FAILED: patch "[PATCH] mtd: nand: fix bug writing 1 byte less than page size" failed to apply to 3.14-stable tree

The patch below does not apply to the 3.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Hector Palacios <[email protected]>
Date: Mon, 18 Jul 2016 10:39:18 +0200
Subject: [PATCH] mtd: nand: fix bug writing 1 byte less than page size

nand_do_write_ops() determines if it is writing a partial page with the formula:

	part_pagewr = (column || writelen < (mtd->writesize - 1))

When 'writelen' is exactly 1 byte less than the NAND page size the formula equates to zero, so the code doesn't process it as a partial write, although it should.
As a consequence the function remains in the while(1) loop with 'writelen' becoming 0xffffffff and iterating endlessly.

The bug may not be easy to reproduce in Linux since user space tools usually force the padding or round-up the write size to a page-size multiple.
This was discovered in U-Boot where the issue can be reproduced by writing any size that is 1 byte less than a page-size multiple. For example, on a NAND with 2K page (0x800):
=> nand erase.part <partition>
=> nand write $loadaddr <partition> 7ff

[Editor's note: the bug was added in commit 29072b96078f, but moved around in commit 66507c7bc8895 ("mtd: nand: Add support to use nand_base poi databuf as bounce buffer")]

index 0b0dc29d2af7..77533f7f2429 100644
@@ -2610,7 +2610,7 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
 		int cached = writelen > bytes && page != blockmask;
 		uint8_t *wbuf = buf;
 		int use_bufpoi;
-		int part_pagewr = (column || writelen < (mtd->writesize - 1));
+		int part_pagewr = (column || writelen < mtd->writesize);
 
 		if (part_pagewr)
 			use_bufpoi = 1;