2 files changed, 56 insertions, 7 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 70af24aa582b..51aba8cee7ce 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -134,6 +134,7 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
         return ret;
 }
 
+#if 0 /* broken */
 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
                           struct bio *bio)
 {
@@ -200,7 +201,7 @@ int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
                 diff = diff * BTRFS_CRC32_SIZE;
 
                 read_extent_buffer(path->nodes[0], &sum,
-                                   (unsigned long)item + diff,
+                                   ((unsigned long)item) + diff,
                                    BTRFS_CRC32_SIZE);
 found:
                 set_state_private(io_tree, offset, sum);
@@ -210,6 +211,7 @@ found:
         btrfs_free_path(path);
         return 0;
 }
+#endif
 
 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
                        struct bio *bio)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8a405a5fa6a3..99121a55ffbe 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -382,12 +382,6 @@ int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
         BUG_ON(ret);
 
         if (!(rw & (1 << BIO_RW))) {
-                if (!btrfs_test_opt(root, NODATASUM) &&
-                    !btrfs_test_flag(inode, NODATASUM)) {
-                        mutex_lock(&BTRFS_I(inode)->csum_mutex);
-                        btrfs_lookup_bio_sums(root, inode, bio);
-                        mutex_unlock(&BTRFS_I(inode)->csum_mutex);
-                }
                 goto mapit;
         }
 
@@ -595,6 +589,58 @@ int btrfs_writepage_end_io_hook(struct page *page, u64 start, u64 end,
         return btrfs_finish_ordered_io(page->mapping->host, start, end);
 }
 
+int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)
+{
+        int ret = 0;
+        struct inode *inode = page->mapping->host;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+        struct btrfs_csum_item *item;
+        struct btrfs_path *path = NULL;
+        u32 csum;
+
+        if (btrfs_test_opt(root, NODATASUM) ||
+            btrfs_test_flag(inode, NODATASUM))
+                return 0;
+
+        /*
+         * It is possible there is an ordered extent that has
+         * not yet finished for this range in the file.  If so,
+         * that extent will have a csum cached, and it will insert
+         * the sum after all the blocks in the extent are fully
+         * on disk.  So, look for an ordered extent and use the
+         * sum if found.  We have to do this before looking in the
+         * btree because csum items are pre-inserted based on
+         * the file size.  btrfs_lookup_csum might find an item
+         * that still hasn't been fully filled.
+         */
+        ret = btrfs_find_ordered_sum(inode, start, &csum);
+        if (ret == 0)
+                goto found;
+
+        ret = 0;
+        path = btrfs_alloc_path();
+        item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, start, 0);
+        if (IS_ERR(item)) {
+                ret = PTR_ERR(item);
+                /* a csum that isn't present is a preallocated region. */
+                if (ret == -ENOENT || ret == -EFBIG)
+                        ret = 0;
+                csum = 0;
+                printk("no csum found for inode %lu start %Lu\n", inode->i_ino,
+                       start);
+                goto out;
+        }
+        read_extent_buffer(path->nodes[0], &csum, (unsigned long)item,
+                           BTRFS_CRC32_SIZE);
+found:
+        set_state_private(io_tree, start, csum);
+out:
+        if (path)
+                btrfs_free_path(path);
+        return ret;
+}
+
 struct io_failure_record {
         struct page *page;
         u64 start;
@@ -3580,6 +3626,7 @@ static struct extent_io_ops btrfs_extent_io_ops = {
         .fill_delalloc = run_delalloc_range,
         .submit_bio_hook = btrfs_submit_bio_hook,
         .merge_bio_hook = btrfs_merge_bio_hook,
+        .readpage_io_hook = btrfs_readpage_io_hook,
         .readpage_end_io_hook = btrfs_readpage_end_io_hook,
         .writepage_end_io_hook = btrfs_writepage_end_io_hook,
         .writepage_start_hook = btrfs_writepage_start_hook,