There's nothing special about zram and lzo. It works just fine without it, so
as long as at least one of the other supported compression algorithms is
selected.
Suggested-by: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Signed-off-by: Rui Salvaterra <rsalvaterra@xxxxxxxxx>
---
v4: incorporate Sergey's feedback and fix a small typo.
v3: fix the default selection when lzo isn't present. Rebase against 5.10-rc1.
v2: fix the dependency on CRYPTO.
drivers/block/zram/Kconfig | 6 +++++-
drivers/block/zram/zcomp.c | 17 +++++++++++++++++
drivers/block/zram/zcomp.h | 1 +
drivers/block/zram/zram_drv.c | 5 +++--
4 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index fe7a4b7d30cf..141ce0ebad06 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -2,7 +2,6 @@
config ZRAM
tristate "Compressed RAM block device support"
depends on BLOCK && SYSFS && ZSMALLOC && CRYPTO
- select CRYPTO_LZO
help
Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
Pages written to these disks are compressed and stored in memory
@@ -14,6 +13,11 @@ config ZRAM
See Documentation/admin-guide/blockdev/zram.rst for more information.
+config ZRAM_AUTOSEL_ALGO
+ def_bool y
+ depends on ZRAM && !(CRYPTO_LZ4 || CRYPTO_LZ4HC || CRYPTO_842 || CRYPTO_ZSTD)
+ select CRYPTO_LZO
+
config ZRAM_WRITEBACK
bool "Write back incompressible or idle page to backing device"
depends on ZRAM
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 33e3b76c4fa9..4fad177c78c4 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -15,8 +15,10 @@
#include "zcomp.h"
static const char * const backends[] = {
+#if IS_ENABLED(CONFIG_CRYPTO_LZO)
"lzo",
"lzo-rle",
+#endif
#if IS_ENABLED(CONFIG_CRYPTO_LZ4)
"lz4",
#endif
@@ -202,6 +204,21 @@ void zcomp_destroy(struct zcomp *comp)
kfree(comp);
}
+const char *default_compressor(void)
+{
+ /*
+ * Pick the first available one (there should be at least one).
+ *
+ * In theory, we can drop all the ifdefs from backends[] and
+ * just iterate backends array doing crypto_has_comp(comp, 0, 0)
+ * for each entry and return the first one which is recognized by
+ * crypto. But crypto_has_comp() modprobes compression drivers,
+ * so we may end up with extra loaded drivers, when the 'default'
+ * compressor is not what zram is configured to use.
+ */
+ return backends[0];
+}
+
/*
* search available compressors for requested algorithm.
* allocate new zcomp and initialize it. return compressing
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index 40f6420f4b2e..f104be9eae9c 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -27,6 +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);
+const char *default_compressor(void);
struct zcomp *zcomp_create(const char *comp);
void zcomp_destroy(struct zcomp *comp);
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 1b697208d661..f02ee050c7bf 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -42,7 +42,6 @@ static DEFINE_IDR(zram_index_idr);
static DEFINE_MUTEX(zram_index_mutex);
static int zram_major;
-static const char *default_compressor = "lzo-rle";
/* Module params (documentation at end) */
static unsigned int num_devices = 1;
@@ -1960,7 +1959,9 @@ static int zram_add(void)
blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, zram->disk->queue);
device_add_disk(NULL, zram->disk, zram_disk_attr_groups);
- strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
+ strlcpy(zram->compressor,
+ default_compressor(),
+ sizeof(zram->compressor));
zram_debugfs_register(zram);
pr_info("Added device: %s\n", zram->disk->disk_name);
--
2.29.1
