NACK/Cmnt: [SRU][B][F][G][PATCH 0/1] dm crypt: add flags to optionally

[Gerald Yang]

Hi Stefan,

I checked and also tried to backport these commits:
git log --oneline --grep "Fixes: 39d42fa96ba1"
c87a95dc28b1 dm crypt: defer decryption to a tasklet if interrupts disabled
8e14f610159d dm crypt: do not call bio_endio() from the dm-crypt tasklet
d68b29584c25 dm crypt: use GFP_ATOMIC when allocating crypto requests from
softirq
8abec36d1274 dm crypt: do not wait for backlogged crypto request completion
in
softirq
4a5caa4af0df dm crypt: document new no_workqueue flags

But it failed to build the kernel, I found there are more dependencies need
to be backported
Take focal kernel (5.4) for instance, the build error is:
/home/ubuntu/focal/drivers/md/dm-crypt.c:2768:8: error:
‘dm_report_zones_cb’ undeclared (first use in this function); did you mean
‘dm_report_zones_fn’?
2768 | dm_report_zones_cb, args);

This function "dm_report_zones_cb" was introduced in this commit in 5.5
kernel:
git log -L :dm_report_zones_cb:drivers/md/dm.c
commit d41003513e61dd9d4974cb441d30b63650b85654
git describe --contains d41003513e61dd9d4974cb441d30b63650b85654
v5.5-rc1~199^2~1

It reworked "zone reporting"
d41003513e61 block: rework zone reporting

And modify some other files in block layer
drivers/md/dm-flakey.c
drivers/md/dm-linear.c
drivers/scsi/sd.h
fs/f2fs/super.c
include/linux/device-mapper.h
block/blk-zoned.c
drivers/block/null_blk.h
drivers/block/null_blk_zoned.c
drivers/md/dm-zoned-metadata.c
drivers/md/dm.c
drivers/scsi/sd_zbc.c
include/linux/blkdev.h

I think it could get more dependencies involved for backporting this commit

And the original commit I wanted to backport
(39d42fa96ba1b7d2544db3f8ed5da8fb0d5cb877)
changes dm-crypt version from 1.19.0 to 1.22.0 for focal kernel (5.4)

Because this is a request from our customer, I would like to ask for advice
if it's still proper to backport this one and all related commits?
or it's better to wait for a newer hwe kernel that has this commit included?

Thanks,
Gerald

On Wed, May 19, 2021 at 3:26 PM Gerald Yang <gerald.yang at canonical.com>
wrote:

> Thanks Stefan, I will update the SRU with all related commits
>
> On Tue, May 18, 2021 at 2:42 PM Stefan Bader <stefan.bader at canonical.com>
> wrote:
>
>> On 18.05.21 04:56, Gerald Yang wrote:
>> > BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1910976
>>
>> Above should be https://bugs.launchpad.net/bugs/1910976 but that could
>> be done
>> when applying. However there seem to be multiple references to this patch
>> following its introduction upstream (see below). That does not sound like
>> just
>> picking this one patch is a good idea.
>>
>> -Stefan
>>
>> >
>> > === SRU Justification ===
>> > [Impact]
>> > To get better performance for dm-crypt in some cases, bypass kcryptd
>> > workqueue can reduce the overhead in context switch between kworkers,
>> > cherry-pick commit 39d42fa96ba1b7d2544db3f8ed5da8fb0d5cb877 from
>> mainline
>> > kernel, and bypass kcryptd workqueue is not enabled by default
>> >
>> > [Fix]
>> > Add flags to bypass kcryptd workqueue
>> >
>> > [Test]
>> > create dm-crypt and setup DM_CRYPT_NO_READ_WORKQUEUE and
>> > DM_CRYPT_NO_WRITE_WORKQUEUE, read/write data and run perf record to see
>> > if read/write to the encrypted device will bypass kcryptd workqueue
>> >
>> > [Regression Potential]
>> > Low, this feature is disabled by default, need to enable manually
>> >
>> > Ignat Korchagin (1):
>> >    dm crypt: add flags to optionally bypass kcryptd workqueues
>> >
>> >   drivers/md/dm-crypt.c | 50 ++++++++++++++++++++++++++++++++++++-------
>> >   1 file changed, 42 insertions(+), 8 deletions(-)
>> >
>>
>>  > git log --oneline --grep "Fixes: 39d42fa96ba1"
>> c87a95dc28b1 dm crypt: defer decryption to a tasklet if interrupts
>> disabled
>> 8e14f610159d dm crypt: do not call bio_endio() from the dm-crypt tasklet
>> d68b29584c25 dm crypt: use GFP_ATOMIC when allocating crypto requests
>> from softirq
>> 8abec36d1274 dm crypt: do not wait for backlogged crypto request
>> completion in
>> softirq
>> 4a5caa4af0df dm crypt: document new no_workqueue flags
>>
>>
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