From 8089ed792832e5d3dd219da435c5a08d969662b4 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Wed, 22 Aug 2012 17:35:11 +0300 Subject: [PATCH] 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: Artem Bityutskiy --- fs/ubifs/debug.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c index 1aaa9f51948..5dc993fdca8 100644 --- a/fs/ubifs/debug.c +++ b/fs/ubifs/debug.c @@ -2646,20 +2646,18 @@ 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"); + ubifs_warn("filled bytes %u-%u with %s", from, to - 1, + ffs ? "0xFFs" : "random data"); if (ffs) for (i = from; i < to; i++) @@ -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;