Btrfs: fix kernel oops while reading compressed data

The kernel oops happens at

kernel BUG at fs/btrfs/extent_io.c:2104!
...
RIP: clean_io_failure+0x263/0x2a0 [btrfs]

It's showing that read-repair code is using an improper mirror index.
This is due to the fact that compression read's endio hasn't recorded
the failed mirror index in %cb->orig_bio.

With this, btrfs's read-repair can work properly on reading compressed
data.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reported-by: Paul Jones <paul@pauljones.id.au>
Tested-by: Paul Jones <paul@pauljones.id.au>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 883ecc58fd0dabeda45dd05557c503bd47a71902..c6aa53c4c1020180ef609fe1068d442e194bdd0f 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -107,6 +107,7 @@ static void end_compressed_bio_read(struct bio *bio)
        struct inode *inode;
        struct page *page;
        unsigned long index;
+       unsigned int mirror = btrfs_io_bio(bio)->mirror_num;
        int ret;
 
        if (bio->bi_status)
@@ -118,6 +119,14 @@ static void end_compressed_bio_read(struct bio *bio)
        if (!refcount_dec_and_test(&cb->pending_bios))
                goto out;
 
+       /*
+        * Record the correct mirror_num in cb->orig_bio so that
+        * read-repair can work properly.
+        */
+       ASSERT(btrfs_io_bio(cb->orig_bio));
+       btrfs_io_bio(cb->orig_bio)->mirror_num = mirror;
+       cb->mirror_num = mirror;
+
        inode = cb->inode;
        ret = check_compressed_csum(BTRFS_I(inode), cb,
                                    (u64)bio->bi_iter.bi_sector << 9);