public inbox for linux-mtd@lists.infradead.org
 help / color / mirror / Atom feed
From: Rosen Penev <rosenp@gmail.com>
To: linux-mtd@lists.infradead.org
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Kees Cook <kees@kernel.org>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	linux-kernel@vger.kernel.org (open list),
	linux-hardening@vger.kernel.org (open list:KERNEL HARDENING (not
	covered by other areas):Keyword:\b__counted_by(_le|_be)?\b)
Subject: [PATCH 2/2] mtd: concat: replace alloc + calloc with 1 alloc
Date: Wed,  4 Mar 2026 14:15:30 -0800	[thread overview]
Message-ID: <20260304221530.15018-3-rosenp@gmail.com> (raw)
In-Reply-To: <20260304221530.15018-1-rosenp@gmail.com>

A flex array can be used to reduce the allocation to 1.

And actually mtdconcat was using the pointer + 1 trick to point to the
overallocated area. Better alternatives exist.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/mtd/mtd_virt_concat.c | 10 ++--------
 drivers/mtd/mtdconcat.c       |  5 +----
 include/linux/mtd/concat.h    |  2 +-
 3 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/drivers/mtd/mtd_virt_concat.c b/drivers/mtd/mtd_virt_concat.c
index 89e223edac6a..b56f2431974b 100644
--- a/drivers/mtd/mtd_virt_concat.c
+++ b/drivers/mtd/mtd_virt_concat.c
@@ -32,7 +32,7 @@ struct mtd_virt_concat_node {
 	struct list_head head;
 	unsigned int count;
 	struct mtd_concat *concat;
-	struct device_node *nodes[] __counted_by(nodes);
+	struct device_node *nodes[] __counted_by(count);
 };
 
 /**
@@ -182,18 +182,12 @@ static int mtd_virt_concat_create_item(struct device_node *parts,
 	for (i = 1; i < count; i++)
 		item->nodes[i] = of_parse_phandle(parts, CONCAT_PROP, (i - 1));
 
-	concat = kzalloc(sizeof(*concat), GFP_KERNEL);
+	concat = kzalloc_flex(*concat, subdev, count, GFP_KERNEL);
 	if (!concat) {
 		kfree(item);
 		return -ENOMEM;
 	}
 
-	concat->subdev = kcalloc(count, sizeof(*concat->subdev), GFP_KERNEL);
-	if (!concat->subdev) {
-		kfree(item);
-		kfree(concat);
-		return -ENOMEM;
-	}
 	item->concat = concat;
 
 	list_add_tail(&item->head, &concat_node_list);
diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
index 241d15235d01..c97167d51fe2 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -627,7 +627,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
 				   const char *name)
 {				/* name for the new device   */
 	int i;
-	size_t size;
 	struct mtd_concat *concat;
 	struct mtd_info *subdev_master = NULL;
 	uint32_t max_erasesize, curr_erasesize;
@@ -640,15 +639,13 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
 	printk(KERN_NOTICE "into device \"%s\"\n", name);
 
 	/* allocate the device structure */
-	size = SIZEOF_STRUCT_MTD_CONCAT(num_devs);
-	concat = kzalloc(size, GFP_KERNEL);
+	concat = kzalloc_flex(*concat, subdev, num_devs, GFP_KERNEL);
 	if (!concat) {
 		printk
 		    ("memory allocation error while creating concatenated device \"%s\"\n",
 		     name);
 		return NULL;
 	}
-	concat->subdev = (struct mtd_info **) (concat + 1);
 
 	/*
 	 * Set up the new "super" device's MTD object structure, check for
diff --git a/include/linux/mtd/concat.h b/include/linux/mtd/concat.h
index 2cd9d48958a8..f8d4d6ac1fc1 100644
--- a/include/linux/mtd/concat.h
+++ b/include/linux/mtd/concat.h
@@ -18,7 +18,7 @@
 struct mtd_concat {
 	struct mtd_info mtd;
 	int num_subdev;
-	struct mtd_info **subdev;
+	struct mtd_info *subdev[];
 };
 
 struct mtd_info *mtd_concat_create(
-- 
2.53.0


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

      parent reply	other threads:[~2026-03-04 22:15 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-04 22:15 [PATCH 0/2] mtd: concat: use flex array Rosen Penev
2026-03-04 22:15 ` [PATCH 1/2] mtd: virt_concat: use single allocation for node Rosen Penev
2026-03-05  7:08   ` Philipp Matthias Hahn
2026-03-05  8:52     ` Rosen Penev
2026-03-04 22:15 ` Rosen Penev [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20260304221530.15018-3-rosenp@gmail.com \
    --to=rosenp@gmail.com \
    --cc=gustavoars@kernel.org \
    --cc=kees@kernel.org \
    --cc=linux-hardening@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mtd@lists.infradead.org \
    --cc=miquel.raynal@bootlin.com \
    --cc=richard@nod.at \
    --cc=vigneshr@ti.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox