These methods indirect the actual DAX read/write path.  In the end pmem
uses magic flush and mc safe variants and fuse and dcssblk use plain ones
while device mapper picks redirects to the underlying device.

Add set_dax_nocache() and set_dax_nomc() APIs to control which copy
routines are used to remove indirect call from the read/write fast path
as well as a lot of boilerplate code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com> [virtiofs]
Link: https://lore.kernel.org/r/20211215084508.435401-5-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Remove the last user of ->bdev in dax.c by requiring the file system to
pass in an address that already includes the DAX offset.  As part of the
only set ->bdev or ->daxdev when actually required in the ->iomap_begin
methods.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com> [erofs]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-27-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Add a flag so that the file system can easily detect DAX operations
based just on the iomap operation requested instead of looking at
inode state using IS_DAX.  This will be needed to apply the to be
added partition offset only for operations that actually use DAX,
but not things like fiemap that are based on the block device.
In the long run it should also allow turning the bdev, dax_dev
and inline_data into a union.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-25-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Unshare the DAX and iomap buffered I/O page zeroing code.  This code
previously did a IS_DAX check deep inside the iomap code, which in
fact was the only DAX check in the code.  Instead move these checks
into the callers.  Most callers already have DAX special casing anyway
and XFS will need it for reflink support as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-19-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Factor out a helper for the "manual" zeroing of a DAX range to clean
up dax_iomap_zero a lot.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-18-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The file relative offset must have the same alignment as the storage
offset, so use that and get rid of the call to iomap_sector.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-17-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Replace the two steps of dax_iomap_sector and bdev_dax_pgoff with a
single dax_iomap_pgoff helper that avoids lots of cumbersome sector
conversions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-15-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Just pass the vm_fault and iomap_iter structures, and figure out the rest
locally.  Note that this requires moving dax_iomap_sector up in the file.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-14-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Despite its name copy_user_page expected kernel addresses, which is what
we already have.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-13-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Avoid the open coded calls to ->iomap_begin and ->iomap_end and call
iomap_iter instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

The core logic in the two dax page fault functions is similar. So, move
the logic into a common helper function. Also, to facilitate the
addition of new features, such as CoW, switch-case is no longer used to
handle different iomap types.

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

The dax page fault code is too long and a bit difficult to read. And it
is hard to understand when we trying to add new features. Some of the
PTE/PMD codes have similar logic. So, factor out helper functions to
simplify the code.

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[hch: minor cleanups]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

Switch the dax_iomap_rw implementation to use iomap_iter.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

dax_direct_access() takes a number of pages.  PHYS_PFN(PAGE_SIZE) is a
very round about way to specify '1'.

Change the nr_pages parameter to the explicit value of '1'.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20210525172428.3634316-3-ira.weiny@intel.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

grab_mapping_entry() has a bug in handling of ENOMEM condition.  Suppose
we have a PMD entry at index i which we are downgrading to a PTE entry.
grab_mapping_entry() will set pmd_downgrade to true, lock the entry, clear
the entry in xarray, and decrement mapping->nrpages.  The it will call:

	entry = dax_make_entry(pfn_to_pfn_t(0), flags);
	dax_lock_entry(xas, entry);

which inserts new PTE entry into xarray.  However this may fail allocating
the new node.  We handle this by:

	if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM))
		goto retry;

however pmd_downgrade stays set to true even though 'entry' returned from
get_unlocked_entry() will be NULL now.  And we will go again through the
downgrade branch.  This is mostly harmless except that mapping->nrpages is
decremented again and we temporarily have an invalid entry stored in
xarray.  Fix the problem by setting pmd_downgrade to false each time we
lookup the entry we work with so that it matches the entry we found.

Link: https://lkml.kernel.org/r/20210622160015.18004-1-jack@suse.cz


Fixes: b15cd800 ("dax: Convert page fault handlers to XArray")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

I am seeing missed wakeups which ultimately lead to a deadlock when I am
using virtiofs with DAX enabled and running "make -j". I had to mount
virtiofs as rootfs and also reduce to dax window size to 256M to reproduce
the problem consistently.

