description > +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 = mem_cgroup_cache_charge(new, current->mm, > + gfp_mask & GFP_RECLAIM_MASK); > + if (error) > + goto out; > + > + error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); > + if (error == 0) { > + 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_uncharge_cache_page(old); > + page_cache_release(old); Why do you release reference of old? > + } else > + mem_cgroup_uncharge_cache_page(new); > +out: > + 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 > Index: linux-2.6/include/linux/pagemap.h > =================================================================== > --- linux-2.6.orig/include/linux/pagemap.h 2010-12-15 16:39:39.000000000 +0100 > +++ linux-2.6/include/linux/pagemap.h 2010-12-15 16:41:24.000000000 +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 2010-12-15 16:39:39.000000000 +0100 > +++ linux-2.6/fs/fuse/dev.c 2010-12-15 16:41:24.000000000 +0100 > @@ -729,14 +729,12 @@ 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)) > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxxx For more info on Linux MM, > see: http://www.linux-mm.org/ . > Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ > Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a> > -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html