kernel/linux.git/drivers/block/zram/zcomp.h, branch linux-7.1.y

zram: use statically allocated compression algorithm names

2026-04-05T20:53:07+00:00

Currently, zram dynamically allocates memory for compressor algorithm names when they are set by the user. This requires careful memory management, including explicit `kfree` calls and special handling to avoid freeing statically defined default compressor names. This patch refactors the way zram handles compression algorithm names. Instead of storing dynamically allocated copies, `zram->comp_algs` will now store pointers directly to the static name strings defined within the `zcomp_ops` backend structures, thereby removing the need for conditional `kfree` calls. Link: https://lkml.kernel.org/r/5bb2e9318d124dbcb2b743dcdce6a950@honor.com Signed-off-by: gao xu Reviewed-by: Sergey Senozhatsky Cc: Jens Axboe Cc: Minchan Kim Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton

zram: pass buffer offset to zcomp_available_show()

2025-07-04T01:56:51+00:00

In most cases zcomp_available_show() is the only emitting function that is called from sysfs read() handler, so it assumes that there is a whole PAGE_SIZE buffer to work with. There is an exception, however: recomp_algorithm_show(). In recomp_algorithm_show() we prepend the buffer with priority number before we pass it to zcomp_available_show(), so it cannot assume PAGE_SIZE anymore and must take recomp_algorithm_show() modifications into consideration. Therefore we need to pass buffer offset to zcomp_available_show(). Also convert it to use sysfs_emit_at(), to stay aligned with the rest of zram's sysfs read() handlers. On practice we are never even close to using the whole PAGE_SIZE buffer, so that's not a critical bug, but still. Signed-off-by: Sergey Senozhatsky Link: https://lore.kernel.org/r/20250627071840.1394242-1-senozhatsky@chromium.org Signed-off-by: Jens Axboe

zram: support deflate-specific params

2025-06-01T05:46:07+00:00

Introduce support of algorithm specific parameters in algorithm_params device attribute. The expected format is algorithm.param=value. For starters, add support for deflate.winbits parameter. Link: https://lkml.kernel.org/r/20250514024825.1745489-3-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Reviewed-by: Mikhail Zaslonko Cc: Minchan Kim Signed-off-by: Andrew Morton

zram: rename ZCOMP_PARAM_NO_LEVEL

2025-06-01T05:46:07+00:00

Patch series "zram: support algorithm-specific parameters". This patchset adds support for algorithm-specific parameters. For now, only deflate-specific winbits can be configured, which fixes deflate support on some s390 setups. This patch (of 2): Use more generic name because this will be default "un-set" value for more params in the future. Link: https://lkml.kernel.org/r/20250514024825.1745489-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20250514024825.1745489-2-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Reviewed-by: Mikhail Zaslonko Cc: Minchan Kim Signed-off-by: Andrew Morton

zram: switch to new zsmalloc object mapping API

2025-03-17T05:06:36+00:00

Use new read/write zsmalloc object API. For cases when RO mapped object spans two physical pages (requires temp buffer) compression streams now carry around one extra physical page. Link: https://lkml.kernel.org/r/20250303022425.285971-16-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Cc: Hillf Danton Cc: Kairui Song Cc: Minchan Kim Cc: Sebastian Andrzej Siewior Cc: Yosry Ahmed Signed-off-by: Andrew Morton

zram: permit preemption with active compression stream

2025-03-17T05:06:33+00:00

Currently, per-CPU stream access is done from a non-preemptible (atomic) section, which imposes the same atomicity requirements on compression backends as entry spin-lock, and makes it impossible to use algorithms that can schedule/wait/sleep during compression and decompression. Switch to preemptible per-CPU model, similar to the one used in zswap. Instead of a per-CPU local lock, each stream carries a mutex which is locked throughout entire time zram uses it for compression or decompression, so that cpu-dead event waits for zram to stop using a particular per-CPU stream and release it. Link: https://lkml.kernel.org/r/20250303022425.285971-3-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Suggested-by: Yosry Ahmed Reviewed-by: Yosry Ahmed Cc: Hillf Danton Cc: Kairui Song Cc: Minchan Kim Cc: Sebastian Andrzej Siewior Signed-off-by: Andrew Morton

zram: move immutable comp params away from per-CPU context

2024-09-09T23:39:10+00:00

Immutable params never change once comp has been allocated and setup, so we don't need to store multiple copies of them in each per-CPU backend context. Move those to per-comp zcomp_params and pass it to backends callbacks for requests execution. Basically, this means parameters sharing between different contexts. Also introduce two new backends callbacks: setup_params() and release_params(). First, we need to validate params in a driver-specific way; second, driver may want to allocate its specific representation of the params which is needed to execute requests. Link: https://lkml.kernel.org/r/20240902105656.1383858-20-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Cc: Minchan Kim Cc: Nick Terrell Signed-off-by: Andrew Morton

zram: introduce zcomp_ctx structure

2024-09-09T23:39:10+00:00

Keep run-time driver data (scratch buffers, etc.) in zcomp_ctx structure. This structure is allocated per-CPU because drivers (backends) need to modify its content during requests execution. We will split mutable and immutable driver data, this is a preparation path. Link: https://lkml.kernel.org/r/20240902105656.1383858-19-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Cc: Minchan Kim Cc: Nick Terrell Signed-off-by: Andrew Morton

zram: introduce zcomp_req structure

2024-09-09T23:39:10+00:00

Encapsulate compression/decompression data in zcomp_req structure. Link: https://lkml.kernel.org/r/20240902105656.1383858-18-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Cc: Minchan Kim Cc: Nick Terrell Signed-off-by: Andrew Morton

zram: introduce zcomp_params structure

2024-09-09T23:39:09+00:00

We will store a per-algorithm parameters there (compression level, dictionary, dictionary size, etc.). Link: https://lkml.kernel.org/r/20240902105656.1383858-14-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Cc: Minchan Kim Cc: Nick Terrell Signed-off-by: Andrew Morton