[PATCH] splice: LRU fixups

Nick says that the current construct isn't safe. This goes back to the
original, but sets PIPE_BUF_FLAG_LRU on user pages as well as they all
seem to be on the LRU in the first place.

Signed-off-by: Jens Axboe <axboe@suse.de>

2 files changed, 14 insertions, 24 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 27f5e3738a7b..0b202425b0b5 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -78,6 +78,7 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
                 return 1;
         }
 
+        buf->flags |= PIPE_BUF_FLAG_LRU;
         return 0;
 }
 
@@ -85,6 +86,7 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
                                         struct pipe_buffer *buf)
 {
         page_cache_release(buf->page);
+        buf->flags &= ~PIPE_BUF_FLAG_LRU;
 }
 
 static int page_cache_pipe_buf_pin(struct pipe_inode_info *info,
@@ -141,6 +143,7 @@ static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
                 return 1;
 
+        buf->flags |= PIPE_BUF_FLAG_LRU;
         return generic_pipe_buf_steal(pipe, buf);
 }
 
@@ -566,37 +569,23 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
          */
         if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) {
                 /*
-                 * If steal succeeds, buf->page is now pruned from the vm
-                 * side (page cache) and we can reuse it. The page will also
-                 * be locked on successful return.
+                 * If steal succeeds, buf->page is now pruned from the
+                 * pagecache and we can reuse it. The page will also be
+                 * locked on successful return.
                  */
                 if (buf->ops->steal(info, buf))
                         goto find_page;
 
                 page = buf->page;
-                page_cache_get(page);
-
-                /*
-                 * page must be on the LRU for adding to the pagecache.
-                 * Check this without grabbing the zone lock, if it isn't
-                 * the do grab the zone lock, recheck, and add if necessary.
-                 */
-                if (!PageLRU(page)) {
-                        struct zone *zone = page_zone(page);
-
-                        spin_lock_irq(&zone->lru_lock);
-                        if (!PageLRU(page)) {
-                                SetPageLRU(page);
-                                add_page_to_inactive_list(zone, page);
-                        }
-                        spin_unlock_irq(&zone->lru_lock);
-                }
-
                 if (add_to_page_cache(page, mapping, index, gfp_mask)) {
-                        page_cache_release(page);
                         unlock_page(page);
                         goto find_page;
                 }
+
+                page_cache_get(page);
+
+                if (!(buf->flags & PIPE_BUF_FLAG_LRU))
+                        lru_cache_add(page);
         } else {
 find_page:
                 page = find_lock_page(mapping, index);
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index ba73108cbf8b..ea4f7cd7bfd8 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -5,8 +5,9 @@
 
 #define PIPE_BUFFERS (16)
 
-#define PIPE_BUF_FLAG_ATOMIC    0x01    /* was atomically mapped */
-#define PIPE_BUF_FLAG_GIFT      0x02    /* page is a gift */
+#define PIPE_BUF_FLAG_LRU       0x01    /* page is on the LRU */
+#define PIPE_BUF_FLAG_ATOMIC    0x02    /* was atomically mapped */
+#define PIPE_BUF_FLAG_GIFT      0x04    /* page is a gift */
 
 struct pipe_buffer {
         struct page *page;