Commit d22d5f47 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Miquel Raynal
Browse files

mtd: nftl: reduce stack usage in NFTL_movebuf() 



The code in the ntfl write function is rather complex, and it contains
a 512 byte on-stack buffer. The combination of these two leads to using
more than the per-function stack warning limit in some configurations,
especially with KASAN enabled:

drivers/mtd/nftlcore.c:673:12: error: stack frame size (1328) exceeds limit (1280) in 'nftl_writeblock' [-Werror,-Wframe-larger-than]

Avoid this warning by moving the on-stack buffer into a separate function
that only copies one part of the device to another.

This does not really help with the total maximum stack usage in the
(non-KASAN) normal case, but it does two things:

 - no single function has more than the warning limit
 - the complexity goes down, so the parent function ends up
   spilling few local variables, and the total actually goes
   down slightly.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarMiquel Raynal <miquel.raynal@bootlin.com>
parent 27b045eb

drivers/mtd/nftlcore.c

+21 −22
Original line number Diff line number Diff line
@@ -228,6 +228,25 @@ static u16 NFTL_findfreeblock(struct NFTLrecord *nftl, int desperate ) 
	return BLOCK_NIL;

}



static noinline_for_stack void NFTL_move_block(struct mtd_info *mtd, loff_t src, loff_t dst)

{

	unsigned char movebuf[512];

	struct nftl_oob oob;

	size_t retlen;

	int ret;



	ret = mtd_read(mtd, src, 512, &retlen, movebuf);

	if (ret < 0 && !mtd_is_bitflip(ret)) {

		ret = mtd_read(mtd, src, 512, &retlen, movebuf);

		if (ret != -EIO)

			printk("Error went away on retry.\n");

	}

	memset(&oob, 0xff, sizeof(struct nftl_oob));

	oob.b.Status = oob.b.Status1 = SECTOR_USED;



	nftl_write(mtd, dst, 512, &retlen, movebuf, (char *)&oob);

}



static u16 NFTL_foldchain (struct NFTLrecord *nftl, unsigned thisVUC, unsigned pendingblock )

{

	struct mtd_info *mtd = nftl->mbd.mtd;
@@ -389,9 +408,6 @@ static u16 NFTL_foldchain (struct NFTLrecord *nftl, unsigned thisVUC, unsigned p 
	*/

	pr_debug("Folding chain %d into unit %d\n", thisVUC, targetEUN);

	for (block = 0; block < nftl->EraseSize / 512 ; block++) {

		unsigned char movebuf[512];

		int ret;



		/* If it's in the target EUN already, or if it's pending write, do nothing */

		if (BlockMap[block] == targetEUN ||

		    (pendingblock == (thisVUC * (nftl->EraseSize / 512) + block))) {
@@ -403,25 +419,8 @@ static u16 NFTL_foldchain (struct NFTLrecord *nftl, unsigned thisVUC, unsigned p 
		if (BlockMap[block] == BLOCK_NIL)

			continue;



		ret = mtd_read(mtd,

			       (nftl->EraseSize * BlockMap[block]) + (block * 512),

			       512,

			       &retlen,

			       movebuf);

		if (ret < 0 && !mtd_is_bitflip(ret)) {

			ret = mtd_read(mtd,

				       (nftl->EraseSize * BlockMap[block]) + (block * 512),

				       512,

				       &retlen,

				       movebuf);

			if (ret != -EIO)

				printk("Error went away on retry.\n");

		}

		memset(&oob, 0xff, sizeof(struct nftl_oob));

		oob.b.Status = oob.b.Status1 = SECTOR_USED;



		nftl_write(nftl->mbd.mtd, (nftl->EraseSize * targetEUN) +

			   (block * 512), 512, &retlen, movebuf, (char *)&oob);

		NFTL_move_block(mtd, (nftl->EraseSize * BlockMap[block]) + (block * 512),

				(nftl->EraseSize * targetEUN) + (block * 512));

	}



	/* add the header so that it is now a valid chain */