Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

[Rui Salvaterra]

Hi,

After commit 744889b7cbb56a64f957e65ade7cb65fe3f35714, I started
getting this (-EIO, it seems) on my dmesg:

swapon: discard_swap(00000000c275f02d): -5

This is an 8 GB zram swap device. It's configured like this:

modprobe zram
echo zstd > /sys/block/zram0/comp_algorithm
echo 8297508864 > /sys/block/zram0/disksize
mkswap /dev/zram0
swapon -d -p 100 /dev/zram0

I should note that if I use --discard=pages instead of -d (both
policies) at swapon, I don't get this error.
Reverting the commit from v4.19 final fixes the error for me, but
surely breaks something else. :)
Let me know if you need any additional information.

Thanks,

Rui

Re: Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

[Ming Lei]

On Thu, Oct 25, 2018 at 05:09:32PM +0100, Rui Salvaterra wrote:
> Hi,
> 
> After commit 744889b7cbb56a64f957e65ade7cb65fe3f35714, I started
> getting this (-EIO, it seems) on my dmesg:
> 
> swapon: discard_swap(00000000c275f02d): -5
> 
> This is an 8 GB zram swap device. It's configured like this:
> 
> modprobe zram
> echo zstd > /sys/block/zram0/comp_algorithm
> echo 8297508864 > /sys/block/zram0/disksize
> mkswap /dev/zram0
> swapon -d -p 100 /dev/zram0
> 
> I should note that if I use --discard=pages instead of -d (both
> policies) at swapon, I don't get this error.
> Reverting the commit from v4.19 final fixes the error for me, but
> surely breaks something else. :)
> Let me know if you need any additional information.

The reason is that zram doesn't call blk_queue_split() in .make_request_fn, :-(

Then the similar logic in blk_queue_split() has to be duplicated somewhere,
such as __blkdev_issue_discard().

I will post a patch for you soon.

Thanks,
Ming

Re: Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

[Ming Lei]

On Thu, Oct 25, 2018 at 05:09:32PM +0100, Rui Salvaterra wrote:
> Hi,
> 
> After commit 744889b7cbb56a64f957e65ade7cb65fe3f35714, I started
> getting this (-EIO, it seems) on my dmesg:
> 
> swapon: discard_swap(00000000c275f02d): -5
> 
> This is an 8 GB zram swap device. It's configured like this:
> 
> modprobe zram
> echo zstd > /sys/block/zram0/comp_algorithm
> echo 8297508864 > /sys/block/zram0/disksize
> mkswap /dev/zram0
> swapon -d -p 100 /dev/zram0
> 
> I should note that if I use --discard=pages instead of -d (both
> policies) at swapon, I don't get this error.
> Reverting the commit from v4.19 final fixes the error for me, but
> surely breaks something else. :)
> Let me know if you need any additional information.

The patch titled with 'block: make sure discard bio is aligned with logical block size'
in the list may fix this issue, please test and see if it works.

Thanks,
Ming

Re: Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

[Rui Salvaterra]

On Fri, 26 Oct 2018 at 07:27, Ming Lei <ming.lei@redhat.com> wrote:
>
> The patch titled with 'block: make sure discard bio is aligned with logical block size'
> in the list may fix this issue, please test and see if it works.
>
> Thanks,
> Ming

Hi, Ming,

Thanks for the quick reply. Unfortunately, it doesn't seem to apply
cleanly to 4.19. To which tree/tag/commit should I apply the series?

Thanks,

Rui

Re: Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

[Ming Lei]

On Fri, Oct 26, 2018 at 08:50:20AM +0100, Rui Salvaterra wrote:
> On Fri, 26 Oct 2018 at 07:27, Ming Lei <ming.lei@redhat.com> wrote:
> >
> > The patch titled with 'block: make sure discard bio is aligned with logical block size'
> > in the list may fix this issue, please test and see if it works.
> >
> > Thanks,
> > Ming
> 
> Hi, Ming,
> 
> Thanks for the quick reply. Unfortunately, it doesn't seem to apply
> cleanly to 4.19. To which tree/tag/commit should I apply the series?

The whole patchset is against linus tree (44786880df196a4200).

