linux-toradex.git/mm/readahead.c, branch v5.12

mm: use limited read-ahead to satisfy read

2020-10-17T19:49:08+00:00

For the case where read-ahead is disabled on the file, or if the cgroup
is congested, ensure that we can at least do 1 page of read-ahead to
make progress on the read in an async fashion. This could potentially be
larger, but it's not needed in terms of functionality, so let's error on
the side of caution as larger counts of pages may run into reclaim
issues (particularly if we're congested).

This makes sure we're not hitting the potentially sync ->readpage() path
for IO that is marked IOCB_WAITQ, which could cause us to block. It also
means we'll use the same path for IO, regardless of whether or not
read-ahead happens to be disabled on the lower level device.

Acked-by: Johannes Weiner 
Reported-by: Matthew Wilcox (Oracle) 
Reported-by: Hao_Xu 
[axboe: updated for new ractl API]
Signed-off-by: Jens Axboe

mm/readahead: pass a file_ra_state into force_page_cache_ra

2020-10-16T18:11:16+00:00

The file_ra_state being passed into page_cache_sync_readahead() was being
ignored in favour of using the one embedded in the struct file.  The only
caller for which this makes a difference is the fsverity code if the file
has been marked as POSIX_FADV_RANDOM, but it's confusing and worth fixing.

Signed-off-by: David Howells 
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: Eric Biggers 
Link: https://lkml.kernel.org/r/20200903140844.14194-10-willy@infradead.org
Signed-off-by: Linus Torvalds

mm/readahead: add page_cache_sync_ra and page_cache_async_ra

2020-10-16T18:11:16+00:00

Reimplement page_cache_sync_readahead() and page_cache_async_readahead()
as wrappers around versions of the function which take a readahead_control
in preparation for making do_sync_mmap_readahead() pass down an RAC
struct.

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: David Howells 
Cc: Eric Biggers 
Link: https://lkml.kernel.org/r/20200903140844.14194-8-willy@infradead.org
Signed-off-by: Linus Torvalds

mm/readahead: pass readahead_control to force_page_cache_ra

2020-10-16T18:11:16+00:00

Reimplement force_page_cache_readahead() as a wrapper around
force_page_cache_ra().  Pass the existing readahead_control from
page_cache_sync_readahead().

Signed-off-by: David Howells 
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: Eric Biggers 
Link: https://lkml.kernel.org/r/20200903140844.14194-7-willy@infradead.org
Signed-off-by: Linus Torvalds

mm/readahead: make ondemand_readahead take a readahead_control

2020-10-16T18:11:16+00:00

Make ondemand_readahead() take a readahead_control struct in preparation
for making do_sync_mmap_readahead() pass down an RAC struct.

Signed-off-by: David Howells 
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: Eric Biggers 
Link: https://lkml.kernel.org/r/20200903140844.14194-6-willy@infradead.org
Signed-off-by: Linus Torvalds

mm/readahead: make do_page_cache_ra take a readahead_control

2020-10-16T18:11:16+00:00

Rename __do_page_cache_readahead() to do_page_cache_ra() and call it
directly from ondemand_readahead() instead of indirecting via ra_submit().

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: David Howells 
Cc: Eric Biggers 
Link: https://lkml.kernel.org/r/20200903140844.14194-5-willy@infradead.org
Signed-off-by: Linus Torvalds

mm/readahead: make page_cache_ra_unbounded take a readahead_control

2020-10-16T18:11:16+00:00

Define it in the callers instead of in page_cache_ra_unbounded().

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: David Howells 
Cc: Eric Biggers 
Link: https://lkml.kernel.org/r/20200903140844.14194-4-willy@infradead.org
Signed-off-by: Linus Torvalds

mm/readahead: add DEFINE_READAHEAD

2020-10-16T18:11:15+00:00

Patch series "Readahead patches for 5.9/5.10".

These are infrastructure for both the THP patchset and for the fscache
rewrite,

For both pieces of infrastructure being build on top of this patchset, we
want the ractl to be available higher in the call-stack.

For David's work, he wants to add the 'critical page' to the ractl so that
he knows which page NEEDS to be brought in from storage, and which ones
are nice-to-have.  We might want something similar in block storage too.
It used to be simple -- the first page was the critical one, but then mmap
added fault-around and so for that usecase, the middle page is the
critical one.  Anyway, I don't have any code to show that yet, we just
know that the lowest point in the callchain where we have that information
is do_sync_mmap_readahead() and so the ractl needs to start its life
there.

For THP, we havew the code that needs it.  It's actually the apex patch to
the series; the one which finally starts to allocate THPs and present them
to consenting filesystems:
http://git.infradead.org/users/willy/pagecache.git/commitdiff/798bcf30ab2eff278caad03a9edca74d2f8ae760

This patch (of 8):

Allow for a more concise definition of a struct readahead_control.

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: Eric Biggers 
Cc: David Howells 
Link: https://lkml.kernel.org/r/20200903140844.14194-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20200903140844.14194-3-willy@infradead.org
Signed-off-by: Linus Torvalds

mm: use memalloc_nofs_save in readahead path

2020-06-02T17:59:07+00:00

Ensure that memory allocations in the readahead path do not attempt to
reclaim file-backed pages, which could lead to a deadlock.  It is
possible, though unlikely this is the root cause of a problem observed
by Cong Wang.

Reported-by: Cong Wang 
Suggested-by: Michal Hocko 
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Reviewed-by: William Kucharski 
Cc: Chao Yu 
Cc: Christoph Hellwig 
Cc: Darrick J. Wong 
Cc: Dave Chinner 
Cc: Eric Biggers 
Cc: Gao Xiang 
Cc: Jaegeuk Kim 
Cc: John Hubbard 
Cc: Joseph Qi 
Cc: Junxiao Bi 
Cc: Zi Yan 
Cc: Johannes Thumshirn 
Cc: Miklos Szeredi 
Link: http://lkml.kernel.org/r/20200414150233.24495-16-willy@infradead.org
Signed-off-by: Linus Torvalds

mm: document why we don't set PageReadahead

2020-06-02T17:59:07+00:00

If the page is already in cache, we don't set PageReadahead on it.

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Reviewed-by: Christoph Hellwig 
Reviewed-by: William Kucharski 
Cc: Chao Yu 
Cc: Cong Wang 
Cc: Darrick J. Wong 
Cc: Dave Chinner 
Cc: Eric Biggers 
Cc: Gao Xiang 
Cc: Jaegeuk Kim 
Cc: John Hubbard 
Cc: Joseph Qi 
Cc: Junxiao Bi 
Cc: Michal Hocko 
Cc: Zi Yan 
Cc: Johannes Thumshirn 
Cc: Miklos Szeredi 
Link: http://lkml.kernel.org/r/20200414150233.24495-15-willy@infradead.org
Signed-off-by: Linus Torvalds