zram: preparation for multi-zcomp support

Patch series "zram: Support multiple compression streams", v5.

This series adds support for multiple compression streams.  The main idea
is that different compression algorithms have different characteristics
and zram may benefit when it uses a combination of algorithms: a default
algorithm that is faster but have lower compression rate and a secondary
algorithm that can use higher compression rate at a price of slower
compression/decompression.

There are several use-case for this functionality:

- huge pages re-compression: zstd or deflate can successfully compress
  huge pages (~50% of huge pages on my synthetic ChromeOS tests), IOW
  pages that lzo was not able to compress.

- idle pages re-compression: idle/cold pages sit in the memory and we
  may reduce zsmalloc memory usage if we recompress those idle pages.

Userspace has a number of ways to control the behavior and impact of zram
recompression: what type of pages should be recompressed, size watermarks,
etc.  Please refer to documentation patch.

This patch (of 13):

The patch turns compression streams and compressor algorithm name struct
zram members into arrays, so that we can have multiple compression streams
support (in the next patches).

The patch uses a rather explicit API for compressor selection:

- Get primary (default) compression stream
	zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP])
- Get secondary compression stream
	zcomp_stream_get(zram->comps[ZRAM_SECONDARY_COMP])

We use similar API for compression streams put().

At this point we always have just one compression stream,
since CONFIG_ZRAM_MULTI_COMP is not yet defined.

Link: https://lkml.kernel.org/r/20221109115047.2921851-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20221109115047.2921851-2-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 0916de952e091e2e38116bb548d84b127fcc0569..55af4efd79835666a857884a992ba37c2d7d3a08 100644 (file)
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -206,7 +206,7 @@ void zcomp_destroy(struct zcomp *comp)
  * case of allocation error, or any other error potentially
  * returned by zcomp_init().
  */
-struct zcomp *zcomp_create(const char *compress)
+struct zcomp *zcomp_create(const char *alg)
 {
        struct zcomp *comp;
        int error;
@@ -216,14 +216,14 @@ struct zcomp *zcomp_create(const char *compress)
         * is not loaded yet. We must do it here, otherwise we are about to
         * call /sbin/modprobe under CPU hot-plug lock.
         */
-       if (!zcomp_available_algorithm(compress))
+       if (!zcomp_available_algorithm(alg))
                return ERR_PTR(-EINVAL);
 
        comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL);
        if (!comp)
                return ERR_PTR(-ENOMEM);
 
-       comp->name = compress;
+       comp->name = alg;
        error = zcomp_init(comp);
        if (error) {
                kfree(comp);

diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index 40f6420f4b2e92d6129e4ba37c9daa5b3e229810..cdefdef93da8c00d3086e10c0980f7c5462694e8 100644 (file)
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -27,7 +27,7 @@ int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node);
 ssize_t zcomp_available_show(const char *comp, char *buf);
 bool zcomp_available_algorithm(const char *comp);
 
-struct zcomp *zcomp_create(const char *comp);
+struct zcomp *zcomp_create(const char *alg);
 void zcomp_destroy(struct zcomp *comp);
 
 struct zcomp_strm *zcomp_stream_get(struct zcomp *comp);

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 87711ddf4b54b710967909de91f1aaab0b89dcee..fbe46c6177fd79c24c94a9f84bb58797e8c10455 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1004,36 +1004,53 @@ static ssize_t comp_algorithm_show(struct device *dev,
        struct zram *zram = dev_to_zram(dev);
 
        down_read(&zram->init_lock);
-       sz = zcomp_available_show(zram->compressor, buf);
+       sz = zcomp_available_show(zram->comp_algs[ZRAM_PRIMARY_COMP], buf);
        up_read(&zram->init_lock);
 
        return sz;
 }
 
+static void comp_algorithm_set(struct zram *zram, u32 prio, const char *alg)
+{
+       /* Do not kfree() algs that we didn't allocate, IOW the default ones */
+       if (zram->comp_algs[prio] != default_compressor)
+               kfree(zram->comp_algs[prio]);
+       zram->comp_algs[prio] = alg;
+}
+
 static ssize_t comp_algorithm_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t len)
 {
        struct zram *zram = dev_to_zram(dev);
-       char compressor[ARRAY_SIZE(zram->compressor)];
+       char *compressor;
        size_t sz;
 
