diff options
| -rw-r--r-- | mm/shmem.c | 133 |
1 files changed, 107 insertions, 26 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 4439b7d55819..174f97188e8a 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -262,6 +262,55 @@ static int shmem_radix_tree_replace(struct address_space *mapping, } /* + * Like add_to_page_cache_locked, but error if expected item has gone. + */ +static int shmem_add_to_page_cache(struct page *page, + struct address_space *mapping, + pgoff_t index, gfp_t gfp, void *expected) +{ + int error; + + VM_BUG_ON(!PageLocked(page)); + VM_BUG_ON(!PageSwapBacked(page)); + + error = mem_cgroup_cache_charge(page, current->mm, + gfp & GFP_RECLAIM_MASK); + if (error) + goto out; + if (!expected) + error = radix_tree_preload(gfp & GFP_RECLAIM_MASK); + if (!error) { + page_cache_get(page); + page->mapping = mapping; + page->index = index; + + spin_lock_irq(&mapping->tree_lock); + if (!expected) + error = radix_tree_insert(&mapping->page_tree, + index, page); + else + error = shmem_radix_tree_replace(mapping, index, + expected, page); + if (!error) { + mapping->nrpages++; + __inc_zone_page_state(page, NR_FILE_PAGES); + __inc_zone_page_state(page, NR_SHMEM); + spin_unlock_irq(&mapping->tree_lock); + } else { + page->mapping = NULL; + spin_unlock_irq(&mapping->tree_lock); + page_cache_release(page); + } + if (!expected) + radix_tree_preload_end(); + } + if (error) + mem_cgroup_uncharge_cache_page(page); +out: + return error; +} + +/* * Like find_get_pages, but collecting swap entries as well as pages. */ static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping, @@ -309,6 +358,42 @@ export: } /* + * Lockless lookup of swap entry in radix tree, avoiding refcount on pages. + */ +static pgoff_t shmem_find_swap(struct address_space *mapping, void *radswap) +{ + void **slots[PAGEVEC_SIZE]; + pgoff_t indices[PAGEVEC_SIZE]; + unsigned int nr_found; + +restart: + nr_found = 1; + indices[0] = -1; + while (nr_found) { + pgoff_t index = indices[nr_found - 1] + 1; + unsigned int i; + + rcu_read_lock(); + nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, + slots, indices, index, PAGEVEC_SIZE); + for (i = 0; i < nr_found; i++) { + void *item = radix_tree_deref_slot(slots[i]); + if (radix_tree_deref_retry(item)) { + rcu_read_unlock(); + goto restart; + } + if (item == radswap) { + rcu_read_unlock(); + return indices[i]; + } + } + rcu_read_unlock(); + cond_resched(); + } + return -1; +} + +/* * Remove swap entry from radix tree, free the swap and its page cache. */ static int shmem_free_swap(struct address_space *mapping, @@ -515,23 +600,21 @@ static void shmem_evict_inode(struct inode *inode) end_writeback(inode); } +/* + * If swap found in inode, free it and move page from swapcache to filecache. + */ static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t swap, struct page *page) { struct address_space *mapping = info->vfs_inode.i_mapping; + void *radswap; pgoff_t index; int error; - for (index = 0; index < SHMEM_NR_DIRECT; index++) - if (shmem_get_swap(info, index).val == swap.val) - goto found; - return 0; -found: - spin_lock(&info->lock); - if (shmem_get_swap(info, index).val != swap.val) { - spin_unlock(&info->lock); + radswap = swp_to_radix_entry(swap); + index = shmem_find_swap(mapping, radswap); + if (index == -1) return 0; - } /* * Move _head_ to start search for next from here. @@ -547,23 +630,30 @@ found: * but also to hold up shmem_evict_inode(): so inode cannot be freed * beneath us (pagelock doesn't help until the page is in pagecache). */ - error = add_to_page_cache_locked(page, mapping, index, GFP_NOWAIT); + error = shmem_add_to_page_cache(page, mapping, index, + GFP_NOWAIT, radswap); /* which does mem_cgroup_uncharge_cache_page on error */ if (error != -ENOMEM) { + /* + * Truncation and eviction use free_swap_and_cache(), which + * only does trylock page: if we raced, best clean up here. + */ delete_from_swap_cache(page); set_page_dirty(page); - shmem_put_swap(info, index, (swp_entry_t){0}); - info->swapped--; - swap_free(swap); + if (!error) { + spin_lock(&info->lock); + info->swapped--; + spin_unlock(&info->lock); + swap_free(swap); + } error = 1; /* not an error, but entry was found */ } - spin_unlock(&info->lock); return error; } /* - * shmem_unuse() search for an eventually swapped out shmem page. + * Search through swapped inodes to find and replace swap by page. */ int shmem_unuse(swp_entry_t swap, struct page *page) { @@ -576,20 +666,12 @@ int shmem_unuse(swp_entry_t swap, struct page *page) * Charge page using GFP_KERNEL while we can wait, before taking * the shmem_swaplist_mutex which might hold up shmem_writepage(). * Charged back to the user (not to caller) when swap account is used. - * add_to_page_cache() will be called with GFP_NOWAIT. + * shmem_add_to_page_cache() will be called with GFP_NOWAIT. */ error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL); if (error) goto out; - /* - * Try to preload while we can wait, to not make a habit of - * draining atomic reserves; but don't latch on to this cpu, - * it's okay if sometimes we get rescheduled after this. - */ - error = radix_tree_preload(GFP_KERNEL); - if (error) - goto uncharge; - radix_tree_preload_end(); + /* No radix_tree_preload: swap entry keeps a place for page in tree */ mutex_lock(&shmem_swaplist_mutex); list_for_each_safe(this, next, &shmem_swaplist) { @@ -608,7 +690,6 @@ int shmem_unuse(swp_entry_t swap, struct page *page) } mutex_unlock(&shmem_swaplist_mutex); -uncharge: if (!found) mem_cgroup_uncharge_cache_page(page); if (found < 0) |