From 415403be37e204632b17bdb6857890fe5a220cea Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Tue, 26 Jul 2016 15:22:48 -0700 Subject: [PATCH] zram: use crypto api to check alg availability There is no way to get a string with all the crypto comp algorithms supported by the crypto comp engine, so we need to maintain our own backends list. At the same time we additionally need to use crypto_has_comp() to make sure that the user has requested a compression algorithm that is recognized by the crypto comp engine. Relying on /proc/crypto is not an options here, because it does not show not-yet-inserted compression modules. Example: modprobe zram cat /proc/crypto | grep -i lz4 modprobe lz4 cat /proc/crypto | grep -i lz4 name : lz4 driver : lz4-generic module : lz4 So the user can't tell exactly if the lz4 is really supported from /proc/crypto output, unless someone or something has loaded it. This patch also adds crypto_has_comp() to zcomp_available_show(). We store all the compression algorithms names in zcomp's `backends' array, regardless the CONFIG_CRYPTO_FOO configuration, but show only those that are also supported by crypto engine. This helps user to know the exact list of compression algorithms that can be used. Example: module lz4 is not loaded yet, but is supported by the crypto engine. /proc/crypto has no information on this module, while zram's `comp_algorithm' lists it: cat /proc/crypto | grep -i lz4 cat /sys/block/zram0/comp_algorithm [lzo] lz4 deflate lz4hc 842 We still use the `backends' array to determine if the requested compression backend is known to crypto api. This array, however, may not contain some entries, therefore as the last step we call crypto_has_comp() function which attempts to insmod the requested compression algorithm to determine if crypto api supports it. The advantage of this method is that now we permit the usage of out-of-tree crypto compression modules (implementing S/W or H/W compression). [sergey.senozhatsky@gmail.com: zram-use-crypto-api-to-check-alg-availability-v3] Link: http://lkml.kernel.org/r/20160604024902.11778-4-sergey.senozhatsky@gmail.com Link: http://lkml.kernel.org/r/20160531122017.2878-5-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky Acked-by: Minchan Kim Cc: Joonsoo Kim Signed-off-by: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/blockdev/zram.txt | 11 ++++++ drivers/block/zram/zcomp.c | 61 ++++++++++++++++++++------------- drivers/block/zram/zram_drv.c | 16 +++++---- drivers/block/zram/zram_drv.h | 5 +-- 4 files changed, 60 insertions(+), 33 deletions(-) diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 13100fb3c26d..7c05357360a7 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -83,6 +83,17 @@ pre-created. Default: 1. #select lzo compression algorithm echo lzo > /sys/block/zram0/comp_algorithm + For the time being, the `comp_algorithm' content does not necessarily + show every compression algorithm supported by the kernel. We keep this + list primarily to simplify device configuration and one can configure + a new device with a compression algorithm that is not listed in + `comp_algorithm'. The thing is that, internally, ZRAM uses Crypto API + and, if some of the algorithms were built as modules, it's impossible + to list all of them using, for instance, /proc/crypto or any other + method. This, however, has an advantage of permitting the usage of + custom crypto compression modules (implementing S/W or H/W + compression). + 4) Set Disksize Set disk size by writing the value to sysfs node 'disksize'. The value can be either in bytes or you can use mem suffixes. diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index f35726860a1b..a2b4eb85b41d 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -26,17 +26,6 @@ static const char * const backends[] = { NULL }; -static const char *find_backend(const char *compress) -{ - int i = 0; - while (backends[i]) { - if (sysfs_streq(compress, backends[i])) - break; - i++; - } - return backends[i]; -} - static void zcomp_strm_free(struct zcomp_strm *zstrm) { if (!IS_ERR_OR_NULL(zstrm->tfm)) @@ -68,30 +57,56 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp, gfp_t flags) return zstrm; } +bool zcomp_available_algorithm(const char *comp) +{ + int i = 0; + + while (backends[i]) { + if (sysfs_streq(comp, backends[i])) + return true; + i++; + } + + /* + * Crypto does not ignore a trailing new line symbol, + * so make sure you don't supply a string containing + * one. + * This also means that we permit zcomp initialisation + * with any compressing algorithm known to crypto api. + */ + return crypto_has_comp(comp, 0, 0) == 1; +} + /* show available compressors */ ssize_t zcomp_available_show(const char *comp, char *buf) { + bool known_algorithm = false; ssize_t sz = 0; int i = 0; - while (backends[i]) { - if (!strcmp(comp, backends[i])) + for (; backends[i]; i++) { + if (!strcmp(comp, backends[i])) { + known_algorithm = true; sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2, "[%s] ", backends[i]); - else + } else { sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2, "%s ", backends[i]); - i++; + } } + + /* + * Out-of-tree module known to crypto api or a missing + * entry in `backends'. + */ + if (!known_algorithm && crypto_has_comp(comp, 0, 0) == 1) + sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2, + "[%s] ", comp); + sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n"); return sz; } -bool zcomp_available_algorithm(const char *comp) -{ - return find_backend(comp) != NULL; -} - struct zcomp_strm *zcomp_stream_get(struct zcomp *comp) { return *get_cpu_ptr(comp->stream); @@ -227,18 +242,16 @@ void zcomp_destroy(struct zcomp *comp) struct zcomp *zcomp_create(const char *compress) { struct zcomp *comp; - const char *backend; int error; - backend = find_backend(compress); - if (!backend) + if (!zcomp_available_algorithm(compress)) return ERR_PTR(-EINVAL); comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL); if (!comp) return ERR_PTR(-ENOMEM); - comp->name = backend; + comp->name = compress; error = zcomp_init(comp); if (error) { kfree(comp); diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 65d140336289..c2a1d7dbaec9 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -342,9 +342,16 @@ 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[CRYPTO_MAX_ALG_NAME]; size_t sz; - if (!zcomp_available_algorithm(buf)) + strlcpy(compressor, buf, sizeof(compressor)); + /* ignore trailing newline */ + sz = strlen(compressor); + if (sz > 0 && compressor[sz - 1] == '\n') + compressor[sz - 1] = 0x00; + + if (!zcomp_available_algorithm(compressor)) return -EINVAL; down_write(&zram->init_lock); @@ -353,13 +360,8 @@ static ssize_t comp_algorithm_store(struct device *dev, pr_info("Can't change algorithm for initialized device\n"); return -EBUSY; } - strlcpy(zram->compressor, buf, sizeof(zram->compressor)); - - /* ignore trailing newline */ - sz = strlen(zram->compressor); - if (sz > 0 && zram->compressor[sz - 1] == '\n') - zram->compressor[sz - 1] = 0x00; + strlcpy(zram->compressor, compressor, sizeof(compressor)); up_write(&zram->init_lock); return len; } diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index 3f5bf66a27e4..74fcf10da374 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -15,8 +15,9 @@ #ifndef _ZRAM_DRV_H_ #define _ZRAM_DRV_H_ -#include +#include #include +#include #include "zcomp.h" @@ -113,7 +114,7 @@ struct zram { * we can store in a disk. */ u64 disksize; /* bytes */ - char compressor[10]; + char compressor[CRYPTO_MAX_ALG_NAME]; /* * zram is claimed so open request will be failed */ -- 2.20.1