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super1: make write_bitmap1 compatible with previous mdadm versions 

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@derobert.net>
Fixes: 95a05b37e8 ("Create n bitmaps for clustered mode")
Cc: Neil Brown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
This commit is contained in:
Guoqing Jiang 2016-10-12 02:24:07 -04:00 committed by Jes Sorensen
parent 681b7ae245
commit 119b66a473
1 changed files with 9 additions and 1 deletions
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10
super1.c
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@ -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)