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mtd: nftl: reduce stack usage in NFTL_movebuf()

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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: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
This commit is contained in:
Arnd Bergmann
2025-06-10 11:25:22 +02:00
committed by Miquel Raynal
parent 27b045eb3e
commit d22d5f47ec
1 changed files with 21 additions and 22 deletions
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43
drivers/mtd/nftlcore.c
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@@ -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 */