* [PATCH] btrfs: start readahead also in seed devices
@ 2019-06-06 7:54 Naohiro Aota
2019-06-06 11:14 ` Filipe Manana
2019-06-07 13:39 ` David Sterba
0 siblings, 2 replies; 4+ messages in thread
From: Naohiro Aota @ 2019-06-06 7:54 UTC (permalink / raw)
To: linux-btrfs; +Cc: David Sterba, Naohiro Aota, stable
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;
--
2.21.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] btrfs: start readahead also in seed devices
2019-06-06 7:54 [PATCH] btrfs: start readahead also in seed devices Naohiro Aota
@ 2019-06-06 11:14 ` Filipe Manana
2019-06-07 2:29 ` Naohiro Aota
2019-06-07 13:39 ` David Sterba
1 sibling, 1 reply; 4+ messages in thread
From: Filipe Manana @ 2019-06-06 11:14 UTC (permalink / raw)
To: Naohiro Aota; +Cc: linux-btrfs, David Sterba, stable
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
>
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] btrfs: start readahead also in seed devices
2019-06-06 11:14 ` Filipe Manana
@ 2019-06-07 2:29 ` Naohiro Aota
0 siblings, 0 replies; 4+ messages in thread
From: Naohiro Aota @ 2019-06-07 2:29 UTC (permalink / raw)
To: fdmanana; +Cc: linux-btrfs, David Sterba
On 2019/06/06 20:14, Filipe Manana wrote:
> 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.
I will send that patch soon.
Thanks,
>
>>
>> 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
>>
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] btrfs: start readahead also in seed devices
2019-06-06 7:54 [PATCH] btrfs: start readahead also in seed devices Naohiro Aota
2019-06-06 11:14 ` Filipe Manana
@ 2019-06-07 13:39 ` David Sterba
1 sibling, 0 replies; 4+ messages in thread
From: David Sterba @ 2019-06-07 13:39 UTC (permalink / raw)
To: Naohiro Aota; +Cc: linux-btrfs, David Sterba, stable
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.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-06-06 11:14 ` Filipe Manana
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2019-06-07 13:39 ` David Sterba
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