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-rw-r--r--mm/shmem.c69
1 files changed, 44 insertions, 25 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index e577adf4ae8..4ae47f54c82 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -827,6 +827,7 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, s
struct page *subdir;
swp_entry_t *ptr;
int offset;
+ int error;
idx = 0;
ptr = info->i_direct;
@@ -884,7 +885,20 @@ lost2:
found:
idx += offset;
inode = &info->vfs_inode;
- if (add_to_page_cache(page, inode->i_mapping, idx, GFP_ATOMIC) == 0) {
+ error = add_to_page_cache(page, inode->i_mapping, idx, GFP_ATOMIC);
+ if (error == -EEXIST) {
+ struct page *filepage = find_get_page(inode->i_mapping, idx);
+ if (filepage) {
+ /*
+ * There might be a more uptodate page coming down
+ * from a stacked writepage: forget our swappage if so.
+ */
+ if (PageUptodate(filepage))
+ error = 0;
+ page_cache_release(filepage);
+ }
+ }
+ if (!error) {
delete_from_swap_cache(page);
set_page_dirty(page);
info->flags |= SHMEM_PAGEIN;
@@ -937,44 +951,45 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
struct inode *inode;
BUG_ON(!PageLocked(page));
- /*
- * shmem_backing_dev_info's capabilities prevent regular writeback or
- * sync from ever calling shmem_writepage; but a stacking filesystem
- * may use the ->writepage of its underlying filesystem, in which case
- * we want to do nothing when that underlying filesystem is tmpfs
- * (writing out to swap is useful as a response to memory pressure, but
- * of no use to stabilize the data) - just redirty the page, unlock it
- * and claim success in this case. AOP_WRITEPAGE_ACTIVATE, and the
- * page_mapped check below, must be avoided unless we're in reclaim.
- */
- if (!wbc->for_reclaim) {
- set_page_dirty(page);
- unlock_page(page);
- return 0;
- }
- BUG_ON(page_mapped(page));
-
mapping = page->mapping;
index = page->index;
inode = mapping->host;
info = SHMEM_I(inode);
if (info->flags & VM_LOCKED)
goto redirty;
- swap = get_swap_page();
- if (!swap.val)
+ if (!total_swap_pages)
goto redirty;
+ /*
+ * shmem_backing_dev_info's capabilities prevent regular writeback or
+ * sync from ever calling shmem_writepage; but a stacking filesystem
+ * may use the ->writepage of its underlying filesystem, in which case
+ * tmpfs should write out to swap only in response to memory pressure,
+ * and not for pdflush or sync. However, in those cases, we do still
+ * want to check if there's a redundant swappage to be discarded.
+ */
+ if (wbc->for_reclaim)
+ swap = get_swap_page();
+ else
+ swap.val = 0;
+
spin_lock(&info->lock);
- shmem_recalc_inode(inode);
if (index >= info->next_index) {
BUG_ON(!(info->flags & SHMEM_TRUNCATE));
goto unlock;
}
entry = shmem_swp_entry(info, index, NULL);
- BUG_ON(!entry);
- BUG_ON(entry->val);
+ if (entry->val) {
+ /*
+ * The more uptodate page coming down from a stacked
+ * writepage should replace our old swappage.
+ */
+ free_swap_and_cache(*entry);
+ shmem_swp_set(info, entry, 0);
+ }
+ shmem_recalc_inode(inode);
- if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
+ if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
remove_from_page_cache(page);
shmem_swp_set(info, entry, swap.val);
shmem_swp_unmap(entry);
@@ -986,6 +1001,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
spin_unlock(&shmem_swaplist_lock);
}
swap_duplicate(swap);
+ BUG_ON(page_mapped(page));
page_cache_release(page); /* pagecache ref */
set_page_dirty(page);
unlock_page(page);
@@ -998,7 +1014,10 @@ unlock:
swap_free(swap);
redirty:
set_page_dirty(page);
- return AOP_WRITEPAGE_ACTIVATE; /* Return with the page locked */
+ if (wbc->for_reclaim)
+ return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */
+ unlock_page(page);
+ return 0;
}
#ifdef CONFIG_NUMA