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Commit 8089ed79 authored by Artem Bityutskiy's avatar Artem Bityutskiy
Browse files

UBIFS: fix power cut emulation for mtdram 



The power cut emulation did not work correctly because we corrupted more than
one max. I/O unit in the buffer and then wrote the entire buffer. This lead to
recovery errors because UBIFS complained about corrupted free space. And this
was easily reproducible on mtdram because max. write size is very small there
(64 bytes), and we could easily have a 1KiB buffer, corrupt 128 bytes there,
and then write the entire buffer.

The fix is to corrupt max. write size bytes at most, and write only up to the
last corrupted max. write size chunk, not the entire buffer.

Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
parent 4b3e58a6

fs/ubifs/debug.c

+11 −9
Original line number Diff line number Diff line
@@ -2646,18 +2646,16 @@ static int power_cut_emulated(struct ubifs_info *c, int lnum, int write) 
	return 1;

}



static void cut_data(const void *buf, unsigned int len)

static int corrupt_data(const struct ubifs_info *c, const void *buf,

			unsigned int len)

{

	unsigned int from, to, i, ffs = chance(1, 2);

	unsigned char *p = (void *)buf;



	from = random32() % (len + 1);

	if (chance(1, 2))

		to = random32() % (len - from + 1);

	else

		to = len;

	/* Corruption may only span one max. write unit */

	to = min(len, ALIGN(from, c->max_write_size));



	if (from < to)

	ubifs_warn("filled bytes %u-%u with %s", from, to - 1,

		   ffs ? "0xFFs" : "random data");
@@ -2667,6 +2665,8 @@ static void cut_data(const void *buf, unsigned int len) 
	else

		for (i = from; i < to; i++)

			p[i] = random32() % 0x100;



	return to;

}



int dbg_leb_write(struct ubifs_info *c, int lnum, const void *buf,
@@ -2679,7 +2679,9 @@ int dbg_leb_write(struct ubifs_info *c, int lnum, const void *buf, 


	failing = power_cut_emulated(c, lnum, 1);

	if (failing)

		cut_data(buf, len);

		len = corrupt_data(c, buf, len);

	ubifs_warn("actually write %d bytes to LEB %d:%d (the buffer was corrupted)",

		   len, lnum, offs);

	err = ubi_leb_write(c->ubi, lnum, buf, offs, len);

	if (err)

		return err;