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Date: Thu, 13 Feb 2014 20:52:51 +0300
From: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To: Minchan Kim <minchan@...nel.org>
Cc: Jerome Marchand <jmarchan@...hat.com>,
Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 1/4] zram: introduce compressing backend abstraction
Hello Minchan,
thank you for review.
On (02/13/14 13:53), Minchan Kim wrote:
>
> Hello Sergey,
>
[..]
> > + struct zcomp_strm, list);
> > + list_del(&zstrm->list);
> > + spin_unlock(&comp->buffer_lock);
> > + return zstrm;
> > +}
> > +
> > +/* add zcomp_strm back to idle list and wake up waiter (if any) */
> > +void zcomp_strm_put(struct zcomp *comp, struct zcomp_strm *zstrm)
> > +{
> > + spin_lock(&comp->buffer_lock);
> > + list_add_tail(&zstrm->list, &comp->idle_strm);
>
> What I said "queue" in previous review is that I thougt stack might
> be more cache-freindly than queue so list_add is proper than list_add_tail.
> But it seems you have a reason to list_add_tail. If so, could you explain
> what you expect?
sure, 100% my mistake. agreed, using the most recently used zstrm is the
right thing to do. I was not attentive, sorry.
> > + spin_unlock(&comp->buffer_lock);
> > +
> > + wake_up(&comp->strm_wait);
> > +}
> > +
> > +int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
> > + const unsigned char *src, size_t src_len, size_t *dst_len)
> > +{
> > + return comp->backend->compress(src, src_len, zstrm->buffer,
> > + dst_len, zstrm->private);
> > +}
>
> We need src_len? it's always PAGE_SIZE.
>
> > +
> > +int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
> > + size_t src_len, unsigned char *dst, size_t *dst_len)
> > +{
> > + return comp->backend->decompress(src, src_len, dst, dst_len);
>
> We need dst_len? It's always PAGE_SIZE, too.
>
the only reason why I left src_len is partial IO, where
`bv_len (src_len) != PAGE_SIZE'. no reason to keep dst_len.
I've addressed your concerns and notes from this email, emails
"zram: document max_comp_streams" and "zram: use zcomp compressing backends"
in PATCH v5.
thank you once again.
-ss
> > +}
> > +
> > +/* free allocated zcomp_strm buffers and zcomp */
> > +void zcomp_destroy(struct zcomp *comp)
> > +{
> > + struct zcomp_strm *zstrm;
> > + while (!list_empty(&comp->idle_strm)) {
> > + zstrm = list_entry(comp->idle_strm.next,
> > + struct zcomp_strm, list);
> > + list_del(&zstrm->list);
> > + zcomp_strm_free(comp, zstrm);
> > + }
> > + kfree(comp);
> > +}
> > +
> > +static struct zcomp_backend *find_backend(const char *compress)
> > +{
> > + if (sysfs_streq(compress, "lzo"))
> > + return &zcomp_lzo;
> > + return NULL;
> > +}
> > +
> > +/*
> > + * search available compressors for requested algorithm.
> > + * allocate new zcomp and initialize it. return NULL
> > + * if requested algorithm is not supported or in case
> > + * of init error
> > + */
> > +struct zcomp *zcomp_create(const char *compress)
> > +{
> > + struct zcomp *comp;
> > + struct zcomp_backend *backend;
> > + struct zcomp_strm *zstrm;
> > +
> > + backend = find_backend(compress);
> > + if (!backend)
> > + return NULL;
> > +
> > + comp = kmalloc(sizeof(struct zcomp), GFP_KERNEL);
> > + if (!comp)
> > + return NULL;
> > +
> > + comp->backend = backend;
> > + spin_lock_init(&comp->buffer_lock);
> > + INIT_LIST_HEAD(&comp->idle_strm);
> > + init_waitqueue_head(&comp->strm_wait);
> > +
> > + zstrm = zcomp_strm_alloc(comp);
> > + if (!zstrm) {
> > + zcomp_destroy(comp);
> > + return NULL;
> > + }
> > + list_add_tail(&zstrm->list, &comp->idle_strm);
>
> It's first adding to empty list so there is no difference
> between list_add and list_add_tail then, let's use list_add.
