[PATCH U-BOOT 2/3] btrfs: btrfs_file_read: allow opportunistic read until the end

[Dominique Martinet]

From: Dominique Martinet <dominique.martinet at atmark-techno.com>

btrfs_file_read main 'aligned read' loop would limit the last read to
the aligned end even if the data is present in the extent: there is no
reason not to read the data that we know will be presented correctly.

If that somehow fails cur only advances up to the aligned_end anyway and
the file tail is read through the old code unchanged; this could be
required if e.g. the end data is inlined.

Signed-off-by: Dominique Martinet <dominique.martinet at atmark-techno.com>
---
 fs/btrfs/inode.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3d6e39e6544d..efffec0f2e68 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -663,7 +663,8 @@ int btrfs_file_read(struct btrfs_root *root, u64 ino, u64 file_offset, u64 len,
 	struct btrfs_path path;
 	struct btrfs_key key;
 	u64 aligned_start = round_down(file_offset, fs_info->sectorsize);
-	u64 aligned_end = round_down(file_offset + len, fs_info->sectorsize);
+	u64 end = file_offset + len;
+	u64 aligned_end = round_down(end, fs_info->sectorsize);
 	u64 next_offset;
 	u64 cur = aligned_start;
 	int ret = 0;
@@ -743,26 +744,26 @@ int btrfs_file_read(struct btrfs_root *root, u64 ino, u64 file_offset, u64 len,
 		extent_num_bytes = btrfs_file_extent_num_bytes(path.nodes[0],
 							       fi);
 		ret = btrfs_read_extent_reg(&path, fi, cur,
-				min(extent_num_bytes, aligned_end - cur),
+				min(extent_num_bytes, end - cur),
 				dest + cur - file_offset);
 		if (ret < 0)
 			goto out;
-		cur += min(extent_num_bytes, aligned_end - cur);
+		cur += min(extent_num_bytes, end - cur);
 	}
 
 	/* Read the tailing unaligned part*/
-	if (file_offset + len != aligned_end) {
+	if (file_offset + len != cur) {
 		btrfs_release_path(&path);
-		ret = lookup_data_extent(root, &path, ino, aligned_end,
+		ret = lookup_data_extent(root, &path, ino, cur,
 					 &next_offset);
 		/* <0 is error, >0 means no extent */
 		if (ret)
 			goto out;
 		fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
 				    struct btrfs_file_extent_item);
-		ret = read_and_truncate_page(&path, fi, aligned_end,
-				file_offset + len - aligned_end,
-				dest + aligned_end - file_offset);
+		ret = read_and_truncate_page(&path, fi, cur,
+				file_offset + len - cur,
+				dest + cur - file_offset);
 	}
 out:
 	btrfs_release_path(&path);

-- 
2.39.2