Hi Brian, >From: Brian Norris [mailto:computersforpeace@xxxxxxxxx] >>On Fri, Dec 13, 2013 at 02:42:57PM +0530, Pekon Gupta wrote: >> This patch updates starting offset for free bytes in OOB which can be used by >> file-systems to store their metadata (like clean-marker in case of JFFS2). > >This should be describing a regression fix, right? We don't just >arbitrarily change the "OOB free" layout; we need a reason. So please >describe it here. > >(It seems like an off-by-one, or off-by-<N> error, where the oobfree >region was miscalculated.) > >Possibly you can paste an example intended ecclayout as well as an >incorrect layout that was calculated before this fix. > >> Signed-off-by: Pekon Gupta <pekon@xxxxxx> >> --- >> drivers/mtd/nand/omap2.c | 17 ++++------------- >> 1 file changed, 4 insertions(+), 13 deletions(-) >> >> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c [...] >> >> - /* populate remaining ECC layout data */ >> - ecclayout->oobfree->length = mtd->oobsize - (BADBLOCK_MARKER_LENGTH + >> - ecclayout->eccbytes); >> for (i = 1; i < ecclayout->eccbytes; i++) >> ecclayout->eccpos[i] = ecclayout->eccpos[0] + i; >> /* check if NAND device's OOB is enough to store ECC signatures */ >> @@ -1990,6 +1977,10 @@ static int omap_nand_probe(struct platform_device *pdev) >> err = -EINVAL; >> goto return_error; >> } >> + /* populate remaining ECC layout data */ >> + ecclayout->oobfree->offset = ecclayout->eccpos[ecclayout->eccbytes] + 1; > >Hmm, this line seems a little odd. The ecclayout->eccpos[] array and the >value of ecclayout->eccbytes sould be related as follows: > > let N = ecclayout->eccbytes > > This means the eccpos[] array should have N entries, indexed 0 to N-1, > and eccpos[N] is out of bounds. But you are accessing eccpos[N] above > (i.e., eccpos[ecclayout->eccbytes]). Are you sure this is correct? It > seems like it should be: > > ecclayout->oobfree->offset = ecclayout->eccpos[ecclayout->eccbytes - 1] + 1; > Thanks for this catch. Yes, you are correct. It's a typo. This wasn't caught as I had tested everything on UBIFS which does not use 'oobfree'. Also, as ecclayout->eccpos is defined as large static array, so this dint caused problems either. #define MTD_MAX_ECCPOS_ENTRIES_LARGE 640 struct nand_ecclayout { __u32 eccpos[MTD_MAX_ECCPOS_ENTRIES_LARGE]; But, I think mtd_tests.nand_oobtest would have caught this. I'll include this change in next version. <stripping down the CC list to avoid getting moderated by u-boot mailman> with regards, pekon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