So here is the problem. put_unlocked_entry() wakes up waiters only
if entry is not null as well as !dax_is_conflict(entry). But if I
call multiple instances of invalidate_inode_pages2() in parallel,
then I can run into a situation where there are waiters on
this index but nobody will wake these waiters.

invalidate_inode_pages2()
  invalidate_inode_pages2_range()
    invalidate_exceptional_entry2()
      dax_invalidate_mapping_entry_sync()
        __dax_invalidate_entry() {
                xas_lock_irq(&xas);
                entry = get_unlocked_entry(&xas, 0);
                ...
                ...
                dax_disassociate_entry(entry, mapping, trunc);
                xas_store(&xas, NULL);
                ...
                ...
                put_unlocked_entry(&xas, entry);
                xas_unlock_irq(&xas);
        }

Say a fault in in progress and it has locked entry at offset say "0x1c".
Now say three instances of invalidate_inode_pages2() are in progress
(A, B, C) and they all try to invalidate entry at offset "0x1c". Given
dax entry is locked, all tree instances A, B, C will wait in wait queue.

When dax fault finishes, say A is woken up. It will store NULL entry
at index "0x1c" and wake up B. When B comes along it will find "entry=0"
at page offset 0x1c and it will call put_unlocked_entry(&xas, 0). And
this means put_unlocked_entry() will not wake up next waiter, given
the current code. And that means C continues to wait and is not woken
up.

This patch fixes the issue by waking up all waiters when a dax entry
has been invalidated. This seems to fix the deadlock I am facing
and I can make forward progress.

Reported-by: Sergio Lopez <slp@redhat.com>
Fixes: ac401cc7 ("dax: New fault locking")
Reviewed-by: Jan Kara <jack@suse.cz>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20210428190314.1865312-4-vgoyal@redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

As of now put_unlocked_entry() always wakes up next waiter. In next
patches we want to wake up all waiters at one callsite. Hence, add a
parameter to the function.

This patch does not introduce any change of behavior.

Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20210428190314.1865312-3-vgoyal@redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Dan mentioned that he is not very fond of passing around a boolean true/false
to specify if only next waiter should be woken up or all waiters should be
woken up. He instead prefers that we introduce an enum and make it very
explicity at the callsite itself. Easier to read code.

This patch should not introduce any change of behavior.

Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20210428190314.1865312-2-vgoyal@redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Simplify mapping_needs_writeback() by accounting DAX entries as pages
instead of exceptional entries.

Link: https://lkml.kernel.org/r/20201026151849.24232-4-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Vishal Verma <vishal.l.verma@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "Remove nrexceptional tracking", v2.

We actually use nrexceptional for very little these days.  It's a minor
pain to keep in sync with nrpages, but the pain becomes much bigger with
the THP patches because we don't know how many indices a shadow entry
occupies.  It's easier to just remove it than keep it accurate.

Also, we save 8 bytes per inode which is nothing to sneeze at; on my
laptop, it would improve shmem_inode_cache from 22 to 23 objects per
16kB, and inode_cache from 26 to 27 objects.  Combined, that saves
a megabyte of memory from a combined usage of 25MB for both caches.
Unfortunately, ext4 doesn't cross a magic boundary, so it doesn't save
any memory for ext4.

This patch (of 4):

Instead of checking the two counters (nrpages and nrexceptional), we can
just check whether i_pages is empty.

Link: https://lkml.kernel.org/r/20201026151849.24232-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20201026151849.24232-2-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Vishal Verma <vishal.l.verma@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Currently, the follow_pfn function is exported for modules but
follow_pte is not.  However, follow_pfn is very easy to misuse,
because it does not provide protections (so most of its callers
assume the page is writable!) and because it returns after having
already unlocked the page table lock.

Provide instead a simplified version of follow_pte that does
not have the pmdpp and range arguments.  The older version
survives as follow_invalidate_pte() for use by fs/dax.c.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Merge __follow_pte_pmd, follow_pte_pmd and follow_pte into a single
follow_pte function and just pass two additional NULL arguments for the
two previous follow_pte callers.

[sfr@canb.auug.org.au: merge fix for "s390/pci: remove races against pte updates"]
  Link: https://lkml.kernel.org/r/20201111221254.7f6a3658@canb.auug.org.au

Link: https://lkml.kernel.org/r/20201029101432.47011-3-hch@lst.de


Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pass the full length to iomap_zero() and dax_iomap_zero(), and have
them return how many bytes they actually handled.  This is preparatory
work for handling THP, although it looks like DAX could actually take
advantage of it if there's a larger contiguous area.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

virtiofs device has a range of memory which is mapped into file inodes
using dax. This memory is mapped in qemu on host and maps different
sections of real file on host. Size of this memory is limited
(determined by administrator) and depending on filesystem size, we will
soon reach a situation where all the memory is in use and we need to
reclaim some.

