linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Michal Hocko <mhocko@kernel.org>
To: Jiri Kosina <jikos@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-api@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Jann Horn <jannh@google.com>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Dave Chinner <david@fromorbit.com>,
	Kevin Easton <kevin@guarana.org>,
	Matthew Wilcox <willy@infradead.org>,
	Cyril Hrubis <chrubis@suse.cz>, Tejun Heo <tj@kernel.org>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Daniel Gruss <daniel@gruss.cc>,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 2/3] mm/filemap: initiate readahead even if IOCB_NOWAIT is set for the I/O
Date: Thu, 31 Jan 2019 12:32:23 +0100	[thread overview]
Message-ID: <20190131113223.GU18811@dhcp22.suse.cz> (raw)
In-Reply-To: <nycvar.YFH.7.76.1901311129420.3281@cbobk.fhfr.pm>

On Thu 31-01-19 11:30:24, Jiri Kosina wrote:
> On Thu, 31 Jan 2019, Michal Hocko wrote:
> 
> > > > > diff --git a/mm/filemap.c b/mm/filemap.c
> > > > > index 9f5e323e883e..7bcdd36e629d 100644
> > > > > --- a/mm/filemap.c
> > > > > +++ b/mm/filemap.c
> > > > > @@ -2075,8 +2075,6 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
> > > > >  
> > > > >  		page = find_get_page(mapping, index);
> > > > >  		if (!page) {
> > > > > -			if (iocb->ki_flags & IOCB_NOWAIT)
> > > > > -				goto would_block;
> > > > >  			page_cache_sync_readahead(mapping,
> > > > >  					ra, filp,
> > > > >  					index, last_index - index);
> > > > 
> > > > Maybe a stupid question but I am not really familiar with this path but
> > > > what exactly does prevent a sync read down page_cache_sync_readahead
> > > > path?
> > > 
> > > page_cache_sync_readahead() only submits the read ahead request(s), it 
> > > doesn't wait for it to finish.
> > 
> > OK, I guess my question was not precise. What does prevent taking fs
> > locks down the path?
> 
> Well, RWF_NOWAIT doesn't mean the kernel can't reschedule while executing 
> preadv2(), right? It just means it will not wait for the arrival of the 
> whole data blob into pagecache in case it's not there.

No, it can reschedule for sure but the man page says: 
: If this flag is specified, the preadv2() system call will return
: instantly if it would have to read data from the backing storage or wait
: for a lock.

I assume that the lock is meant to be a filesystem lock here.
-- 
Michal Hocko
SUSE Labs


  reply	other threads:[~2019-01-31 11:32 UTC|newest]

