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Subject[PATCH v2 0/7] Fix DM DAX handling
Date
Changes from v1:
* Reworked patches 1 and 2 so that the __bdev_dax_supported() function
stays hidden behind the bdev_dax_supported() wrapper. This is needed
to prevent compilation errors in configs where CONFIG_FS_DAX isn't
defined. (0-day)

* Added Eric's Reviewed-by to patch 1. I did this in spite of the
bdev_dax_supported() changes because they were minor and I think
Eric's review was focused on the XFS parts.

---

This series fixes a few issues that I found with DM's handling of DAX
devices. Here are some of the issues I found:

* We can create a dm-stripe or dm-linear device which is made up of an
fsdax PMEM namespace and a raw PMEM namespace but which can hold a
filesystem mounted with the -o dax mount option. DAX operations to
the raw PMEM namespace part lack struct page and can fail in
interesting/unexpected ways when doing things like fork(), examining
memory with gdb, etc.

* We can create a dm-stripe or dm-linear device which is made up of an
fsdax PMEM namespace and a BRD ramdisk which can hold a filesystem
mounted with the -o dax mount option. All I/O to this filesystem
will fail.

* In DM you can't transition a dm target which could possibly support
DAX (mode DM_TYPE_DAX_BIO_BASED) to one which can't support DAX
(mode DM_TYPE_BIO_BASED), even if you never use DAX.

The first 2 patches in this series are prep work from Darrick and Dave
which improve bdev_dax_supported(). The last 5 problems fix the above
mentioned problems in DM. I feel that this series simplifies the
handling of DAX devices in DM, and the last 5 DM-related patches have a
net code reduction of 50 lines.

Darrick J. Wong (1):
fs: allow per-device dax status checking for filesystems

Dave Jiang (1):
dax: change bdev_dax_supported() to support boolean returns

Ross Zwisler (5):
dm: fix test for DAX device support
dm: prevent DAX mounts if not supported
dm: remove DM_TYPE_DAX_BIO_BASED dm_queue_mode
dm-snap: remove unnecessary direct_access() stub
dm-error: remove unnecessary direct_access() stub

drivers/dax/super.c | 40 ++++++++++++++++++++--------------------
drivers/md/dm-ioctl.c | 16 ++++++----------
drivers/md/dm-snap.c | 8 --------
drivers/md/dm-table.c | 29 +++++++++++------------------
drivers/md/dm-target.c | 7 -------
drivers/md/dm.c | 7 ++-----
fs/ext2/super.c | 3 +--
fs/ext4/super.c | 3 +--
fs/xfs/xfs_ioctl.c | 3 ++-
fs/xfs/xfs_iops.c | 30 +++++++++++++++++++++++++-----
fs/xfs/xfs_super.c | 10 ++++++++--
include/linux/dax.h | 11 ++++++-----
include/linux/device-mapper.h | 8 ++++++--
13 files changed, 88 insertions(+), 87 deletions(-)

--
2.14.3

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