As part of reclaim process, we will need to make sure that there are
no active references to pages (taken by get_user_pages()) on the memory
range we are trying to reclaim. I am planning to use
dax_layout_busy_page() for this. But in current form this is per inode
and scans through all the pages of the inode.

We want to reclaim only a portion of memory (say 2MB page). So we want
to make sure that only that 2MB range of pages do not have any
references  (and don't want to unmap all the pages of inode).

Hence, create a range version of this function named
dax_layout_busy_page_range() which can be used to pass a range which
needs to be unmapped.

Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm@lists.01.org
Cc: Jan Kara <jack@suse.cz>
Cc: Vishal L Verma <vishal.l.verma@intel.com>
Cc: "Weiny, Ira" <ira.weiny@intel.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through



Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

The argument passed to xas_set_err() to indicate an error should be negative.
Otherwise, xas_error() will return 0, and grab_mapping_entry() will return the
found entry instead of 'SIGBUS' when the entry is not in fact valid.
This would result in problems in subsequent code paths.

Link: https://lore.kernel.org/r/20200729034436.24267-1-lihao2018.fnst@cn.fujitsu.com


Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: Hao Li <lihao2018.fnst@cn.fujitsu.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

Passing size to copy_user_dax implies it can copy variable sizes of data
when in fact it calls copy_user_page() which is exactly a page.

We are safe because the only caller uses PAGE_SIZE anyway so just remove
the variable for clarity.

While we are at it change copy_user_dax() to copy_cow_page_dax() to make
it clear it is a singleton helper for this one case not implementing
what dax_iomap_actor() does.

Link: https://lore.kernel.org/r/20200717072056.73134-11-ira.weiny@intel.com


Reviewed-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

Add a helper dax_ioamp_zero() to zero a range. This patch basically
merges __dax_zero_page_range() and iomap_dax_zero().

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20200228163456.1587-7-vgoyal@redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Use new dax native zero page method for zeroing page if I/O is page
aligned. Otherwise fall back to direct_access() + memcpy().

This gets rid of one of the depenendency on block device in dax path.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20200228163456.1587-6-vgoyal@redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

fstests generic/471 reports a failure when run with MOUNT_OPTIONS="-o
dax".  The reason is that the initial pwrite to an empty file with the
RWF_NOWAIT flag set does not return -EAGAIN.  It turns out that
dax_iomap_rw doesn't pass that flag through to iomap_apply.

With this patch applied, generic/471 passes for me.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/x49r1z86e1d.fsf@segfault.boston.devel.redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

As of now dax_writeback_mapping_range() takes "struct block_device" as a
parameter and dax_dev is searched from bdev name. This also involves taking
a fresh reference on dax_dev and putting that reference at the end of
function.

We are developing a new filesystem virtio-fs and using dax to access host
page cache directly. But there is no block device. IOW, we want to make
use of dax but want to get rid of this assumption that there is always
a block device associated with dax_dev.

So pass in "struct dax_device" as parameter instead of bdev.

ext2/ext4/xfs are current users and they already have a reference on
dax_device. So there is no need to take reference and drop reference to
dax_device on each call of this function.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20200103183307.GB13350@redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Users reported a v5.3 performance regression and inability to establish
huge page mappings. A revised version of the ndctl "dax.sh" huge page
unit test identifies commit 23c84eb7 "dax: Fix missed wakeup with
PMD faults" as the source.

Update get_unlocked_entry() to check for NULL entries before checking
the entry order, otherwise NULL is misinterpreted as a present pte
conflict. The 'order' check needs to happen before the locked check as
an unlocked entry at the wrong order must fallback to lookup the correct
order.

