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+ Signed-off-by: Naohiro Aota naohiro.aota@wdc.com --- 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;
On Thu, Jun 6, 2019 at 8:56 AM Naohiro Aota naohiro.aota@wdc.com wrote:
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).
Are you planning on submitting a patch for the test case as well, so that it writes at least 4Mb? Would be useful to have.
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+ Signed-off-by: Naohiro Aota naohiro.aota@wdc.com
Reviewed-by: Filipe Manana fdmanana@suse.com
Looks good, thanks.
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
On Thu, Jun 06, 2019 at 04:54:44PM +0900, Naohiro Aota wrote:
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+ Signed-off-by: Naohiro Aota naohiro.aota@wdc.com
Thanks, added to misc-next.
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