zram-use-statically-allocated-compression-algorithm-names.patch removed from -mm tree

merged mm-stable Andrew Morton 1 participant 1 message Mar 24

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2026-03-24 21:43 UTC #0 lore raw

The quilt patch titled
Subject: zram: use statically allocated compression algorithm names
has been removed from the -mm tree. Its filename was
zram-use-statically-allocated-compression-algorithm-names.patch

This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: gao xu <[email protected]>
Subject: zram: use statically allocated compression algorithm names
Date: Thu, 26 Feb 2026 12:37:22 +0000

Currently, zram dynamically allocates memory for compressor algorithm names when they are set by the user. This requires careful memory management, including explicit kfree calls and special handling to avoid freeing statically defined default compressor names.

This patch refactors the way zram handles compression algorithm names. Instead of storing dynamically allocated copies, zram->comp_algs will now store pointers directly to the static name strings defined within the zcomp_ops backend structures, thereby removing the need for conditional kfree calls.

Link https://lkml.kernel.org/r/[email protected] open here

Signed-off-by gao xu <[email protected]>

Reviewed-by Sergey Senozhatsky <[email protected]>

Cc Jens Axboe <[email protected]>

Cc Minchan Kim <[email protected]>

Cc Suren Baghdasaryan <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

---

 drivers/block/zram/zcomp.c    |    9 +++++++--
 drivers/block/zram/zcomp.h    |    2 +-
 drivers/block/zram/zram_drv.c |   28 +++++-----------------------
 3 files changed, 13 insertions(+), 26 deletions(-)

drivers/block/zram/zcomp.c renamed from drivers/block/zram/zcomp.c~zram-use-statically-allocated-compression-algorithm-names +7 -2

@@ -84,9 +84,14 @@ static const struct zcomp_ops *lookup_ba
 	return backends[i];
 }
 
-bool zcomp_available_algorithm(const char *comp)
+const char *zcomp_lookup_backend_name(const char *comp)
 {
-	return lookup_backend_ops(comp) != NULL;
+	const struct zcomp_ops *backend = lookup_backend_ops(comp);
+
+	if (backend)
+		return backend->name;
+
+	return NULL;
 }
 
 /* show available compressors */

drivers/block/zram/zcomp.h renamed from drivers/block/zram/zcomp.h~zram-use-statically-allocated-compression-algorithm-names +1 -1

@@ -80,7 +80,7 @@ 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 at);
-bool zcomp_available_algorithm(const char *comp);
+const char *zcomp_lookup_backend_name(const char *comp);
 
 struct zcomp *zcomp_create(const char *alg, struct zcomp_params *params);
 void zcomp_destroy(struct zcomp *comp);

drivers/block/zram/zram_drv.c renamed from drivers/block/zram/zram_drv.c~zram-use-statically-allocated-compression-algorithm-names +5 ~~-23~~

@@ -1621,43 +1621,29 @@ static void zram_debugfs_unregister(stru
 
 static void comp_algorithm_set(struct zram *zram, u32 prio, const char *alg)
 {
-	/* Do not free statically defined compression algorithms */
-	if (zram->comp_algs[prio] != default_compressor)
-		kfree(zram->comp_algs[prio]);
-
 	zram->comp_algs[prio] = alg;
 }
 
 static int __comp_algorithm_store(struct zram *zram, u32 prio, const char *buf)
 {
-	char *compressor;
+	const char *alg;
 	size_t sz;
 
 	sz = strlen(buf);
 	if (sz >= ZRAM_MAX_ALGO_NAME_SZ)
 		return -E2BIG;
 
-	compressor = kstrdup(buf, GFP_KERNEL);
-	if (!compressor)
-		return -ENOMEM;
-
-	/* ignore trailing newline */
-	if (sz > 0 && compressor[sz - 1] == '\n')
-		compressor[sz - 1] = 0x00;
-
-	if (!zcomp_available_algorithm(compressor)) {
-		kfree(compressor);
+	alg = zcomp_lookup_backend_name(buf);
+	if (!alg)
 		return -EINVAL;
-	}
 
 	guard(rwsem_write)(&zram->dev_lock);
 	if (init_done(zram)) {
-		kfree(compressor);
 		pr_info("Can't change algorithm for initialized device\n");
 		return -EBUSY;
 	}
 
-	comp_algorithm_set(zram, prio, compressor);
+	comp_algorithm_set(zram, prio, alg);
 	return 0;
 }

@@ -2840,12 +2826,8 @@ static void zram_destroy_comps(struct zr
 		zram->num_active_comps--;
 	}
 
-	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
-		/* Do not free statically defined compression algorithms */
-		if (zram->comp_algs[prio] != default_compressor)
-			kfree(zram->comp_algs[prio]);
+	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++)
 		zram->comp_algs[prio] = NULL;
-	}
 
 	zram_comp_params_reset(zram);
 }

Patches currently in -mm which might be from [email protected] are

zram-optimize-lz4-dictionary-compression-performance-v2.patch