[PATCH RFC 1/7] zram: Preparation for multi-zcomp support

From: Sergey Senozhatsky
Date: Mon Sep 05 2022 - 04:16:23 EST

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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_ZCOMP])
- Get secondary compression stream
zcomp_stream_get(zram->comps[ZRAM_SECONDARY_ZCOMP])

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.

Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
---
drivers/block/zram/zcomp.c | 6 +--
drivers/block/zram/zcomp.h | 2 +-
drivers/block/zram/zram_drv.c | 87 ++++++++++++++++++++++++-----------
drivers/block/zram/zram_drv.h | 14 +++++-
4 files changed, 77 insertions(+), 32 deletions(-)

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 0916de952e09..55af4efd7983 100644
--- 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 40f6420f4b2e..cdefdef93da8 100644
--- 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 607f4634c27d..4ad1daa1283e 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1018,36 +1018,53 @@ 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_ZCOMP], buf);
up_read(&zram->init_lock);

return sz;
}

+static void comp_algorithm_set(struct zram *zram, u32 idx, const char *alg)
+{
+ /* Do not kfree() algs that we didn't allocate, IOW the default ones */
+ if (zram->comp_algs[idx] != default_compressor)
+ kfree(zram->comp_algs[idx]);
+ zram->comp_algs[idx] = 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;

- strlcpy(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_ZCOMP, compressor);
up_write(&zram->init_lock);
return len;
}
@@ -1292,7 +1309,7 @@ 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_ZCOMP]);

src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
if (size == PAGE_SIZE) {
@@ -1304,7 +1321,7 @@ 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_ZCOMP]);
}
zs_unmap_object(zram->mem_pool, handle);
zram_slot_unlock(zram, index);
@@ -1371,13 +1388,13 @@ 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_ZCOMP]);
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_ZCOMP]);
pr_err("Compression failed! err=%d\n", ret);
zs_free(zram->mem_pool, handle);
return ret;
@@ -1405,7 +1422,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
__GFP_HIGHMEM |
__GFP_MOVABLE);
if (IS_ERR((void *)handle)) {
- zcomp_stream_put(zram->comp);
+ zcomp_stream_put(zram->comps[ZRAM_PRIMARY_ZCOMP]);
atomic64_inc(&zram->stats.writestall);
handle = zs_malloc(zram->mem_pool, comp_len,
GFP_NOIO | __GFP_HIGHMEM |
@@ -1422,14 +1439,14 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
* 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_ZCOMP]);
}

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_ZCOMP]);
zs_free(zram->mem_pool, handle);
return -ENOMEM;
}
@@ -1443,7 +1460,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
if (comp_len == PAGE_SIZE)
kunmap_atomic(src);

- zcomp_stream_put(zram->comp);
+ zcomp_stream_put(zram->comps[ZRAM_PRIMARY_ZCOMP]);
zs_unmap_object(zram->mem_pool, handle);
atomic64_add(comp_len, &zram->stats.compr_data_size);
out:
@@ -1718,6 +1735,20 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
return ret;
}

+static void zram_destroy_comps(struct zram *zram)
+{
+ u32 idx;
+
+ for (idx = 0; idx < ZRAM_MAX_ZCOMPS; idx++) {
+ struct zcomp *comp = zram->comps[idx];
+
+ zram->comps[idx] = NULL;
+ if (IS_ERR_OR_NULL(comp))
+ continue;
+ zcomp_destroy(comp);
+ }
+}
+
static void zram_reset_device(struct zram *zram)
{
down_write(&zram->init_lock);
@@ -1735,11 +1766,11 @@ 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_ZCOMP, default_compressor);
up_write(&zram->init_lock);
}

@@ -1750,6 +1781,7 @@ static ssize_t disksize_store(struct device *dev,
struct zcomp *comp;
struct zram *zram = dev_to_zram(dev);
int err;
+ u32 idx;

disksize = memparse(buf, NULL);
if (!disksize)
@@ -1768,22 +1800,25 @@ 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 (idx = 0; idx < ZRAM_MAX_ZCOMPS; idx++) {
+ comp = zcomp_create(zram->comp_algs[idx]);
+ if (IS_ERR(comp)) {
+ pr_err("Cannot initialise %s compressing backend\n",
+ zram->comp_algs[idx]);
+ err = PTR_ERR(comp);
+ goto out_free_comps;
+ }

- zram->comp = comp;
+ zram->comps[idx] = 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);
@@ -1979,7 +2014,7 @@ static int zram_add(void)
if (ret)
goto out_cleanup_disk;

- strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
+ zram->comp_algs[ZRAM_PRIMARY_ZCOMP] = 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 80c3b43b4828..af3d6f6bfcff 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -90,10 +90,20 @@ struct zram_stats {
#endif
};

+#ifdef CONFIG_ZRAM_MULTI_COMP
+#define ZRAM_PRIMARY_ZCOMP 0
+#define ZRAM_SECONDARY_ZCOMP 1
+#define ZRAM_MAX_ZCOMPS 2
+#else
+#define ZRAM_PRIMARY_ZCOMP 0
+#define ZRAM_SECONDARY_ZCOMP 0
+#define ZRAM_MAX_ZCOMPS 1
+#endif
+
struct zram {
struct zram_table_entry *table;
struct zs_pool *mem_pool;
- struct zcomp *comp;
+ struct zcomp *comps[ZRAM_MAX_ZCOMPS];
struct gendisk *disk;
/* Prevent concurrent execution of device init */
struct rw_semaphore init_lock;
@@ -108,7 +118,7 @@ struct zram {
* we can store in a disk.
*/
u64 disksize; /* bytes */
- char compressor[CRYPTO_MAX_ALG_NAME];
+ const char *comp_algs[ZRAM_MAX_ZCOMPS];
/*
* zram is claimed so open request will be failed
*/
--
2.37.2.789.g6183377224-goog

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