The new writethrough strategy for dm-cache issues a bio to the origin device,
remaps the bio to the cache device, and issues the bio to the cache device.
However, the block layer modifies bi_sector and bi_size, so we need to preserve
these or else nothing gets written to the cache (bi_size == 0). This fixes the
problem where someone writes a block through the cache, but a subsequent reread
(from the cache) returns old contents.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
drivers/md/dm-cache-target.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 66120bd..0db0ad2 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -205,6 +205,8 @@ struct per_bio_data {
struct cache *cache;
dm_cblock_t cblock;
bio_end_io_t *saved_bi_end_io;
+ unsigned int bi_size;
+ sector_t bi_sector;
};
struct dm_cache_migration {
@@ -643,6 +645,8 @@ static void writethrough_endio(struct bio *bio, int err)
return;
}
+ bio->bi_sector = pb->bi_sector;
+ bio->bi_size = pb->bi_size;
remap_to_cache(pb->cache, bio, pb->cblock);
/*
@@ -667,6 +671,12 @@ static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio,
pb->cache = cache;
pb->cblock = cblock;
pb->saved_bi_end_io = bio->bi_end_io;
+ /*
+ * The block layer modifies bi_size and bi_sector, so we must save
+ * them for when we re-issue the bio against the cache device.
+ */
+ pb->bi_size = bio->bi_size;
+ pb->bi_sector = bio->bi_sector;
bio->bi_end_io = writethrough_endio;
remap_to_origin_clear_discard(pb->cache, bio, oblock);
--
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