Btrfs: always store the mirror we read the eb from

A user reported a panic where we were trying to fix a bad mirror but the
mirror number we were giving was 0, which is invalid.  This is because we
don't do the transid verification until after the read, so as far as the
read code is concerned the read was a success.  So instead store the mirror
we read from so that if there is some failure post read we know which mirror
to try next and which mirror needs to be fixed if we find a good copy of the
block.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 8 insertions, 8 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b9866f27ebd7..d0c969beaad4 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -383,17 +383,16 @@ static int btree_read_extent_buffer_pages(struct btrfs_root *root,
                 if (test_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags))
                         break;
 
-                if (!failed_mirror) {
-                        failed = 1;
-                        printk(KERN_ERR "failed mirror was %d\n", eb->failed_mirror);
-                        failed_mirror = eb->failed_mirror;
-                }
-
                 num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
                                               eb->start, eb->len);
                 if (num_copies == 1)
                         break;
 
+                if (!failed_mirror) {
+                        failed = 1;
+                        failed_mirror = eb->read_mirror;
+                }
+
                 mirror_num++;
                 if (mirror_num == failed_mirror)
                         mirror_num++;
@@ -564,7 +563,7 @@ struct extent_buffer *find_eb_for_page(struct extent_io_tree *tree,
 }
 
 static int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
-                               struct extent_state *state)
+                               struct extent_state *state, int mirror)
 {
         struct extent_io_tree *tree;
         u64 found_start;
@@ -589,6 +588,7 @@ static int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
         if (!reads_done)
                 goto err;
 
+        eb->read_mirror = mirror;
         if (test_bit(EXTENT_BUFFER_IOERR, &eb->bflags)) {
                 ret = -EIO;
                 goto err;
@@ -652,7 +652,7 @@ static int btree_io_failed_hook(struct page *page, int failed_mirror)
 
         eb = (struct extent_buffer *)page->private;
         set_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
-        eb->failed_mirror = failed_mirror;
+        eb->read_mirror = failed_mirror;
         if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
                 btree_readahead_hook(root, eb, eb->start, -EIO);
         return -EIO;    /* we fixed nothing */