Commit e74a1c6a authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Jens Axboe
Browse files

zram: pass buffer offset to zcomp_available_show() 



In most cases zcomp_available_show() is the only emitting
function that is called from sysfs read() handler, so it
assumes that there is a whole PAGE_SIZE buffer to work with.
There is an exception, however: recomp_algorithm_show().

In recomp_algorithm_show() we prepend the buffer with
priority number before we pass it to zcomp_available_show(),
so it cannot assume PAGE_SIZE anymore and must take
recomp_algorithm_show() modifications into consideration.
Therefore we need to pass buffer offset to zcomp_available_show().

Also convert it to use sysfs_emit_at(), to stay aligned
with the rest of zram's sysfs read() handlers.

On practice we are never even close to using the whole PAGE_SIZE
buffer, so that's not a critical bug, but still.

Signed-off-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Link: https://lore.kernel.org/r/20250627071840.1394242-1-senozhatsky@chromium.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 264a3fda

drivers/block/zram/zcomp.c

+7 −8
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#include <linux/sched.h>

#include <linux/cpuhotplug.h>

#include <linux/vmalloc.h>

#include <linux/sysfs.h>



#include "zcomp.h"
@@ -89,23 +90,21 @@ bool zcomp_available_algorithm(const char *comp) 
}



/* show available compressors */

ssize_t zcomp_available_show(const char *comp, char *buf)

ssize_t zcomp_available_show(const char *comp, char *buf, ssize_t at)

{

	ssize_t sz = 0;

	int i;



	for (i = 0; i < ARRAY_SIZE(backends) - 1; i++) {

		if (!strcmp(comp, backends[i]->name)) {

			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,

					"[%s] ", backends[i]->name);

			at += sysfs_emit_at(buf, at, "[%s] ",

					    backends[i]->name);

		} else {

			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,

					"%s ", backends[i]->name);

			at += sysfs_emit_at(buf, at, "%s ", backends[i]->name);

		}

	}



	sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");

	return sz;

	at += sysfs_emit_at(buf, at, "\n");

	return at;

}



struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)

drivers/block/zram/zcomp.h

+1 −1
Original line number Diff line number Diff line
@@ -79,7 +79,7 @@ struct zcomp { 


int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node);

int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node);

ssize_t zcomp_available_show(const char *comp, char *buf);

ssize_t zcomp_available_show(const char *comp, char *buf, ssize_t at);

bool zcomp_available_algorithm(const char *comp);



struct zcomp *zcomp_create(const char *alg, struct zcomp_params *params);

drivers/block/zram/zram_drv.c

+5 −4
Original line number Diff line number Diff line
@@ -1225,12 +1225,13 @@ static void comp_algorithm_set(struct zram *zram, u32 prio, const char *alg) 
	zram->comp_algs[prio] = alg;

}



static ssize_t __comp_algorithm_show(struct zram *zram, u32 prio, char *buf)

static ssize_t __comp_algorithm_show(struct zram *zram, u32 prio,

				     char *buf, ssize_t at)

{

	ssize_t sz;



	down_read(&zram->init_lock);

	sz = zcomp_available_show(zram->comp_algs[prio], buf);

	sz = zcomp_available_show(zram->comp_algs[prio], buf, at);

	up_read(&zram->init_lock);



	return sz;
@@ -1387,7 +1388,7 @@ static ssize_t comp_algorithm_show(struct device *dev, 
{

	struct zram *zram = dev_to_zram(dev);



	return __comp_algorithm_show(zram, ZRAM_PRIMARY_COMP, buf);

	return __comp_algorithm_show(zram, ZRAM_PRIMARY_COMP, buf, 0);

}



static ssize_t comp_algorithm_store(struct device *dev,
@@ -1416,7 +1417,7 @@ static ssize_t recomp_algorithm_show(struct device *dev, 
			continue;



		sz += sysfs_emit_at(buf, sz, "#%d: ", prio);

		sz += __comp_algorithm_show(zram, prio, buf + sz);

		sz += __comp_algorithm_show(zram, prio, buf, sz);

	}



	return sz;