zram: introduce algorithm_params device attribute

This attribute is used to setup compression algorithms' parameters, so we
can tweak algorithms' characteristics.  At this point only 'level' is
supported (to be extended in the future).

Each call sets up parameters for one particular algorithm, which should be
specified either by the algorithm's priority or algo name.  This is
expected to be called after corresponding algorithm is selected via
comp_algorithm or recomp_algorithm.

 echo "priority=0 level=1" > /sys/block/zram0/algorithm_params
or
 echo "algo=zstd level=1" > /sys/block/zram0/algorithm_params

Link: https://lkml.kernel.org/r/20240902105656.1383858-16-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 628a00fb20a95185870e6acdef03d78cd194d817..1ef69e0271f91dbdedd93795c54f8c5f0e3dc012 100644 (file)
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -151,3 +151,10 @@ Contact:   Sergey Senozhatsky <senozhatsky@chromium.org>
 Description:
                The recompress file is write-only and triggers re-compression
                with secondary compression algorithms.
+
+What:          /sys/block/zram<id>/algorithm_params
+Date:          August 2024
+Contact:       Sergey Senozhatsky <senozhatsky@chromium.org>
+Description:
+               The algorithm_params file is write-only and is used to setup
+               compression algorithm parameters.

diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst
index 181d55d6432600b9347034da76af04aa2c682842..96d81dc12528e2deffd6b58d971b14b86b96361d 100644 (file)
--- a/Documentation/admin-guide/blockdev/zram.rst
+++ b/Documentation/admin-guide/blockdev/zram.rst
@@ -198,6 +198,7 @@ writeback_limit_enable  RW  show and set writeback_limit feature
 max_comp_streams       RW      the number of possible concurrent compress
                                operations
 comp_algorithm         RW      show and change the compression algorithm
+algorithm_params       WO      setup compression algorithm parameters
 compact                WO      trigger memory compaction
 debug_stat             RO      this file is used for zram debugging purposes
 backing_dev            RW      set up backend storage for zram to write out

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index ff6724bbdf912a5281f60adee68cb9f06514878c..e29e952b99c3d2baa894d92479f0c179b4397ce4 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -998,6 +998,72 @@ static int __comp_algorithm_store(struct zram *zram, u32 prio, const char *buf)
        return 0;
 }
 
+static int comp_params_store(struct zram *zram, u32 prio, s32 level)
+{
+       zram->params[prio].level = level;
+       return 0;
+}
+
+static ssize_t algorithm_params_store(struct device *dev,
+                                     struct device_attribute *attr,
+                                     const char *buf,
+                                     size_t len)
+{
+       s32 prio = ZRAM_PRIMARY_COMP, level = ZCOMP_PARAM_NO_LEVEL;
+       char *args, *param, *val, *algo = NULL;
+       struct zram *zram = dev_to_zram(dev);
+       int ret;
+
+       args = skip_spaces(buf);
+       while (*args) {
+               args = next_arg(args, &param, &val);
+
+               if (!val || !*val)
+                       return -EINVAL;
+
+               if (!strcmp(param, "priority")) {
+                       ret = kstrtoint(val, 10, &prio);
+                       if (ret)
+                               return ret;
+                       continue;
+               }
+
+               if (!strcmp(param, "level")) {
+                       ret = kstrtoint(val, 10, &level);
+                       if (ret)
+                               return ret;
+                       continue;
+               }
+
+               if (!strcmp(param, "algo")) {
+                       algo = val;
+                       continue;
+               }
+       }
+
+       /* Lookup priority by algorithm name */
+       if (algo) {
+               s32 p;
+
+               prio = -EINVAL;
+               for (p = ZRAM_PRIMARY_COMP; p < ZRAM_MAX_COMPS; p++) {
+                       if (!zram->comp_algs[p])
+                               continue;
+
+                       if (!strcmp(zram->comp_algs[p], algo)) {
+                               prio = p;
+                               break;
+                       }
+               }
+       }
+
+       if (prio < ZRAM_PRIMARY_COMP || prio >= ZRAM_MAX_COMPS)
+               return -EINVAL;
+
+       ret = comp_params_store(zram, prio, level);
+       return ret ? ret : len;
+}
+
 static ssize_t comp_algorithm_show(struct device *dev,
                                   struct device_attribute *attr,
                                   char *buf)
@@ -2169,6 +2235,7 @@ static DEVICE_ATTR_RW(writeback_limit_enable);
 static DEVICE_ATTR_RW(recomp_algorithm);
 static DEVICE_ATTR_WO(recompress);
 #endif
+static DEVICE_ATTR_WO(algorithm_params);
 
 static struct attribute *zram_disk_attrs[] = {
        &dev_attr_disksize.attr,
@@ -2196,6 +2263,7 @@ static struct attribute *zram_disk_attrs[] = {
        &dev_attr_recomp_algorithm.attr,
        &dev_attr_recompress.attr,
 #endif
+       &dev_attr_algorithm_params.attr,
        NULL,
 };