On Sat, Jun 04, 2016 at 11:48:58AM +0900, Sergey Senozhatsky wrote: > 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). > > Signed-off-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com> Acked-by: Minchan Kim <minc...@kernel.org>
