btrfs: start readahead also in seed devices

Currently, btrfs does not consult seed devices to start readahead. As a
result, if readahead zone is added to the seed devices, btrfs_reada_wait()
indefinitely wait for the reada_ctl to finish.

You can reproduce the hung by modifying btrfs/163 to have larger initial
file size (e.g. xfs_io pwrite 4M instead of current 256K).

Fixes: 7414a03fbf9e ("btrfs: initial readahead code and prototypes")
Cc: stable@vger.kernel.org # 3.2+: ce7791ffee1e: Btrfs: fix race between readahead and device replace/removal
Cc: stable@vger.kernel.org # 3.2+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index 10d9589001a9..bb5bd49573b4 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -747,6 +747,7 @@ static void __reada_start_machine(struct btrfs_fs_info *fs_info)
         u64 total = 0;
         int i;
 
+again:
         do {
                 enqueued = 0;
                 mutex_lock(&fs_devices->device_list_mutex);
@@ -758,6 +759,10 @@ static void __reada_start_machine(struct btrfs_fs_info *fs_info)
                 mutex_unlock(&fs_devices->device_list_mutex);
                 total += enqueued;
         } while (enqueued && total < 10000);
+        if (fs_devices->seed) {
+                fs_devices = fs_devices->seed;
+                goto again;
+        }
 
         if (enqueued == 0)
                 return;