linux.git/mm/readahead.c, branch v4.18

mm: split ->readpages calls to avoid non-contiguous pages lists

2018-06-02T01:37:32+00:00

That way file systems don't have to go spotting for non-contiguous pages
and work around them.  It also kicks off I/O earlier, allowing it to
finish earlier and reduce latency.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Dave Chinner 
Reviewed-by: Darrick J. Wong 
Signed-off-by: Darrick J. Wong

mm: return an unsigned int from __do_page_cache_readahead

2018-06-02T01:37:32+00:00

We never return an error, so switch to returning an unsigned int.  Most
callers already did implicit casts to an unsigned type, and the one that
didn't can be simplified now.

Suggested-by: Matthew Wilcox 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Dave Chinner 
Reviewed-by: Darrick J. Wong 
Signed-off-by: Darrick J. Wong

mm: give the 'ret' variable a better name __do_page_cache_readahead

2018-06-02T01:37:32+00:00

It counts the number of pages acted on, so name it nr_pages to make that
obvious.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Dave Chinner 
Reviewed-by: Darrick J. Wong 
Signed-off-by: Darrick J. Wong

page cache: use xa_lock

2018-04-11T17:28:39+00:00

Remove the address_space ->tree_lock and use the xa_lock newly added to
the radix_tree_root.  Rename the address_space ->page_tree to ->i_pages,
since we don't really care that it's a tree.

[willy@infradead.org: fix nds32, fs/dax.c]
  Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Acked-by: Jeff Layton 
Cc: Darrick J. Wong 
Cc: Dave Chinner 
Cc: Ryusuke Konishi 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: add ksys_readahead() helper; remove in-kernel calls to sys_readahead()

2018-04-02T18:16:12+00:00

Using this helper allows us to avoid the in-kernel calls to the
sys_readahead() syscall. The ksys_ prefix denotes that this function is
meant as a drop-in replacement for the syscall. In particular, it uses the
same calling convention as sys_readahead().

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Andrew Morton 
Cc: linux-mm@kvack.org
Signed-off-by: Dominik Brodowski

mm: don't cap request size based on read-ahead setting

2016-12-13T02:55:08+00:00

We ran into a funky issue, where someone doing 256K buffered reads saw
128K requests at the device level.  Turns out it is read-ahead capping
the request size, since we use 128K as the default setting.  This
doesn't make a lot of sense - if someone is issuing 256K reads, they
should see 256K reads, regardless of the read-ahead setting, if the
underlying device can support a 256K read in a single command.

This patch introduces a bdi hint, io_pages.  This is the soft max IO
size for the lower level, I've hooked it up to the bdev settings here.
Read-ahead is modified to issue the maximum of the user request size,
and the read-ahead max size, but capped to the max request size on the
device side.  The latter is done to avoid reading ahead too much, if the
application asks for a huge read.  With this patch, the kernel behaves
like the application expects.

Link: http://lkml.kernel.org/r/1479498073-8657-1-git-send-email-axboe@fb.com
Signed-off-by: Jens Axboe 
Acked-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: silently skip readahead for DAX inodes

2016-08-27T00:39:35+00:00

For DAX inodes we need to be careful to never have page cache pages in
the mapping->page_tree.  This radix tree should be composed only of DAX
exceptional entries and zero pages.

ltp's readahead02 test was triggering a warning because we were trying
to insert a DAX exceptional entry but found that a page cache page had
already been inserted into the tree.  This page was being inserted into
the radix tree in response to a readahead(2) call.

Readahead doesn't make sense for DAX inodes, but we don't want it to
report a failure either.  Instead, we just return success and don't do
any work.

Link: http://lkml.kernel.org/r/20160824221429.21158-1-ross.zwisler@linux.intel.com
Signed-off-by: Ross Zwisler 
Reported-by: Jeff Moyer 
Cc: Dan Williams 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Jan Kara 
Cc: 	[4.5+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, memcg: use consistent gfp flags during readahead

2016-07-26T23:19:19+00:00

Vladimir has noticed that we might declare memcg oom even during
readahead because read_pages only uses GFP_KERNEL (with mapping_gfp
restriction) while __do_page_cache_readahead uses
page_cache_alloc_readahead which adds __GFP_NORETRY to prevent from
OOMs.  This gfp mask discrepancy is really unfortunate and easily
fixable.  Drop page_cache_alloc_readahead() which only has one user and
outsource the gfp_mask logic into readahead_gfp_mask and propagate this
mask from __do_page_cache_readahead down to read_pages.

This alone would have only very limited impact as most filesystems are
implementing ->readpages and the common implementation mpage_readpages
does GFP_KERNEL (with mapping_gfp restriction) again.  We can tell it to
use readahead_gfp_mask instead as this function is called only during
readahead as well.  The same applies to read_cache_pages.

ext4 has its own ext4_mpage_readpages but the path which has pages !=
NULL can use the same gfp mask.  Btrfs, cifs, f2fs and orangefs are
doing a very similar pattern to mpage_readpages so the same can be
applied to them as well.

[akpm@linux-foundation.org: coding-style fixes]
[mhocko@suse.com: restrict gfp mask in mpage_alloc]
  Link: http://lkml.kernel.org/r/20160610074223.GC32285@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/1465301556-26431-1-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Cc: Vladimir Davydov 
Cc: Chris Mason 
Cc: Steve French 
Cc: Theodore Ts'o 
Cc: Jan Kara 
Cc: Mike Marshall 
Cc: Jaegeuk Kim 
Cc: Changman Lee 
Cc: Chao Yu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros

2016-04-04T17:41:08+00:00

PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
ago with promise that one day it will be possible to implement page
cache with bigger chunks than PAGE_SIZE.

This promise never materialized.  And unlikely will.

We have many places where PAGE_CACHE_SIZE assumed to be equal to
PAGE_SIZE.  And it's constant source of confusion on whether
PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
especially on the border between fs and mm.

Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
breakage to be doable.

Let's stop pretending that pages in page cache are special.  They are
not.

The changes are pretty straight-forward:

 -  << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> ;

 -  >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> ;

 - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};

 - page_cache_get() -> get_page();

 - page_cache_release() -> put_page();

This patch contains automated changes generated with coccinelle using
script below.  For some reason, coccinelle doesn't patch header files.
I've called spatch for them manually.

The only adjustment after coccinelle is revert of changes to
PAGE_CAHCE_ALIGN definition: we are going to drop it later.

There are few places in the code where coccinelle didn't reach.  I'll
fix them manually in a separate patch.  Comments and documentation also
will be addressed with the separate patch.

virtual patch

@@
expression E;
@@
- E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E

@@
expression E;
@@
- E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E

@@
@@
- PAGE_CACHE_SHIFT
+ PAGE_SHIFT

@@
@@
- PAGE_CACHE_SIZE
+ PAGE_SIZE

@@
@@
- PAGE_CACHE_MASK
+ PAGE_MASK

@@
expression E;
@@
- PAGE_CACHE_ALIGN(E)
+ PAGE_ALIGN(E)

@@
expression E;
@@
- page_cache_get(E)
+ get_page(E)

@@
expression E;
@@
- page_cache_release(E)
+ put_page(E)

Signed-off-by: Kirill A. Shutemov 
Acked-by: Michal Hocko 
Signed-off-by: Linus Torvalds

mm: move lru_to_page to mm_inline.h

2016-01-15T00:00:49+00:00

Move lru_to_page() from internal.h to mm_inline.h.

Signed-off-by: Geliang Tang 
Acked-by: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds