linux-toradex.git/mm/truncate.c, branch v4.16-rc4

mm: add unmap_mapping_pages()

2018-02-01T01:18:37+00:00

Several users of unmap_mapping_range() would prefer to express their
range in pages rather than bytes.  Unfortuately, on a 32-bit kernel, you
have to remember to cast your page number to a 64-bit type before
shifting it, and four places in the current tree didn't remember to do
that.  That's a sign of a bad interface.

Conveniently, unmap_mapping_range() actually converts from bytes into
pages, so hoist the guts of unmap_mapping_range() into a new function
unmap_mapping_pages() and convert the callers which want to use pages.

Link: http://lkml.kernel.org/r/20171206142627.GD32044@bombadil.infradead.org
Signed-off-by: Matthew Wilcox 
Reported-by: "zhangyi (F)" 
Reviewed-by: Ross Zwisler 
Acked-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, pagevec: remove cold parameter for pagevecs

2017-11-16T02:21:06+00:00

Every pagevec_init user claims the pages being released are hot even in
cases where it is unlikely the pages are hot.  As no one cares about the
hotness of pages being released to the allocator, just ditch the
parameter.

No performance impact is expected as the overhead is marginal.  The
parameter is removed simply because it is a bit stupid to have a useless
parameter copied everywhere.

Link: http://lkml.kernel.org/r/20171018075952.10627-6-mgorman@techsingularity.net
Signed-off-by: Mel Gorman 
Acked-by: Vlastimil Babka 
Cc: Andi Kleen 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Jan Kara 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, truncate: remove all exceptional entries from pagevec under one lock

2017-11-16T02:21:06+00:00

During truncate each entry in a pagevec is checked to see if it is an
exceptional entry and if so, the shadow entry is cleaned up.  This is
potentially expensive as multiple entries for a mapping locks/unlocks
the tree lock.  This batches the operation such that any exceptional
entries removed from a pagevec only acquire the mapping tree lock once.
The corner case where this is more expensive is where there is only one
exceptional entry but this is unlikely due to temporal locality and how
it affects LRU ordering.  Note that for truncations of small files
created recently, this patch should show no gain because it only batches
the handling of exceptional entries.

sparsetruncate (large)
                              4.14.0-rc4             4.14.0-rc4
                         pickhelper-v1r1       batchshadow-v1r1
Min          Time       38.00 (   0.00%)       27.00 (  28.95%)
1st-qrtle    Time       40.00 (   0.00%)       28.00 (  30.00%)
2nd-qrtle    Time       44.00 (   0.00%)       41.00 (   6.82%)
3rd-qrtle    Time      146.00 (   0.00%)      147.00 (  -0.68%)
Max-90%      Time      153.00 (   0.00%)      153.00 (   0.00%)
Max-95%      Time      155.00 (   0.00%)      156.00 (  -0.65%)
Max-99%      Time      181.00 (   0.00%)      171.00 (   5.52%)
Amean        Time       93.04 (   0.00%)       88.43 (   4.96%)
Best99%Amean Time       92.08 (   0.00%)       86.13 (   6.46%)
Best95%Amean Time       89.19 (   0.00%)       83.13 (   6.80%)
Best90%Amean Time       85.60 (   0.00%)       79.15 (   7.53%)
Best75%Amean Time       72.95 (   0.00%)       65.09 (  10.78%)
Best50%Amean Time       39.86 (   0.00%)       28.20 (  29.25%)
Best25%Amean Time       39.44 (   0.00%)       27.70 (  29.77%)

bonnie
                                      4.14.0-rc4             4.14.0-rc4
                                 pickhelper-v1r1       batchshadow-v1r1
Hmean     SeqCreate ops         71.92 (   0.00%)       76.78 (   6.76%)
Hmean     SeqCreate read        42.42 (   0.00%)       45.01 (   6.10%)
Hmean     SeqCreate del      26519.88 (   0.00%)    27191.87 (   2.53%)
Hmean     RandCreate ops        71.92 (   0.00%)       76.95 (   7.00%)
Hmean     RandCreate read       44.44 (   0.00%)       49.23 (  10.78%)
Hmean     RandCreate del     24948.62 (   0.00%)    24764.97 (  -0.74%)

Truncation of a large number of files shows a substantial gain with 99%
of files being truncated 6.46% faster.  bonnie shows a modest gain of
2.53%

[jack@suse.cz: fix truncate_exceptional_pvec_entries()]
  Link: http://lkml.kernel.org/r/20171108164226.26788-1-jack@suse.cz
Link: http://lkml.kernel.org/r/20171018075952.10627-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman 
Signed-off-by: Jan Kara 
Reviewed-by: Jan Kara 
Acked-by: Johannes Weiner 
Cc: Andi Kleen 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, truncate: do not check mapping for every page being truncated

2017-11-16T02:21:06+00:00

During truncation, the mapping has already been checked for shmem and
dax so it's known that workingset_update_node is required.