Reported-by: Jeff Smits <jeff.smits@intel.com>
Reported-by: Doug Nelson <doug.nelson@intel.com>
Cc: <stable@vger.kernel.org>
Fixes: 23c84eb7 ("dax: Fix missed wakeup with PMD faults")
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Link: https://lore.kernel.org/r/157167532455.3945484.11971474077040503994.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The srcmap is used to identify where the read is to be performed from.
It is passed to ->iomap_begin, which can fill it in if we need to read
data for partially written blocks from a different location than the
write target.  The srcmap is only supported for buffered writes so far.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
[hch: merged two patches, removed the IOMAP_F_COW flag, use iomap as
      srcmap if not set, adjust length down to srcmap end as well]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

Vivek:

    "As of now dax_layout_busy_page() calls unmap_mapping_range() with last
     argument as 1, which says even unmap cow pages. I am wondering who needs
     to get rid of cow pages as well.

     I noticed one interesting side affect of this. I mount xfs with -o dax and
     mmaped a file with MAP_PRIVATE and wrote some data to a page which created
     cow page. Then I called fallocate() on that file to zero a page of file.
     fallocate() called dax_layout_busy_page() which unmapped cow pages as well
     and then I tried to read back the data I wrote and what I get is old
     data from persistent memory. I lost the data I had written. This
     read basically resulted in new fault and read back the data from
     persistent memory.

     This sounds wrong. Are there any users which need to unmap cow pages
     as well? If not, I am proposing changing it to not unmap cow pages.

     I noticed this while while writing virtio_fs code where when I tried
     to reclaim a memory range and that corrupted the executable and I
     was running from virtio-fs and program got segment violation."

Dan:

    "In fact the unmap_mapping_range() in this path is only to synchronize
     against get_user_pages_fast() and force it to call back into the
     filesystem to re-establish the mapping. COW pages should be left
     untouched by dax_layout_busy_page()."

Cc: <stable@vger.kernel.org>
Fixes: 5fac7408 ("mm, fs, dax: handle layout changes to pinned dax mappings")
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20190802192956.GA3032@redhat.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The condition checking whether put_unlocked_entry() needs to wake up
following waiter got broken by commit 23c84eb7 ("dax: Fix missed
wakeup with PMD faults"). We need to wake the waiter whenever the passed
entry is valid (i.e., non-NULL and not special conflict entry). This
could lead to processes never being woken up when waiting for entry
lock. Fix the condition.

Cc: <stable@vger.kernel.org>
Link: http://lore.kernel.org/r/20190729120228.GC17833@quack2.suse.cz


Fixes: 23c84eb7 ("dax: Fix missed wakeup with PMD faults")
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Move internal function declarations out of fs/internal.h into
include/linux/iomap.h so that our transition is complete.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

RocksDB can hang indefinitely when using a DAX file.  This is due to
a bug in the XArray conversion when handling a PMD fault and finding a
PTE entry.  We use the wrong index in the hash and end up waiting on
the wrong waitqueue.

There's actually no need to wait; if we find a PTE entry while looking
for a PMD entry, we can return immediately as we know we should fall
back to a PTE fault (which may not conflict with the lock held).

We reuse the XA_RETRY_ENTRY to signal a conflicting entry was found.
This value can never be found in an XArray while holding its lock, so
it does not create an ambiguity.

Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/CAPcyv4hwHpX-MkUEqxwdTj7wCCZCN4RV-L4jsnuwLGyL_UEG4A@mail.gmail.com


Fixes: b15cd800 ("dax: Convert page fault handlers to XArray")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Robert Barror <robert.barror@intel.com>
Reported-by: Seema Pandit <seema.pandit@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

All callers of lockdep_assert_held_exclusive() use it to verify the
correct locking state of either a semaphore (ldisc_sem in tty,
mmap_sem for perf events, i_rwsem of inode for dax) or rwlock by
apparmor. Thus it makes sense to rename _exclusive to _write since
that's the semantics callers care. Additionally there is already
lockdep_assert_held_read(), which this new naming is more consistent with.

No functional changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190531100651.3969-1-nborisov@suse.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

When inserting entry into xarray, we store mapping and index in
corresponding struct pages for memory error handling. When it happened
that one process was mapping file at PMD granularity while another
process at PTE granularity, we could wrongly deassociate PMD range and
then reassociate PTE range leaving the rest of struct pages in PMD range
without mapping information which could later cause missed notifications
about memory errors. Fix the problem by calling the association /
deassociation code if and only if we are really going to update the
xarray (deassociating and associating zero or empty entries is just
no-op so there's no reason to complicate the code with trying to avoid
the calls for these cases).

Cc: <stable@vger.kernel.org>
Fixes: d2c997c0 ("fs, dax: use page->mapping to warn if truncate...")
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>