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@xxxxxxxxxxxxxxx # 3.2+: ce7791ffee1e: Btrfs: fix race between readahead and device replace/removal
Cc: stable@xxxxxxxxxxxxxxx # 3.2+
Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
---
fs/btrfs/reada.c | 5 +++++
1 file changed, 5 insertions(+)
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;
--
2.21.0
