linux-ext4 - [PATCH 0/8] dax fixes / cleanups: pmd vs thp, lifetime, and locking

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Message-ID: <20151117201551.15053.32709.stgit@dwillia2-desk3.jf.intel.com>
Date:	Tue, 17 Nov 2015 12:15:52 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	linux-nvdimm@...ts.01.org
Cc:	Jan Kara <jack@...e.com>, Boaz Harrosh <boaz@...xistor.com>,
	Theodore Ts'o <tytso@....edu>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Dave Chinner <david@...morbit.com>,
	Yigal Korman <yigal@...xistor.com>, stable@...r.kernel.org,
	Jens Axboe <axboe@...com>, Jeff Moyer <jmoyer@...hat.com>,
	linux-block@...r.kernel.org,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	Dave Chinner <dchinner@...hat.com>,
	linux-fsdevel@...r.kernel.org, willy@...ux.intel.com,
	ross.zwisler@...ux.intel.com, linux-ext4@...r.kernel.org,
	akpm@...ux-foundation.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 0/8] dax fixes / cleanups: pmd vs thp, lifetime, and locking

Changes since last posting [1]:

1/ Further cleanups to dax_clear_blocks(): Dropped increments of 'addr'
   since we call bdev_direct_access() before the next use, and dropped the
   BUG_ON for sector unaligned return values from bdev_direct_access().

2/ In [PATCH 8/8] introduce blk_dax_ctl to remove the need to have
   separate dax_map_atomic and __dax_map_atomic routines.  Note,
   blk_dax_ctl is not passed through to drivers, it gets unpacked in
   bdev_direct_access.  (Willy)

3/ New [PATCH 2/8]: Disable huge page dax mappings while we resolve
   various crash scenarios in this development cycle.

4/ New [PATCH 4/8]: Unmap all dax mappings at block device shutdown

I have kept the reviewed-by's received to date, let me know if these
incremental updates invalidate that review.

[1]: https://lists.01.org/pipermail/linux-nvdimm/2015-November/002733.html

---

The first 4 patches in this series I consider 4.4-rc / -stable material.
The rest are for 4.5.  [PATCH 4/8] needs scrutiny.  It is yet another
example of where DAX behavior necessarily differs from page cache
behavior.  I still maintain that we should not be surprising unaware
applications with DAX semantics, i.e. that DAX should be per-inode
opt-in, not globally enabled for all inodes at fs mount time.

The largest patch in the set, [PATCH 8/8], addresses the lifetime of the
'addr' returned by bdev_direct_access.  That address is only valid while
the device driver is enabled.  The new dax_map_atomic() /
dax_unmap_atomic() pairing guarantees that 'addr' stays valid for the
duration of that mapping.

While dax_map_atomic() protects against 'addr' going invalid, the new
calls to truncate_pagecache() via invalidate_inodes() protect against
the 'pfn' returned from bdev_direct_access() going invalid.  Otherwise,
the storage media can be directly accessed after the driver has been
disabled.

---

[PATCH 1/8] ext2, ext4: warn when mounting with dax enabled
[PATCH 2/8] dax: disable pmd mappings
[PATCH 3/8] mm, dax: fix DAX deadlocks (COW fault)
[PATCH 4/8] mm, dax: truncate dax mappings at bdev or fs shutdown
[PATCH 5/8] pmem, dax: clean up clear_pmem()
[PATCH 6/8] dax: increase granularity of dax_clear_blocks() operations
[PATCH 7/8] dax: guarantee page aligned results from bdev_direct_access()
[PATCH 8/8] dax: fix lifetime of in-kernel dax mappings with dax_map_atomic()

 arch/x86/include/asm/pmem.h |    7 -
 block/blk.h                 |    2 
 fs/Kconfig                  |    6 +
 fs/block_dev.c              |   15 +--
 fs/dax.c                    |  228 ++++++++++++++++++++++++++-----------------
 fs/ext2/super.c             |    2 
 fs/ext4/super.c             |    6 +
 fs/inode.c                  |   27 +++++
 include/linux/blkdev.h      |   19 +++-
 mm/memory.c                 |    8 +-
 mm/truncate.c               |   13 ++
 11 files changed, 217 insertions(+), 116 deletions(-)
--
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