Thread overview: 215+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-05 17:27 [PATCH] mm/mincore: allow for making sys_mincore() privileged Jiri Kosina
2019-01-05 17:27 ` Jiri Kosina
2019-01-05 19:14 ` Vlastimil Babka
2019-01-05 19:24   ` Jiri Kosina
2019-01-05 19:24     ` Jiri Kosina
2019-01-05 19:38     ` Vlastimil Babka
2019-01-08  9:14       ` Bernd Petrovitsch
2019-01-08 11:37         ` Jiri Kosina
2019-01-08 11:37           ` Jiri Kosina
2019-01-08 13:53           ` Bernd Petrovitsch
2019-01-08 14:08             ` Kirill A. Shutemov
2019-01-05 19:44 ` kbuild test robot
2019-01-05 19:46 ` Linus Torvalds
2019-01-05 19:46   ` Linus Torvalds
2019-01-05 20:12   ` Jiri Kosina
2019-01-05 20:12     ` Jiri Kosina
2019-01-05 20:17     ` Linus Torvalds
2019-01-05 20:17       ` Linus Torvalds
2019-01-05 20:43       ` Jiri Kosina
2019-01-05 20:43         ` Jiri Kosina
2019-01-05 21:54         ` Linus Torvalds
2019-01-05 21:54           ` Linus Torvalds
2019-01-06 11:33           ` Kevin Easton
2019-01-08  8:50           ` Kevin Easton
2019-01-18 14:23           ` Tejun Heo
2019-01-05 20:13   ` Linus Torvalds
2019-01-05 20:13     ` Linus Torvalds
2019-01-05 19:56 ` kbuild test robot
2019-01-05 22:54 ` Jann Horn
2019-01-05 22:54   ` Jann Horn
2019-01-05 23:05   ` Linus Torvalds
2019-01-05 23:05     ` Linus Torvalds
2019-01-05 23:16     ` Linus Torvalds
2019-01-05 23:16       ` Linus Torvalds
2019-01-05 23:28       ` Linus Torvalds
2019-01-05 23:28         ` Linus Torvalds
2019-01-05 23:39       ` Linus Torvalds
2019-01-05 23:39         ` Linus Torvalds
2019-01-06  0:11         ` Matthew Wilcox
2019-01-06  0:22           ` Linus Torvalds
2019-01-06  0:22             ` Linus Torvalds
2019-01-06  1:50             ` Linus Torvalds
2019-01-06  1:50               ` Linus Torvalds
2019-01-06 21:46               ` Linus Torvalds
2019-01-06 21:46                 ` Linus Torvalds
2019-01-08  4:43                 ` Dave Chinner
2019-01-08 17:57                   ` Linus Torvalds
2019-01-08 17:57                     ` Linus Torvalds
2019-01-09  2:24                     ` Dave Chinner
2019-01-09  2:31                       ` Jiri Kosina
2019-01-09  2:31                         ` Jiri Kosina
2019-01-09  4:39                         ` Dave Chinner
2019-01-09 10:08                           ` Jiri Kosina
2019-01-09 10:08                             ` Jiri Kosina
2019-01-10  1:15                             ` Dave Chinner
2019-01-10  7:54                               ` Jiri Kosina
2019-01-10  7:54                                 ` Jiri Kosina
2019-01-09 18:25                           ` Linus Torvalds
2019-01-09 18:25                             ` Linus Torvalds
2019-01-10  0:44                             ` Dave Chinner
2019-01-10  1:18                               ` Linus Torvalds
2019-01-10  1:18                                 ` Linus Torvalds
2019-01-10  5:26                                 ` Andy Lutomirski
2019-01-10  5:26                                   ` Andy Lutomirski
2019-01-10 14:47                                   ` Matthew Wilcox
2019-01-10 21:44                                     ` Dave Chinner
2019-01-10 21:59                                       ` Linus Torvalds
2019-01-10 21:59                                         ` Linus Torvalds
2019-01-11  1:47                                   ` Dave Chinner
2019-01-10  7:03                                 ` Dave Chinner
2019-01-10 11:47                                   ` Linus Torvalds
2019-01-10 11:47                                     ` Linus Torvalds
2019-01-10 12:24                                     ` Dominique Martinet
2019-01-10 12:24                                       ` Dominique Martinet
2019-01-10 22:11                                       ` Linus Torvalds
2019-01-10 22:11                                         ` Linus Torvalds
2019-01-11  2:03                                         ` Dave Chinner
2019-01-11  2:18                                           ` Linus Torvalds
2019-01-11  2:18                                             ` Linus Torvalds
2019-01-11  4:04                                             ` Dave Chinner
2019-01-11  4:08                                               ` Andy Lutomirski
2019-01-11  7:20                                                 ` Dave Chinner
2019-01-11  7:08                                               ` Linus Torvalds
2019-01-11  7:08                                                 ` Linus Torvalds
2019-01-11  7:36                                                 ` Dave Chinner
2019-01-11 16:26                                                   ` Linus Torvalds
2019-01-11 16:26                                                     ` Linus Torvalds
2019-01-15 23:45                                                     ` Dave Chinner
2019-01-16  4:54                                                       ` Linus Torvalds
2019-01-16  4:54                                                         ` Linus Torvalds
2019-01-16  5:49                                                         ` Linus Torvalds
2019-01-16  5:49                                                           ` Linus Torvalds
2019-01-17  1:26                                                         ` Dave Chinner