-       strscpy(compressor, buf, sizeof(compressor));
+       sz = strlen(buf);
+       if (sz >= CRYPTO_MAX_ALG_NAME)
+               return -E2BIG;
+
+       compressor = kstrdup(buf, GFP_KERNEL);
+       if (!compressor)
+               return -ENOMEM;
+
        /* ignore trailing newline */
-       sz = strlen(compressor);
        if (sz > 0 && compressor[sz - 1] == '\n')
                compressor[sz - 1] = 0x00;
 
-       if (!zcomp_available_algorithm(compressor))
+       if (!zcomp_available_algorithm(compressor)) {
+               kfree(compressor);
                return -EINVAL;
+       }
 
        down_write(&zram->init_lock);
        if (init_done(zram)) {
                up_write(&zram->init_lock);
+               kfree(compressor);
                pr_info("Can't change algorithm for initialized device\n");
                return -EBUSY;
        }
 
-       strcpy(zram->compressor, compressor);
+       comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, compressor);
        up_write(&zram->init_lock);
        return len;
 }
@@ -1281,7 +1298,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
        size = zram_get_obj_size(zram, index);
 
        if (size != PAGE_SIZE)
-               zstrm = zcomp_stream_get(zram->comp);
+               zstrm = zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]);
 
        src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
        if (size == PAGE_SIZE) {
@@ -1293,7 +1310,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
                dst = kmap_atomic(page);
                ret = zcomp_decompress(zstrm, src, size, dst);
                kunmap_atomic(dst);
-               zcomp_stream_put(zram->comp);
+               zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
        }
        zs_unmap_object(zram->mem_pool, handle);
        zram_slot_unlock(zram, index);
@@ -1360,13 +1377,13 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
        kunmap_atomic(mem);
 
 compress_again:
-       zstrm = zcomp_stream_get(zram->comp);
+       zstrm = zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]);
        src = kmap_atomic(page);
        ret = zcomp_compress(zstrm, src, &comp_len);
        kunmap_atomic(src);
 
        if (unlikely(ret)) {
-               zcomp_stream_put(zram->comp);
+               zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
                pr_err("Compression failed! err=%d\n", ret);
                zs_free(zram->mem_pool, handle);
                return ret;
@@ -1394,7 +1411,7 @@ compress_again:
                                __GFP_HIGHMEM |
                                __GFP_MOVABLE);
        if (IS_ERR((void *)handle)) {
-               zcomp_stream_put(zram->comp);
+               zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
                atomic64_inc(&zram->stats.writestall);
                handle = zs_malloc(zram->mem_pool, comp_len,
                                GFP_NOIO | __GFP_HIGHMEM |
@@ -1411,14 +1428,14 @@ compress_again:
                 * zstrm buffer back. It is necessary that the dereferencing
                 * of the zstrm variable below occurs correctly.
                 */
-               zstrm = zcomp_stream_get(zram->comp);
+               zstrm = zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]);
        }
 
        alloced_pages = zs_get_total_pages(zram->mem_pool);
        update_used_max(zram, alloced_pages);
 
        if (zram->limit_pages && alloced_pages > zram->limit_pages) {
-               zcomp_stream_put(zram->comp);
+               zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
                zs_free(zram->mem_pool, handle);
                return -ENOMEM;
        }
@@ -1432,7 +1449,7 @@ compress_again:
        if (comp_len == PAGE_SIZE)
                kunmap_atomic(src);
 
-       zcomp_stream_put(zram->comp);
+       zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
        zs_unmap_object(zram->mem_pool, handle);
        atomic64_add(comp_len, &zram->stats.compr_data_size);
 out:
@@ -1707,6 +1724,20 @@ out:
        return ret;
 }
 
