[PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling

From: Ross Zwisler
Date: Fri Nov 13 2015 - 19:15:14 EST

Currently the PMEM driver doesn't accept REQ_FLUSH or REQ_FUA bios. These
are sent down via blkdev_issue_flush() in response to a fsync() or msync()
and are used by filesystems to order their metadata, among other things.

When we get an msync() or fsync() it is the responsibility of the DAX code
to flush all dirty pages to media. The PMEM driver then just has issue a
wmb_pmem() in response to the REQ_FLUSH to ensure that before we return all
the flushed data has been durably stored on the media.

Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
drivers/nvdimm/pmem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 0ba6a97..b914d66 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -80,7 +80,7 @@ static void pmem_make_request(struct request_queue *q, struct bio *bio)
if (do_acct)
nd_iostat_end(bio, start);

- if (bio_data_dir(bio))
+ if (bio_data_dir(bio) || (bio->bi_rw & (REQ_FLUSH|REQ_FUA)))

@@ -189,6 +189,7 @@ static int pmem_attach_disk(struct device *dev,
blk_queue_physical_block_size(pmem->pmem_queue, PAGE_SIZE);
blk_queue_max_hw_sectors(pmem->pmem_queue, UINT_MAX);
blk_queue_bounce_limit(pmem->pmem_queue, BLK_BOUNCE_ANY);
+ blk_queue_flush(pmem->pmem_queue, REQ_FLUSH|REQ_FUA);
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, pmem->pmem_queue);

disk = alloc_disk(0);

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