I am sure that the 1st patch can be applied cleanly against v4.19, and
it is enough for fixing this issue, please double check.

[ming@ming linux]$ git log --oneline -1
84df9525b0c2 Linux 4.19
[ming@ming linux]$ git am ~/emails/blk/181026\ \[PATCH\ 1∕3\]\ block\:\ make\ sure\ discard\ bio\ is\ aligned\ with\ logical\ block\ size.eml
Applying: block: make sure discard bio is aligned with logical block size
[ming@ming linux]$ 


Thanks,
Ming

Re: Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

[Rui Salvaterra]

On Sun, 28 Oct 2018 at 01:02, Ming Lei <ming.lei@redhat.com> wrote:
>
> On Fri, Oct 26, 2018 at 08:50:20AM +0100, Rui Salvaterra wrote:
> > On Fri, 26 Oct 2018 at 07:27, Ming Lei <ming.lei@redhat.com> wrote:
> > >
> > > The patch titled with 'block: make sure discard bio is aligned with l=
ogical block size'
> > > in the list may fix this issue, please test and see if it works.
> > >
> > > Thanks,
> > > Ming
> >
> > Hi, Ming,
> >
> > Thanks for the quick reply. Unfortunately, it doesn't seem to apply
> > cleanly to 4.19. To which tree/tag/commit should I apply the series?
>
> The whole patchset is against linus tree (44786880df196a4200).
>
> I am sure that the 1st patch can be applied cleanly against v4.19, and
> it is enough for fixing this issue, please double check.
>
> [ming@ming linux]$ git log --oneline -1
> 84df9525b0c2 Linux 4.19
> [ming@ming linux]$ git am ~/emails/blk/181026\ \[PATCH\ 1=E2=88=953\]\ bl=
ock\:\ make\ sure\ discard\ bio\ is\ aligned\ with\ logical\ block\ size.em=
l
> Applying: block: make sure discard bio is aligned with logical block size
> [ming@ming linux]$
>
>
> Thanks,
> Ming

Hi, Ming,

You're, right, of course. I had reverted the aforementioned commit, so
the patch set obviously wouldn't apply anymore. After checking out
v4.19 again, everything went smoothly. I confirm the patch set fixes
the issue for me, which means this series is

Tested-by: Rui Salvaterra <rsalvaterra@gmail.com>

Thanks again,

Rui

Re: Bug: swap discard issue with zram caused by "block: don't deal with discard limit in blkdev_issue_discard()"

[Rui Salvaterra]

On Sun, 28 Oct 2018 at 01:02, Ming Lei <ming.lei@redhat.com> wrote:
>
> On Fri, Oct 26, 2018 at 08:50:20AM +0100, Rui Salvaterra wrote:
> > On Fri, 26 Oct 2018 at 07:27, Ming Lei <ming.lei@redhat.com> wrote:
> > >
> > > The patch titled with 'block: make sure discard bio is aligned with logical block size'
> > > in the list may fix this issue, please test and see if it works.
> > >
> > > Thanks,
> > > Ming
> >
> > Hi, Ming,
> >
> > Thanks for the quick reply. Unfortunately, it doesn't seem to apply
> > cleanly to 4.19. To which tree/tag/commit should I apply the series?
>
> The whole patchset is against linus tree (44786880df196a4200).
>
> I am sure that the 1st patch can be applied cleanly against v4.19, and
> it is enough for fixing this issue, please double check.
>
> [ming@ming linux]$ git log --oneline -1
> 84df9525b0c2 Linux 4.19
> [ming@ming linux]$ git am ~/emails/blk/181026\ \[PATCH\ 1∕3\]\ block\:\ make\ sure\ discard\ bio\ is\ aligned\ with\ logical\ block\ size.eml
> Applying: block: make sure discard bio is aligned with logical block size
> [ming@ming linux]$
>
>
> Thanks,
> Ming

Hi, Ming,

You're, right, of course. I had reverted the aforementioned commit, so
the patch set obviously wouldn't apply anymore. After checking out
v4.19 again, everything went smoothly. I confirm the patch set fixes
the issue for me, which means this series is

Tested-by: Rui Salvaterra <rsalvaterra@gmail.com>

Thanks again,

Rui