linux-kernel - Re: [PATCHv4 2/9] zram: Add recompression algorithm sysfs knob

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Date:   Thu, 3 Nov 2022 14:36:15 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCHv4 2/9] zram: Add recompression algorithm sysfs knob

On (22/11/03 13:09), Sergey Senozhatsky wrote:
> On (22/11/03 12:05), Sergey Senozhatsky wrote:
> > What is the use case for removal of a secondary algorithm?
> > 
> > > My point is that we don't need to implement it atm but makes the
> > > interface to open the possibility for future extension.
> > > 
> > > What do you think?
> > 
> > So, as far as I understand, we don't have reason to add remove_recomp_algo
> > right now. And existing recomp_algo does not enforce any particular format,
> > it can be extended. Right now we accept "$name" but can do something like
> > "$name:$priority".
> 
> Or with keywords:
> 
> 	name=STRING priority=INT
> 
> and the only legal priority for now is 1.


E.g. recomp_algorithm support for algorithms name= and optional
integer priority=.

I sort of like the recomp_algorithm name so far, but we can change it.

---

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index cf9d3474b80c..9a614253de07 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1102,9 +1102,38 @@ static ssize_t recomp_algorithm_store(struct device *dev,
 				      size_t len)
 {
 	struct zram *zram = dev_to_zram(dev);
+	int prio = ZRAM_SECONDARY_ZCOMP;
+	char *args, *param, *val;
+	char *alg = NULL;
 	int ret;
 
-	ret = __comp_algorithm_store(zram, ZRAM_SECONDARY_ZCOMP, buf);
+	args = skip_spaces(buf);
+	while (*args) {
+		args = next_arg(args, &param, &val);
+
+		if (!*val)
+			return -EINVAL;
+
+		if (!strcmp(param, "name")) {
+			alg = val;
+			continue;
+		}
+
+		if (!strcmp(param, "priority")) {
+			ret = kstrtoint(val, 10, &prio);
+			if (ret)
+				return ret;
+			continue;
+		}
+	}
+
+	if (!alg)
+		return -EINVAL;
+
+	if (prio < ZRAM_SECONDARY_ZCOMP || prio >= ZRAM_MAX_ZCOMPS)
+		return -EINVAL;
+
+	ret = __comp_algorithm_store(zram, prio, alg);
 	return ret ? ret : len;
 }
 #endif