md/bitmap: copy correct data for bitmap super
authorShaohua Li <shli@fb.com>
Thu, 17 Aug 2017 17:35:11 +0000 (10:35 -0700)
committerShaohua Li <shli@fb.com>
Thu, 24 Aug 2017 17:04:54 +0000 (10:04 -0700)
commit8031c3ddc70ab93099e7d1814382dba39f57b43e
treebbcde9109d222c1e224d077f121fd7e6e9940194
parent143c97cc652949893c8056c679012f0aeccb80e5
md/bitmap: copy correct data for bitmap super

raid5 cache could write bitmap superblock before bitmap superblock is
initialized. The bitmap superblock is less than 512B. The current code will
only copy the superblock to a new page and write the whole 512B, which will
zero the the data after the superblock. Unfortunately the data could include
bitmap, which we should preserve. The patch will make superblock read do 4k
chunk and we always copy the 4k data to new page, so the superblock write will
old data to disk and we don't change the bitmap.

Reported-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Cc: stable@vger.kernel.org (4.10+)
Signed-off-by: Shaohua Li <shli@fb.com>
drivers/md/bitmap.c