linux-stable.git/drivers/block/zram, branch v6.2.3

zram: remove unused stats fields

2022-11-30T23:59:01+00:00

We don't show num_reads and num_writes since we removed corresponding
sysfs nodes in 2017.  Block layer stats are exposed via
/sys/block/zramX/stat file.

However, we still increment those atomic vars and store them in zram
stats.  Remove leftovers.

Link: https://lkml.kernel.org/r/20221117141326.1105181-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Nitin Gupta 
Signed-off-by: Andrew Morton

zram: add incompressible flag to read_block_state()

2022-11-30T23:58:53+00:00

Add a new flag to zram block state that shows if the page is
incompressible: that none of the algorithm (including secondary ones)
could compress it.

Link: https://lkml.kernel.org/r/20221109115047.2921851-14-senozhatsky@chromium.org
Suggested-by: Minchan Kim 
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: add incompressible writeback

2022-11-30T23:58:53+00:00

Add support for incompressible pages writeback:

  echo incompressible > /sys/block/zramX/writeback

Link: https://lkml.kernel.org/r/20221109115047.2921851-13-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: add algo parameter support to zram_recompress()

2022-11-30T23:58:52+00:00

Recompression iterates through all the registered secondary compression
algorithms in order of their priorities so that we have higher chances of
finding the algorithm that compresses a particular page.  This, however,
may not always be best approach and sometimes we may want to limit
recompression to only one particular algorithm.  For instance, when a
higher priority algorithm uses too much power and device has a relatively
low battery level we may want to limit recompression to use only a lower
priority algorithm, which uses less power.

Introduce algo= parameter support to recompression sysfs knob so that
user-sapce can request recompression with particular algorithm only:

  echo "type=idle algo=zstd" > /sys/block/zramX/recompress

Link: https://lkml.kernel.org/r/20221109115047.2921851-11-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: remove redundant checks from zram_recompress()

2022-11-30T23:58:52+00:00

Size class index comparison is powerful enough so we can remove object
size comparisons.

Link: https://lkml.kernel.org/r/20221109115047.2921851-10-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: add size class equals check into recompression

2022-11-30T23:58:52+00:00

It makes no sense for us to recompress the object if it will be in the
same size class.  We anyway don't get any memory gain.  But, at the same
time, we get a CPU time overhead when inserting this object into zspage
and decompressing it afterwards.

[senozhatsky: rebased and fixed conflicts]
Link: https://lkml.kernel.org/r/20221109115047.2921851-9-senozhatsky@chromium.org
Signed-off-by: Alexey Romanov 
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: use IS_ERR_VALUE() to check for zs_malloc() errors

2022-11-30T23:58:52+00:00

Avoid typecasts that are needed for IS_ERR() and use IS_ERR_VALUE()
instead.

Link: https://lkml.kernel.org/r/20221109115047.2921851-8-senozhatsky@chromium.org
Suggested-by: Andrew Morton 
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: clarify writeback_store() comment

2022-11-30T23:58:52+00:00

Re-phrase writeback BIO error comment.

Link: https://lkml.kernel.org/r/20221109115047.2921851-7-senozhatsky@chromium.org
Reported-by: Andrew Morton 
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: add recompress flag to read_block_state()

2022-11-30T23:58:51+00:00

Add a new flag to zram block state that shows if the page was recompressed
(using alternative compression algorithm).

Link: https://lkml.kernel.org/r/20221109115047.2921851-6-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: introduce recompress sysfs knob

2022-11-30T23:58:51+00:00

Allow zram to recompress (using secondary compression streams)
pages.

Re-compression algorithms (we support up to 3 at this stage)
are selected via recomp_algorithm:

  echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm

Please read documentation for more details.

We support several recompression modes:

1) IDLE pages recompression is activated by `idle` mode

  echo "type=idle" > /sys/block/zram0/recompress

2) Since there may be many idle pages user-space may pass a size
threshold value (in bytes) and we will recompress pages only
of equal or greater size:

  echo "threshold=888" > /sys/block/zram0/recompress

3) HUGE pages recompression is activated by `huge` mode

  echo "type=huge" > /sys/block/zram0/recompress

4) HUGE_IDLE pages recompression is activated by `huge_idle` mode

  echo "type=huge_idle" > /sys/block/zram0/recompress

[senozhatsky@chromium.org: we should always zero out err variable in recompress loop[
  Link: https://lkml.kernel.org/r/20221110143423.3250790-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20221109115047.2921851-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Nathan Chancellor 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton