+ zram-use-statically-allocated-compression-algorithm-names.patch added to mm-new branch

+ zram-use-statically-allocated-compression-algorithm-names.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: zram: use statically allocated compression algorithm names
has been added to the -mm mm-new branch.  Its filename is
     zram-use-statically-allocated-compression-algorithm-names.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-use-statically-allocated-compression-algorithm-names.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: gao xu <gaoxu2@honor.com>
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/5bb2e9318d124dbcb2b743dcdce6a950@honor.com
Signed-off-by: gao xu <gaoxu2@honor.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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(-)

--- a/drivers/block/zram/zcomp.c~zram-use-statically-allocated-compression-algorithm-names
+++ a/drivers/block/zram/zcomp.c
@@ -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 */
--- a/drivers/block/zram/zcomp.h~zram-use-statically-allocated-compression-algorithm-names
+++ a/drivers/block/zram/zcomp.h
@@ -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);
--- a/drivers/block/zram/zram_drv.c~zram-use-statically-allocated-compression-algorithm-names
+++ a/drivers/block/zram/zram_drv.c
@@ -1637,43 +1637,29 @@ 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;
 }
 
@@ -2851,12 +2837,8 @@ 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 gaoxu2@honor.com are

zram-use-statically-allocated-compression-algorithm-names.patch

Re: + zram-use-statically-allocated-compression-algorithm-names.patch added to mm-new branch

[Sergey Senozhatsky]

On (26/02/26 08:45), Andrew Morton wrote:
> 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/5bb2e9318d124dbcb2b743dcdce6a950@honor.com
> Signed-off-by: gao xu <gaoxu2@honor.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>