Btrfs: Add O_DIRECT read and write (writes == buffered + cache flush)

[karo-tx-linux.git] / fs / btrfs / inode.c

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 48f1d1b96450c2725956d7dae33168dddd83ea53..32e778fb014ef3c68ee32e8e754532bf591d8641 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2265,6 +2265,70 @@ out:
        return em;
 }
 
+static int btrfs_get_block(struct inode *inode, sector_t iblock,
+                       struct buffer_head *bh_result, int create)
+{
+       struct extent_map *em;
+       u64 start = (u64)iblock << inode->i_blkbits;
+       struct btrfs_multi_bio *multi = NULL;
+       struct btrfs_root *root = BTRFS_I(inode)->root;
+       u64 len;
+       u64 logical;
+       u64 map_length;
+       int ret = 0;
+
+       em = btrfs_get_extent(inode, NULL, 0, start, bh_result->b_size, 0);
+
+       if (!em || IS_ERR(em))
+               goto out;
+
+       if (em->start > start || em->start + em->len <= start)
+           goto out;
+
+       if (em->block_start == EXTENT_MAP_INLINE) {
+               ret = -EINVAL;
+               goto out;
+       }
+
+       if (em->block_start == EXTENT_MAP_HOLE ||
+           em->block_start == EXTENT_MAP_DELALLOC) {
+               goto out;
+       }
+
+       len = em->start + em->len - start;
+       len = min_t(u64, len, INT_LIMIT(typeof(bh_result->b_size)));
+
+       logical = start - em->start;
+       logical = em->block_start + logical;
+
+       map_length = len;
+       ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
+                             logical, &map_length, &multi, 0);
+       BUG_ON(ret);
+       bh_result->b_blocknr = multi->stripes[0].physical >> inode->i_blkbits;
+       bh_result->b_size = min(map_length, len);
+       bh_result->b_bdev = multi->stripes[0].dev->bdev;
+       set_buffer_mapped(bh_result);
+       kfree(multi);
+out:
+       free_extent_map(em);
+       return ret;
+}
+
+static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
+                       const struct iovec *iov, loff_t offset,
+                       unsigned long nr_segs)
+{
+       struct file *file = iocb->ki_filp;
+       struct inode *inode = file->f_mapping->host;
+
+       if (rw == WRITE)
+               return -EINVAL;
+
+       return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
+                                 offset, nr_segs, btrfs_get_block, NULL);
+}
+
 static sector_t btrfs_bmap(struct address_space *mapping, sector_t iblock)
 {
        return extent_bmap(mapping, iblock, btrfs_get_extent);
@@ -3136,6 +3200,7 @@ out_fail:
        btrfs_throttle(root);
        return err;
 }
+
 static int btrfs_permission(struct inode *inode, int mask,
                            struct nameidata *nd)
 {
@@ -3193,6 +3258,7 @@ static struct address_space_operations btrfs_aops = {
        .readpages      = btrfs_readpages,
        .sync_page      = block_sync_page,
        .bmap           = btrfs_bmap,
+       .direct_IO      = btrfs_direct_IO,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
        .set_page_dirty = __set_page_dirty_nobuffers,