Btrfs: checksum file data at bio submission time instead of during writepage

When we checkum file data during writepage, the checksumming is done one
page at a time, making it difficult to do bulk metadata modifications
to insert checksums for large ranges of the file at once.

This patch changes btrfs to checksum on a per-bio basis instead.  The
bios are checksummed before they are handed off to the block layer, so
each bio is contiguous and only has pages from the same inode.

Checksumming on a bio basis allows us to insert and modify the file
checksum items in large groups.  It also allows the checksumming to
be done more easily by async worker threads.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 30 insertions, 2 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3e79572a5cb1..bbb71fad861a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -16,6 +16,7 @@
  * Boston, MA 021110-1307, USA.
  */
 
+#include <linux/bio.h>
 #include <linux/buffer_head.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
@@ -294,6 +295,32 @@ int btrfs_clear_bit_hook(struct inode *inode, u64 start, u64 end,
         return 0;
 }
 
+int btrfs_submit_bio_hook(int rw, struct bio *bio)
+{
+        // struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+        struct bio_vec *bvec = bio->bi_io_vec;
+        struct inode *inode = bvec->bv_page->mapping->host;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct btrfs_trans_handle *trans;
+        int ret = 0;
+
+        if (rw != WRITE)
+                return 0;
+
+        if (btrfs_test_opt(root, NODATASUM) ||
+            btrfs_test_flag(inode, NODATASUM))
+                return 0;
+
+        mutex_lock(&root->fs_info->fs_mutex);
+        trans = btrfs_start_transaction(root, 1);
+        btrfs_set_trans_block_group(trans, inode);
+        btrfs_csum_file_blocks(trans, root, inode, bio);
+        ret = btrfs_end_transaction(trans, root);
+        BUG_ON(ret);
+        mutex_unlock(&root->fs_info->fs_mutex);
+        return ret;
+}
+#if 0
 int btrfs_writepage_io_hook(struct page *page, u64 start, u64 end)
 {
         struct inode *inode = page->mapping->host;
@@ -318,7 +345,7 @@ int btrfs_writepage_io_hook(struct page *page, u64 start, u64 end)
         mutex_unlock(&root->fs_info->fs_mutex);
         return ret;
 }
-
+#endif
 int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)
 {
         int ret = 0;
@@ -3022,7 +3049,8 @@ static struct file_operations btrfs_dir_file_operations = {
 
 static struct extent_io_ops btrfs_extent_io_ops = {
         .fill_delalloc = run_delalloc_range,
-        .writepage_io_hook = btrfs_writepage_io_hook,
+        // .writepage_io_hook = btrfs_writepage_io_hook,
+        .submit_bio_hook = btrfs_submit_bio_hook,
         .readpage_io_hook = btrfs_readpage_io_hook,
         .readpage_end_io_hook = btrfs_readpage_end_io_hook,
         .set_bit_hook = btrfs_set_bit_hook,