This patch avoids the checks on mapping for each page being truncated.
In all other cases, a lookup helper is used to determine if
workingset_update_node() needs to be called.  The one danger is that the
API is slightly harder to use as calling workingset_update_node directly
without checking for dax or shmem mappings could lead to surprises.
However, the API rarely needs to be used and hopefully the comment is
enough to give people the hint.

sparsetruncate (tiny)
                              4.14.0-rc4             4.14.0-rc4
                             oneirq-v1r1        pickhelper-v1r1
Min          Time      141.00 (   0.00%)      140.00 (   0.71%)
1st-qrtle    Time      142.00 (   0.00%)      141.00 (   0.70%)
2nd-qrtle    Time      142.00 (   0.00%)      142.00 (   0.00%)
3rd-qrtle    Time      143.00 (   0.00%)      143.00 (   0.00%)
Max-90%      Time      144.00 (   0.00%)      144.00 (   0.00%)
Max-95%      Time      147.00 (   0.00%)      145.00 (   1.36%)
Max-99%      Time      195.00 (   0.00%)      191.00 (   2.05%)
Max          Time      230.00 (   0.00%)      205.00 (  10.87%)
Amean        Time      144.37 (   0.00%)      143.82 (   0.38%)
Stddev       Time       10.44 (   0.00%)        9.00 (  13.74%)
Coeff        Time        7.23 (   0.00%)        6.26 (  13.41%)
Best99%Amean Time      143.72 (   0.00%)      143.34 (   0.26%)
Best95%Amean Time      142.37 (   0.00%)      142.00 (   0.26%)
Best90%Amean Time      142.19 (   0.00%)      141.85 (   0.24%)
Best75%Amean Time      141.92 (   0.00%)      141.58 (   0.24%)
Best50%Amean Time      141.69 (   0.00%)      141.31 (   0.27%)
Best25%Amean Time      141.38 (   0.00%)      140.97 (   0.29%)

As you'd expect, the gain is marginal but it can be detected.  The
differences in bonnie are all within the noise which is not surprising
given the impact on the microbenchmark.

radix_tree_update_node_t is a callback for some radix operations that
optionally passes in a private field.  The only user of the callback is
workingset_update_node and as it no longer requires a mapping, the
private field is removed.

Link: http://lkml.kernel.org/r/20171018075952.10627-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman 
Acked-by: Johannes Weiner 
Reviewed-by: Jan Kara 
Cc: Andi Kleen 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: batch radix tree operations when truncating pages

2017-11-16T02:21:06+00:00

Currently we remove pages from the radix tree one by one.  To speed up
page cache truncation, lock several pages at once and free them in one
go.  This allows us to batch radix tree operations in a more efficient
way and also save round-trips on mapping->tree_lock.  As a result we
gain about 20% speed improvement in page cache truncation.

Data from a simple benchmark timing 10000 truncates of 1024 pages (on
ext4 on ramdisk but the filesystem is barely visible in the profiles).
The range shows 1% and 95% percentiles of the measured times:

  4.14-rc2	4.14-rc2 + batched truncation
  248-256	209-219
  249-258	209-217
  248-255	211-239
  248-255	209-217
  247-256	210-218

[jack@suse.cz: convert delete_from_page_cache_batch() to pagevec]
  Link: http://lkml.kernel.org/r/20171018111648.13714-1-jack@suse.cz
[akpm@linux-foundation.org: move struct pagevec forward declaration to top-of-file]
Link: http://lkml.kernel.org/r/20171010151937.26984-8-jack@suse.cz
Signed-off-by: Jan Kara 
Acked-by: Mel Gorman 
Reviewed-by: Andi Kleen 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: refactor truncate_complete_page()

2017-11-16T02:21:06+00:00

Move call of delete_from_page_cache() and page->mapping check out of
truncate_complete_page() into the single caller - truncate_inode_page().
Also move page_mapped() check into truncate_complete_page().  That way
it will be easier to batch operations.

Also rename truncate_complete_page() to truncate_cleanup_page().