+static void zram_destroy_comps(struct zram *zram)
+{
+       u32 prio;
+
+       for (prio = 0; prio < ZRAM_MAX_COMPS; prio++) {
+               struct zcomp *comp = zram->comps[prio];
+
+               zram->comps[prio] = NULL;
+               if (!comp)
+                       continue;
+               zcomp_destroy(comp);
+       }
+}
+
 static void zram_reset_device(struct zram *zram)
 {
        down_write(&zram->init_lock);
@@ -1724,11 +1755,11 @@ static void zram_reset_device(struct zram *zram)
        /* I/O operation under all of CPU are done so let's free */
        zram_meta_free(zram, zram->disksize);
        zram->disksize = 0;
+       zram_destroy_comps(zram);
        memset(&zram->stats, 0, sizeof(zram->stats));
-       zcomp_destroy(zram->comp);
-       zram->comp = NULL;
        reset_bdev(zram);
 
+       comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
        up_write(&zram->init_lock);
 }
 
@@ -1739,6 +1770,7 @@ static ssize_t disksize_store(struct device *dev,
        struct zcomp *comp;
        struct zram *zram = dev_to_zram(dev);
        int err;
+       u32 prio;
 
        disksize = memparse(buf, NULL);
        if (!disksize)
@@ -1757,22 +1789,28 @@ static ssize_t disksize_store(struct device *dev,
                goto out_unlock;
        }
 
-       comp = zcomp_create(zram->compressor);
-       if (IS_ERR(comp)) {
-               pr_err("Cannot initialise %s compressing backend\n",
-                               zram->compressor);
-               err = PTR_ERR(comp);
-               goto out_free_meta;
-       }
+       for (prio = 0; prio < ZRAM_MAX_COMPS; prio++) {
+               if (!zram->comp_algs[prio])
+                       continue;
+
+               comp = zcomp_create(zram->comp_algs[prio]);
+               if (IS_ERR(comp)) {
+                       pr_err("Cannot initialise %s compressing backend\n",
+                              zram->comp_algs[prio]);
+                       err = PTR_ERR(comp);
+                       goto out_free_comps;
+               }
 
-       zram->comp = comp;
+               zram->comps[prio] = comp;
+       }
        zram->disksize = disksize;
        set_capacity_and_notify(zram->disk, zram->disksize >> SECTOR_SHIFT);
        up_write(&zram->init_lock);
 
        return len;
 
-out_free_meta:
+out_free_comps:
+       zram_destroy_comps(zram);
        zram_meta_free(zram, disksize);
 out_unlock:
        up_write(&zram->init_lock);
@@ -1959,7 +1997,7 @@ static int zram_add(void)
        if (ret)
                goto out_cleanup_disk;
 
-       strscpy(zram->compressor, default_compressor, sizeof(zram->compressor));
+       zram->comp_algs[ZRAM_PRIMARY_COMP] = default_compressor;
 
        zram_debugfs_register(zram);
        pr_info("Added device: %s\n", zram->disk->disk_name);

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index a2bda53020fddeb42d8b053abd68da8b91cf8f86..7a643c8c38ecaeaba8717cc64f907da63025bdcf 100644 (file)
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -89,10 +89,20 @@ struct zram_stats {
 #endif
 };
 
+#ifdef CONFIG_ZRAM_MULTI_COMP
+#define ZRAM_PRIMARY_COMP      0U
+#define ZRAM_SECONDARY_COMP    1U
+#define ZRAM_MAX_COMPS 4U
+#else
+#define ZRAM_PRIMARY_COMP      0U
+#define ZRAM_SECONDARY_COMP    0U
+#define ZRAM_MAX_COMPS 1U
+#endif
+
 struct zram {
        struct zram_table_entry *table;
        struct zs_pool *mem_pool;
-       struct zcomp *comp;
+       struct zcomp *comps[ZRAM_MAX_COMPS];
        struct gendisk *disk;
        /* Prevent concurrent execution of device init */
        struct rw_semaphore init_lock;
@@ -107,7 +117,7 @@ struct zram {
         * we can store in a disk.
         */
        u64 disksize;   /* bytes */
-       char compressor[CRYPTO_MAX_ALG_NAME];
+       const char *comp_algs[ZRAM_MAX_COMPS];
        /*
         * zram is claimed so open request will be failed
         */