zram: factor out single stream compression
This is preparation patch to add multi stream support to zcomp. Introduce struct zcomp_strm_single and a set of functions to manage zcomp_strm stream access. zcomp_strm_single implements single compession stream, same way as current zcomp implementation. This moves zcomp_strm stream control and locking from zcomp, so compressing backend zcomp is not aware of required locking. Single and multi streams require different locking schemes. Minchan Kim reported that spinlock-based locking scheme (which is used in multi stream implementation) has demonstrated a severe perfomance regression for single compression stream case, comparing to mutex-based. see https://lkml.org/lkml/2014/2/18/16 The following set of functions added: - zcomp_strm_single_find()/zcomp_strm_single_release() find and release a compression stream, implement required locking - zcomp_strm_single_create()/zcomp_strm_single_destroy() create and destroy zcomp_strm_single New ->strm_find() and ->strm_release() callbacks added to zcomp, which are set to zcomp_strm_single_find() and zcomp_strm_single_release() during initialisation. Instead of direct locking and zcomp_strm access from zcomp_strm_find() and zcomp_strm_release(), zcomp now calls ->strm_find() and ->strm_release() correspondingly. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -16,6 +16,14 @@
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#include "zcomp.h"
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#include "zcomp_lzo.h"
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/*
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* single zcomp_strm backend
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*/
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struct zcomp_strm_single {
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struct mutex strm_lock;
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struct zcomp_strm *zstrm;
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};
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static struct zcomp_backend *find_backend(const char *compress)
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{
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if (strncmp(compress, "lzo", 3) == 0)
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@ -54,15 +62,56 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
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return zstrm;
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}
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static struct zcomp_strm *zcomp_strm_single_find(struct zcomp *comp)
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{
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struct zcomp_strm_single *zs = comp->stream;
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mutex_lock(&zs->strm_lock);
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return zs->zstrm;
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}
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static void zcomp_strm_single_release(struct zcomp *comp,
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struct zcomp_strm *zstrm)
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{
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struct zcomp_strm_single *zs = comp->stream;
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mutex_unlock(&zs->strm_lock);
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}
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static void zcomp_strm_single_destroy(struct zcomp *comp)
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{
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struct zcomp_strm_single *zs = comp->stream;
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zcomp_strm_free(comp, zs->zstrm);
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kfree(zs);
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}
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static int zcomp_strm_single_create(struct zcomp *comp)
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{
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struct zcomp_strm_single *zs;
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comp->destroy = zcomp_strm_single_destroy;
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comp->strm_find = zcomp_strm_single_find;
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comp->strm_release = zcomp_strm_single_release;
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zs = kmalloc(sizeof(struct zcomp_strm_single), GFP_KERNEL);
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if (!zs)
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return -ENOMEM;
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comp->stream = zs;
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mutex_init(&zs->strm_lock);
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zs->zstrm = zcomp_strm_alloc(comp);
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if (!zs->zstrm) {
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kfree(zs);
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return -ENOMEM;
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}
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return 0;
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}
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struct zcomp_strm *zcomp_strm_find(struct zcomp *comp)
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{
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mutex_lock(&comp->strm_lock);
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return comp->zstrm;
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return comp->strm_find(comp);
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}
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void zcomp_strm_release(struct zcomp *comp, struct zcomp_strm *zstrm)
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{
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mutex_unlock(&comp->strm_lock);
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comp->strm_release(comp, zstrm);
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}
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int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
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@ -80,7 +129,7 @@ int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
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void zcomp_destroy(struct zcomp *comp)
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{
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zcomp_strm_free(comp, comp->zstrm);
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comp->destroy(comp);
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kfree(comp);
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}
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@ -104,10 +153,7 @@ struct zcomp *zcomp_create(const char *compress)
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return NULL;
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comp->backend = backend;
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mutex_init(&comp->strm_lock);
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comp->zstrm = zcomp_strm_alloc(comp);
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if (!comp->zstrm) {
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if (zcomp_strm_single_create(comp) != 0) {
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kfree(comp);
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return NULL;
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}
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@ -39,9 +39,12 @@ struct zcomp_backend {
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/* dynamic per-device compression frontend */
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struct zcomp {
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struct mutex strm_lock;
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struct zcomp_strm *zstrm;
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void *stream;
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struct zcomp_backend *backend;
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struct zcomp_strm *(*strm_find)(struct zcomp *comp);
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void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);
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void (*destroy)(struct zcomp *comp);
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};
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struct zcomp *zcomp_create(const char *comp);
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