On 02/27/2018 05:12 PM, Qu Wenruo wrote:
Original --check-data-csum option will skip the extra copy if the first
copy matches csum.

Since offline scrub (with recoverability report) is still out-of-tree, at
least enhance --check-data-csum option to handle multiple copies.

Signed-off-by: Qu Wenruo <w...@suse.com>
---
  check/main.c | 65 ++++++++++++++++++++++++++++++------------------------------
  1 file changed, 32 insertions(+), 33 deletions(-)

diff --git a/check/main.c b/check/main.c
index 97baae583f04..f25fdc765d63 100644
--- a/check/main.c
+++ b/check/main.c
@@ -5381,42 +5381,37 @@ static int check_extent_csums(struct btrfs_root *root, 
u64 bytenr,
        if (!data)
                return -ENOMEM;
+ num_copies = btrfs_num_copies(root->fs_info, bytenr, num_bytes);
        while (offset < num_bytes) {
-               mirror = 0;
-again:
-               read_len = num_bytes - offset;
-               /* read as much space once a time */
-               ret = read_extent_data(fs_info, data + offset,
-                               bytenr + offset, &read_len, mirror);
-               if (ret)
-                       goto out;
-               data_checked = 0;
-               /* verify every 4k data's checksum */
-               while (data_checked < read_len) {
-                       csum = ~(u32)0;
-                       tmp = offset + data_checked;
-
-                       csum = btrfs_csum_data((char *)data + tmp,
-                                              csum, fs_info->sectorsize);
-                       btrfs_csum_final(csum, (u8 *)&csum);
-
-                       csum_offset = leaf_offset +
-                                tmp / fs_info->sectorsize * csum_size;
-                       read_extent_buffer(eb, (char *)&csum_expected,
-                                          csum_offset, csum_size);
-                       /* try another mirror */
-                       if (csum != csum_expected) {
-                               fprintf(stderr, "mirror %d bytenr %llu csum %u 
expected csum %u\n",
+               for (mirror = 1; mirror <= num_copies; mirror++) {

Got your point.
But what confuses me is that why mirror starts from 1 here.
The mirror influences btrfs_map_block() which is not related
to this patch though.

Thanks,
Su
+                       read_len = num_bytes - offset;
+                       /* read as much space once a time */
+                       ret = read_extent_data(fs_info, data + offset,
+                                       bytenr + offset, &read_len, mirror);
+                       if (ret)
+                               goto out;
+
+                       data_checked = 0;
+                       /* verify every 4k data's checksum */
+                       while (data_checked < read_len) {
+                               csum = ~(u32)0;
+                               tmp = offset + data_checked;
+
+                               csum = btrfs_csum_data((char *)data + tmp,
+                                               csum, fs_info->sectorsize);
+                               btrfs_csum_final(csum, (u8 *)&csum);
+
+                               csum_offset = leaf_offset +
+                                        tmp / fs_info->sectorsize * csum_size;
+                               read_extent_buffer(eb, (char *)&csum_expected,
+                                                  csum_offset, csum_size);
+                               if (csum != csum_expected)
+                                       fprintf(stderr,
+                       "mirror %d bytenr %llu csum %u expected csum %u\n",
                                                mirror, bytenr + tmp,
                                                csum, csum_expected);
-                               num_copies = btrfs_num_copies(root->fs_info,
-                                               bytenr, num_bytes);
-                               if (mirror < num_copies - 1) {
-                                       mirror += 1;
-                                       goto again;
-                               }
+                               data_checked += fs_info->sectorsize;
                        }
-                       data_checked += fs_info->sectorsize;
                }
                offset += read_len;
        }
@@ -5624,7 +5619,11 @@ static int check_csums(struct btrfs_root *root)
                leaf_offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
                ret = check_extent_csums(root, key.offset, data_len,
                                         leaf_offset, leaf);
-               if (ret)
+               /*
+                * Only break for fatal errors, if mismatch is found,
+                * continue checking until all extents are checked.
+                */
+               if (ret < 0)
                        break;
  skip_csum_check:
                if (!num_bytes) {



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