[RFC PATCHv5 0/6] zram: introduce writeback bio batching

[Sergey Senozhatsky]

RFC

This is a different approach compared to [1].  Instead of
using blk plug API to batch writeback bios, we just keep
submitting them and track available of done/idle requests
(we still use a pool of requests, to put a constraint on
memory usage).  The intuition is that blk plug API is good
for sequential IO patterns, but zram writeback is more
likely to use random IO patterns.

I only did minimal testing so far (in a VM).  More testing
(on real H/W) is needed, any help is highly appreciated.

[1] https://lore.kernel.org/linux-kernel/20251118073000.1928107-1-senozhatsky@xxxxxxxxxxxx

v3 -> v4:
- do not use blk plug API

Sergey Senozhatsky (6):
  zram: introduce writeback bio batching
  zram: add writeback batch size device attr
  zram: take write lock in wb limit store handlers
  zram: drop wb_limit_lock
  zram: rework bdev block allocation
  zram: read slot block idx under slot lock

 drivers/block/zram/zram_drv.c | 470 ++++++++++++++++++++++++++--------
 drivers/block/zram/zram_drv.h |   2 +-
 2 files changed, 364 insertions(+), 108 deletions(-)

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2.52.0.rc1.455.g30608eb744-goog