The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From dbc626597c39b24cefce09fbd8e9dea85869a801 Mon Sep 17 00:00:00 2001

From: Ross Zwisler ross.zwisler@linux.intel.com Date: Tue, 26 Jun 2018 16:30:41 -0600 Subject: [PATCH] dm: prevent DAX mounts if not supported

Currently device_supports_dax() just checks to see if the QUEUE_FLAG_DAX flag is set on the device's request queue to decide whether or not the device supports filesystem DAX. Really we should be using bdev_dax_supported() like filesystems do at mount time. This performs other tests like checking to make sure the dax_direct_access() path works.

We also explicitly clear QUEUE_FLAG_DAX on the DM device's request queue if any of the underlying devices do not support DAX. This makes the handling of QUEUE_FLAG_DAX consistent with the setting/clearing of most other flags in dm_table_set_restrictions().

Now that bdev_dax_supported() explicitly checks for QUEUE_FLAG_DAX, this will ensure that filesystems built upon DM devices will only be able to mount with DAX if all underlying devices also support DAX.

Signed-off-by: Ross Zwisler ross.zwisler@linux.intel.com Fixes: commit 545ed20e6df6 ("dm: add infrastructure for DAX support") Cc: stable@vger.kernel.org Acked-by: Dan Williams dan.j.williams@intel.com Reviewed-by: Toshi Kani toshi.kani@hpe.com Signed-off-by: Mike Snitzer snitzer@redhat.com

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 938766794c2e..3d0e2c198f06 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -885,9 +885,7 @@ EXPORT_SYMBOL_GPL(dm_table_set_type); static int device_supports_dax(struct dm_target *ti, struct dm_dev *dev, sector_t start, sector_t len, void *data) { - struct request_queue *q = bdev_get_queue(dev->bdev); - - return q && blk_queue_dax(q); + return bdev_dax_supported(dev->bdev, PAGE_SIZE); }

static bool dm_table_supports_dax(struct dm_table *t) @@ -1907,6 +1905,9 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,

if (dm_table_supports_dax(t)) blk_queue_flag_set(QUEUE_FLAG_DAX, q); + else + blk_queue_flag_clear(QUEUE_FLAG_DAX, q); + if (dm_table_supports_dax_write_cache(t)) dax_write_cache(t->md->dax_dev, true);

diff --git a/drivers/md/dm.c b/drivers/md/dm.c index a3b103e8e3ce..b0dd7027848b 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1056,8 +1056,7 @@ static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, if (len < 1) goto out; nr_pages = min(len, nr_pages); - if (ti->type->direct_access) - ret = ti->type->direct_access(ti, pgoff, nr_pages, kaddr, pfn); + ret = ti->type->direct_access(ti, pgoff, nr_pages, kaddr, pfn);

out: dm_put_live_table(md, srcu_idx);