Commit 60a726e3 authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
Browse files

zram: propagate error to user 



When we initialized zcomp with single, we couldn't change
max_comp_streams without zram reset but current interface doesn't show
any error to user and even it changes max_comp_streams's value without
any effect so it would make user very confusing.

This patch prevents max_comp_streams's change when zcomp was initialized
as single zcomp and emit the error to user(ex, echo).

[akpm@linux-foundation.org: don't return with the lock held, per Sergey]
[fengguang.wu@intel.com: fix coccinelle warnings]
Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Acked-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fcfa8d95

Documentation/blockdev/zram.txt

+5 −4
Original line number Diff line number Diff line
@@ -37,10 +37,11 @@ Note: 
In order to enable compression backend's multi stream support max_comp_streams

must be initially set to desired concurrency level before ZRAM device

initialisation. Once the device initialised as a single stream compression

backend (max_comp_streams equals to 0) changing the value of max_comp_streams

will not take any effect, because single stream compression backend implemented

as a special case and does not support dynamic max_comp_streams. Only multi

stream backend supports dynamic max_comp_streams adjustment.

backend (max_comp_streams equals to 1), you will see error if you try to change

the value of max_comp_streams because single stream compression backend

implemented as a special case by lock overhead issue and does not support

dynamic max_comp_streams. Only multi stream backend supports dynamic

max_comp_streams adjustment.



3) Select compression algorithm

	Using comp_algorithm device attribute one can see available and

drivers/block/zram/zcomp.c

+5 −5
Original line number Diff line number Diff line
@@ -153,7 +153,7 @@ static void zcomp_strm_multi_release(struct zcomp *comp, struct zcomp_strm *zstr 
}



/* change max_strm limit */

static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int num_strm)

static bool zcomp_strm_multi_set_max_streams(struct zcomp *comp, int num_strm)

{

	struct zcomp_strm_multi *zs = comp->stream;

	struct zcomp_strm *zstrm;
@@ -172,7 +172,7 @@ static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int num_strm) 
		zs->avail_strm--;

	}

	spin_unlock(&zs->strm_lock);

	return 0;

	return true;

}



static void zcomp_strm_multi_destroy(struct zcomp *comp)
@@ -232,10 +232,10 @@ static void zcomp_strm_single_release(struct zcomp *comp, 
	mutex_unlock(&zs->strm_lock);

}



static int zcomp_strm_single_set_max_streams(struct zcomp *comp, int num_strm)

static bool zcomp_strm_single_set_max_streams(struct zcomp *comp, int num_strm)

{

	/* zcomp_strm_single support only max_comp_streams == 1 */

	return -ENOTSUPP;

	return false;

}



static void zcomp_strm_single_destroy(struct zcomp *comp)
@@ -284,7 +284,7 @@ ssize_t zcomp_available_show(const char *comp, char *buf) 
	return sz;

}



int zcomp_set_max_streams(struct zcomp *comp, int num_strm)

bool zcomp_set_max_streams(struct zcomp *comp, int num_strm)

{

	return comp->set_max_streams(comp, num_strm);

}

drivers/block/zram/zcomp.h

+2 −2
Original line number Diff line number Diff line
@@ -46,7 +46,7 @@ struct zcomp { 


	struct zcomp_strm *(*strm_find)(struct zcomp *comp);

	void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);

	int (*set_max_streams)(struct zcomp *comp, int num_strm);

	bool (*set_max_streams)(struct zcomp *comp, int num_strm);

	void (*destroy)(struct zcomp *comp);

};
@@ -64,5 +64,5 @@ int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm, 
int zcomp_decompress(struct zcomp *comp, const unsigned char *src,

		size_t src_len, unsigned char *dst);



int zcomp_set_max_streams(struct zcomp *comp, int num_strm);

bool zcomp_set_max_streams(struct zcomp *comp, int num_strm);

#endif /* _ZCOMP_H_ */

drivers/block/zram/zram_drv.c

+13 −4
Original line number Diff line number Diff line
@@ -127,19 +127,28 @@ static ssize_t max_comp_streams_store(struct device *dev, 
{

	int num;

	struct zram *zram = dev_to_zram(dev);

	int ret;



	if (kstrtoint(buf, 0, &num))

		return -EINVAL;

	ret = kstrtoint(buf, 0, &num);

	if (ret < 0)

		return ret;

	if (num < 1)

		return -EINVAL;



	down_write(&zram->init_lock);

	if (init_done(zram)) {

		if (zcomp_set_max_streams(zram->comp, num))

		if (!zcomp_set_max_streams(zram->comp, num)) {

			pr_info("Cannot change max compression streams\n");

			ret = -EINVAL;

			goto out;

		}

	}



	zram->max_comp_streams = num;

	ret = len;

out:

	up_write(&zram->init_lock);

	return len;

	return ret;

}



static ssize_t comp_algorithm_show(struct device *dev,

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