Link: http://lkml.kernel.org/r/20171010151937.26984-3-jack@suse.cz
Signed-off-by: Jan Kara 
Acked-by: Mel Gorman 
Reviewed-by: Andi Kleen 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/truncate.c: fix THP handling in invalidate_mapping_pages()

2017-07-10T23:32:32+00:00

The condition checking for THP straddling end of invalidated range is
wrong - it checks 'index' against 'end' but 'index' has been already
advanced to point to the end of THP and thus the condition can never be
true.  As a result THP straddling 'end' has been fully invalidated.
Given the nature of invalidate_mapping_pages(), this could be only
performance issue.  In fact, we are lucky the condition is wrong because
if it was ever true, we'd leave locked page behind.

Fix the condition checking for THP straddling 'end' and also properly
unlock the page.  Also update the comment before the condition to
explain why we decide not to invalidate the page as it was not clear to
me and I had to ask Kirill.

Link: http://lkml.kernel.org/r/20170619124723.21656-1-jack@suse.cz
Signed-off-by: Jan Kara 
Acked-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: fix data corruption due to stale mmap reads

2017-05-12T22:57:15+00:00

Currently, we didn't invalidate page tables during invalidate_inode_pages2()
for DAX.  That could result in e.g. 2MiB zero page being mapped into
page tables while there were already underlying blocks allocated and
thus data seen through mmap were different from data seen by read(2).
The following sequence reproduces the problem:

 - open an mmap over a 2MiB hole

 - read from a 2MiB hole, faulting in a 2MiB zero page

 - write to the hole with write(3p). The write succeeds but we
   incorrectly leave the 2MiB zero page mapping intact.

 - via the mmap, read the data that was just written. Since the zero
   page mapping is still intact we read back zeroes instead of the new
   data.

Fix the problem by unconditionally calling invalidate_inode_pages2_range()
in dax_iomap_actor() for new block allocations and by properly
invalidating page tables in invalidate_inode_pages2_range() for DAX
mappings.

Fixes: c6dcf52c23d2d3fb5235cec42d7dd3f786b87d55
Link: http://lkml.kernel.org/r/20170510085419.27601-3-jack@suse.cz
Signed-off-by: Jan Kara 
Signed-off-by: Ross Zwisler 
Cc: Dan Williams 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

dax: prevent invalidation of mapped DAX entries

2017-05-12T22:57:15+00:00

Patch series "mm,dax: Fix data corruption due to mmap inconsistency",
v4.

This series fixes data corruption that can happen for DAX mounts when
page faults race with write(2) and as a result page tables get out of
sync with block mappings in the filesystem and thus data seen through
mmap is different from data seen through read(2).

The series passes testing with t_mmap_stale test program from Ross and
also other mmap related tests on DAX filesystem.

This patch (of 4):

dax_invalidate_mapping_entry() currently removes DAX exceptional entries
only if they are clean and unlocked.  This is done via:

  invalidate_mapping_pages()
    invalidate_exceptional_entry()
      dax_invalidate_mapping_entry()

However, for page cache pages removed in invalidate_mapping_pages()
there is an additional criteria which is that the page must not be
mapped.  This is noted in the comments above invalidate_mapping_pages()
and is checked in invalidate_inode_page().

For DAX entries this means that we can can end up in a situation where a
DAX exceptional entry, either a huge zero page or a regular DAX entry,
could end up mapped but without an associated radix tree entry.  This is
inconsistent with the rest of the DAX code and with what happens in the
page cache case.

We aren't able to unmap the DAX exceptional entry because according to
its comments invalidate_mapping_pages() isn't allowed to block, and
unmap_mapping_range() takes a write lock on the mapping->i_mmap_rwsem.

Since we essentially never have unmapped DAX entries to evict from the
radix tree, just remove dax_invalidate_mapping_entry().

Fixes: c6dcf52c23d2 ("mm: Invalidate DAX radix tree entries only if appropriate")
Link: http://lkml.kernel.org/r/20170510085419.27601-2-jack@suse.cz
Signed-off-by: Ross Zwisler 
Signed-off-by: Jan Kara 
Reported-by: Jan Kara 
Cc: Dan Williams 
Cc:     [4.10+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/truncate: avoid pointless cleancache_invalidate_inode() calls.

2017-05-03T22:52:12+00:00

cleancache_invalidate_inode() called truncate_inode_pages_range() and
invalidate_inode_pages2_range() twice - on entry and on exit.  It's
stupid and waste of time.  It's enough to call it once at exit.

Link: http://lkml.kernel.org/r/20170424164135.22350-5-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin 
Reviewed-by: Jan Kara 
Acked-by: Konrad Rzeszutek Wilk 
Cc: Alexander Viro 
Cc: Ross Zwisler 
Cc: Jens Axboe 
Cc: Johannes Weiner 
Cc: Alexey Kuznetsov 
Cc: Christoph Hellwig 
Cc: Nikolay Borisov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds