For older mdadm version, v1.x metadata has different bitmap_offset, we can't ensure all the bitmaps are on a 4K boundary since writing 4K for bitmap could corrupt the superblock, and Anthony reported the bug about it at below link. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=837964 So let's check about the alignment for bitmap_offset before set the boundary to 4096 unconditionally. Thanks for Neil's detailed explanation. Reported-by: Anthony DeRobertis <anthony@xxxxxxxxxxxx> Fixes: 95a05b37e8eb ("Create n bitmaps for clustered mode") Cc: Neil Brown <neilb@xxxxxxxx> Signed-off-by: Guoqing Jiang <gqjiang@xxxxxxxx> --- super1.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/super1.c b/super1.c index 9f62d23..4fef378 100644 --- a/super1.c +++ b/super1.c @@ -2433,7 +2433,15 @@ static int write_bitmap1(struct supertype *st, int fd, enum bitmap_update update memset(buf, 0xff, 4096); memcpy(buf, (char *)bms, sizeof(bitmap_super_t)); - towrite = calc_bitmap_size(bms, 4096); + /* + * use 4096 boundary if bitmap_offset is aligned + * with 8 sectors, then it should compatible with + * older mdadm. + */ + if (__le32_to_cpu(sb->bitmap_offset) & 7) + towrite = calc_bitmap_size(bms, 512); + else + towrite = calc_bitmap_size(bms, 4096); while (towrite > 0) { n = towrite; if (n > 4096) -- 2.6.6 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
