}
#endif
+static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
+static int shmem_replace_page(struct page **pagep, gfp_t gfp,
+ struct shmem_inode_info *info, pgoff_t index);
static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
* 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)
+ swp_entry_t swap, struct page **pagep)
{
struct address_space *mapping = info->vfs_inode.i_mapping;
void *radswap;
pgoff_t index;
- int error;
+ gfp_t gfp;
+ int error = 0;
radswap = swp_to_radix_entry(swap);
index = radix_tree_locate_item(&mapping->page_tree, radswap);
if (shmem_swaplist.next != &info->swaplist)
list_move_tail(&shmem_swaplist, &info->swaplist);
+ gfp = mapping_gfp_mask(mapping);
+ if (shmem_should_replace_page(*pagep, gfp)) {
+ mutex_unlock(&shmem_swaplist_mutex);
+ error = shmem_replace_page(pagep, gfp, info, index);
+ mutex_lock(&shmem_swaplist_mutex);
+ /*
+ * We needed to drop mutex to make that restrictive page
+ * allocation; but the inode might already be freed by now,
+ * and we cannot refer to inode or mapping or info to check.
+ * However, we do hold page lock on the PageSwapCache page,
+ * so can check if that still has our reference remaining.
+ */
+ if (!page_swapcount(*pagep))
+ error = -ENOENT;
+ }
+
/*
* We rely on shmem_swaplist_mutex, not only to protect the swaplist,
* 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 = shmem_add_to_page_cache(page, mapping, index,
+ if (!error)
+ error = shmem_add_to_page_cache(*pagep, 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);
+ delete_from_swap_cache(*pagep);
+ set_page_dirty(*pagep);
if (!error) {
spin_lock(&info->lock);
info->swapped--;
struct list_head *this, *next;
struct shmem_inode_info *info;
int found = 0;
- int error;
+ int error = 0;
+
+ /*
+ * There's a faint possibility that swap page was replaced before
+ * caller locked it: it will come back later with the right page.
+ */
+ if (unlikely(!PageSwapCache(page)))
+ goto out;
/*
* Charge page using GFP_KERNEL while we can wait, before taking
list_for_each_safe(this, next, &shmem_swaplist) {
info = list_entry(this, struct shmem_inode_info, swaplist);
if (info->swapped)
- found = shmem_unuse_inode(info, swap, page);
+ found = shmem_unuse_inode(info, swap, &page);
else
list_del_init(&info->swaplist);
cond_resched();
}
mutex_unlock(&shmem_swaplist_mutex);
- if (!found)
- mem_cgroup_uncharge_cache_page(page);
if (found < 0)
error = found;
out:
}
#endif
+/*
+ * When a page is moved from swapcache to shmem filecache (either by the
+ * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
+ * shmem_unuse_inode()), it may have been read in earlier from swap, in
+ * ignorance of the mapping it belongs to. If that mapping has special
+ * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
+ * we may need to copy to a suitable page before moving to filecache.
+ *
+ * In a future release, this may well be extended to respect cpuset and
+ * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
+ * but for now it is a simple matter of zone.
+ */
+static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
+{
+ return page_zonenum(page) > gfp_zone(gfp);
+}
+
+static int shmem_replace_page(struct page **pagep, gfp_t gfp,
+ struct shmem_inode_info *info, pgoff_t index)
+{
+ struct page *oldpage, *newpage;
+ struct address_space *swap_mapping;
+ pgoff_t swap_index;
+ int error;
+
+ oldpage = *pagep;
+ swap_index = page_private(oldpage);
+ swap_mapping = page_mapping(oldpage);
+
+ /*
+ * We have arrived here because our zones are constrained, so don't
+ * limit chance of success by further cpuset and node constraints.
+ */
+ gfp &= ~GFP_CONSTRAINT_MASK;
+ newpage = shmem_alloc_page(gfp, info, index);
+ if (!newpage)
+ return -ENOMEM;
+ VM_BUG_ON(shmem_should_replace_page(newpage, gfp));
+
+ *pagep = newpage;
+ page_cache_get(newpage);
+ copy_highpage(newpage, oldpage);
+
+ VM_BUG_ON(!PageLocked(oldpage));
+ __set_page_locked(newpage);
+ VM_BUG_ON(!PageUptodate(oldpage));
+ SetPageUptodate(newpage);
+ VM_BUG_ON(!PageSwapBacked(oldpage));
+ SetPageSwapBacked(newpage);
+ VM_BUG_ON(!swap_index);
+ set_page_private(newpage, swap_index);
+ VM_BUG_ON(!PageSwapCache(oldpage));
+ SetPageSwapCache(newpage);
+
+ /*
+ * Our caller will very soon move newpage out of swapcache, but it's
+ * a nice clean interface for us to replace oldpage by newpage there.
+ */
+ spin_lock_irq(&swap_mapping->tree_lock);
+ error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
+ newpage);
+ __inc_zone_page_state(newpage, NR_FILE_PAGES);
+ __dec_zone_page_state(oldpage, NR_FILE_PAGES);
+ spin_unlock_irq(&swap_mapping->tree_lock);
+ BUG_ON(error);
+
+ mem_cgroup_replace_page_cache(oldpage, newpage);
+ lru_cache_add_anon(newpage);
+
+ ClearPageSwapCache(oldpage);
+ set_page_private(oldpage, 0);
+
+ unlock_page(oldpage);
+ page_cache_release(oldpage);
+ page_cache_release(oldpage);
+ return 0;
+}
+
/*
* shmem_getpage_gfp - find page in cache, or get from swap, or allocate
*
/* We have to do this with page locked to prevent races */
lock_page(page);
+ if (!PageSwapCache(page) || page->mapping) {
+ error = -EEXIST; /* try again */
+ goto failed;
+ }
if (!PageUptodate(page)) {
error = -EIO;
goto failed;
}
wait_on_page_writeback(page);
- /* Someone may have already done it for us */
- if (page->mapping) {
- if (page->mapping == mapping &&
- page->index == index)
- goto done;
- error = -EEXIST;
- goto failed;
+ if (shmem_should_replace_page(page, gfp)) {
+ error = shmem_replace_page(&page, gfp, info, index);
+ if (error)
+ goto failed;
}
error = mem_cgroup_cache_charge(page, current->mm,
if (sgp == SGP_DIRTY)
set_page_dirty(page);
}
-done:
+
/* Perhaps the file has been truncated since we checked */
if (sgp != SGP_WRITE &&
((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
projects / ~andy / linux / commitdiff