Btrfs-progs: map-logical: introduce write_extent_content function

This function will write extent content info desired file.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

diff --git a/btrfs-map-logical.c b/btrfs-map-logical.c
index 22ece82..1ee101c 100644 (file)
--- a/btrfs-map-logical.c
+++ b/btrfs-map-logical.c
@@ -30,6 +30,8 @@
 #include "list.h"
 #include "utils.h"
 
+#define BUFFER_SIZE (64 * 1024)
+
 /* we write the mirror info to stdout unless they are dumping the data
  * to stdout
  * */
@@ -156,6 +158,38 @@ static int print_mapping_info(struct btrfs_fs_info *fs_info, u64 logical,
        return ret;
 }
 
+/* Same requisition as print_mapping_info function */
+static int write_extent_content(struct btrfs_fs_info *fs_info, int out_fd,
+                               u64 logical, u64 length, int mirror)
+{
+       char buffer[BUFFER_SIZE];
+       u64 cur_offset = 0;
+       u64 cur_len;
+       int ret = 0;
+
+       while (cur_offset < length) {
+               cur_len = min_t(u64, length - cur_offset, BUFFER_SIZE);
+               ret = read_extent_data(fs_info->tree_root, buffer,
+                                      logical + cur_offset, &cur_len, mirror);
+               if (ret < 0) {
+                       fprintf(stderr,
+                               "Failed to read extent at [%llu, %llu]: %s\n",
+                               logical, logical + length, strerror(-ret));
+                       return ret;
+               }
+               ret = write(out_fd, buffer, cur_len);
+               if (ret < 0 || ret != cur_len) {
+                       if (ret > 0)
+                               ret = -EINTR;
+                       fprintf(stderr, "output file write failed: %s\n",
+                               strerror(-ret));
+                       return ret;
+               }
+               cur_offset += cur_len;
+       }
+       return ret;
+}
+
 static struct extent_buffer * debug_read_block(struct btrfs_root *root,
                u64 bytenr, u32 blocksize, u64 copy)
 {