diff options
| -rw-r--r-- | mm/shmem.c | 69 |
1 files changed, 44 insertions, 25 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index e577adf4ae85..4ae47f54c822 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 |