>
> > + return comp;
> > +}
> > diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
> > new file mode 100644
> > index 0000000..213e503
> > --- /dev/null
> > +++ b/drivers/block/zram/zcomp.h
> > @@ -0,0 +1,57 @@
> > +/*
> > + * Copyright (C) 2014 Sergey Senozhatsky.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version
> > + * 2 of the License, or (at your option) any later version.
> > + */
> > +
> > +#ifndef _ZCOMP_H_
> > +#define _ZCOMP_H_
> > +
> > +#include <linux/types.h>
> > +#include <linux/spinlock.h>
> > +
> > +struct zcomp_strm {
> > + void *buffer; /* compression/decompression buffer */
> > + void *private; /* algorithm workmem */
>
> Remove workmem.
>
> > + struct list_head list;
> > +};
> > +
> > +/* static compression backend */
> > +struct zcomp_backend {
> > + int (*compress)(const unsigned char *src, size_t src_len,
> > + unsigned char *dst, size_t *dst_len, void *wrkmem);
>
> Rename wrkmem.
>
> > +
> > + int (*decompress)(const unsigned char *src, size_t src_len,
> > + unsigned char *dst, size_t *dst_len);
> > +
> > + void * (*create)(void);
> > + void (*destroy)(void *private);
> > +
> > + const char *name;
> > +};
> > +
> > +/* dynamic per-device compression frontend */
> > +struct zcomp {
> > + /* protect strm list */
> > + spinlock_t buffer_lock;
>
> Pz, rename.
>
> > + /* list of available strms */
> > + struct list_head idle_strm;
> > + wait_queue_head_t strm_wait;
> > + struct zcomp_backend *backend;
> > +};
> > +
> > +struct zcomp *zcomp_create(const char *comp);
> > +void zcomp_destroy(struct zcomp *comp);
> > +
> > +struct zcomp_strm *zcomp_strm_get(struct zcomp *comp);
> > +void zcomp_strm_put(struct zcomp *comp, struct zcomp_strm *zsrtm);
> zstrm
> > +
> > +int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
> > + const unsigned char *src, size_t src_len, size_t *dst_len);
> > +
> > +int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
> > + size_t src_len, unsigned char *dst, size_t *dst_len);
> > +#endif /* _ZCOMP_H_ */
> > diff --git a/drivers/block/zram/zcomp_lzo.c b/drivers/block/zram/zcomp_lzo.c
> > new file mode 100644
> > index 0000000..2b23771
> > --- /dev/null
> > +++ b/drivers/block/zram/zcomp_lzo.c
> > @@ -0,0 +1,33 @@
> > +/*
> > + * Copyright (C) 2014 Sergey Senozhatsky.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version
> > + * 2 of the License, or (at your option) any later version.
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/slab.h>
> > +#include <linux/lzo.h>
> > +
> > +#include "zcomp.h"
> > +
> > +static void * lzo_create(void)
> > +{
> > + return kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> > +}
> > +
> > +static void lzo_destroy(void *private)
> > +{
> > + kfree(private);
> > +}
> > +
> > +extern struct zcomp_backend zcomp_lzo;
> > +struct zcomp_backend zcomp_lzo = {
> > + .compress = lzo1x_1_compress,
> > + .decompress = lzo1x_decompress_safe,
> > + .create = lzo_create,
> > + .destroy = lzo_destroy,
> > + .name = "lzo",
> > +};
> > --
> > 1.9.0.rc3.256.g4af3ebd
> >
> > --
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>
> --
> Kind regards,
> Minchan Kim
>
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