2019-02-20 15:49                                                     ` Nicolai Stange
2019-01-11  4:57                                         ` Dominique Martinet
2019-01-11  7:11                                           ` Linus Torvalds
2019-01-11  7:11                                             ` Linus Torvalds
2019-01-11  7:32                                             ` Dominique Martinet
2019-01-16  0:42                                         ` Josh Snyder
2019-01-16  5:00                                           ` Linus Torvalds
2019-01-16  5:00                                             ` Linus Torvalds
2019-01-16  5:25                                             ` Andy Lutomirski
2019-01-16  5:34                                               ` Linus Torvalds
2019-01-16  5:34                                                 ` Linus Torvalds
2019-01-16  5:46                                                 ` Dominique Martinet
2019-01-16  5:58                                                   ` Linus Torvalds
2019-01-16  5:58                                                     ` Linus Torvalds
2019-01-16  6:34                                                     ` Dominique Martinet
2019-01-16  7:52                                                       ` Josh Snyder
2019-01-16  7:52                                                         ` Josh Snyder
2019-01-16 12:18                                                         ` Kevin Easton
2019-01-17 21:45                                                         ` Vlastimil Babka
2019-01-18  4:49                                                           ` Linus Torvalds
2019-01-18  4:49                                                             ` Linus Torvalds
2019-01-18 18:58                                                             ` Vlastimil Babka
2019-01-16 16:12                                                     ` Jiri Kosina
2019-01-16 16:12                                                       ` Jiri Kosina
2019-01-16 17:48                                                       ` Linus Torvalds
2019-01-16 17:48                                                         ` Linus Torvalds
2019-01-16 20:23                                                         ` Jiri Kosina
2019-01-16 20:23                                                           ` Jiri Kosina
2019-01-16 21:37                                                           ` Matthew Wilcox
2019-01-16 21:41                                                             ` Jiri Kosina
2019-01-16 21:41                                                               ` Jiri Kosina
2019-01-17  9:52                                                               ` Cyril Hrubis
2019-01-28 13:49                                                               ` Cyril Hrubis
2019-01-17  4:51                                                             ` Linus Torvalds
2019-01-17  4:51                                                               ` Linus Torvalds
2019-01-18  4:54                                                               ` Linus Torvalds
2019-01-18  4:54                                                                 ` Linus Torvalds
2019-01-17  1:49                                                           ` Dominique Martinet
2019-01-23 20:27                                                           ` Linus Torvalds
2019-01-23 20:27                                                             ` Linus Torvalds
2019-01-23 20:35                                                             ` Linus Torvalds
2019-01-23 20:35                                                               ` Linus Torvalds
2019-01-23 23:12                                                               ` Jiri Kosina
2019-01-23 23:12                                                                 ` Jiri Kosina
2019-01-24  0:20                                                                 ` Linus Torvalds
2019-01-24  0:20                                                                   ` Linus Torvalds
2019-01-24  0:24                                                             ` Dominique Martinet
2019-01-24 12:45                                                               ` Dominique Martinet
2019-01-24 14:25                                                                 ` Jiri Kosina
2019-01-24 14:25                                                                   ` Jiri Kosina
2019-01-27 22:35                                                                   ` Jiri Kosina
2019-01-27 22:35                                                                     ` Jiri Kosina
2019-01-28  0:05                                                                     ` Dominique Martinet
2019-01-29 23:52                                                                       ` Jiri Kosina
2019-01-30  9:09                                                                         ` Michal Hocko
2019-01-30 12:29                                                                           ` Jiri Kosina
2019-01-16 12:36                                             ` Matthew Wilcox
2019-01-10 14:50                               ` Matthew Wilcox
2019-01-11  7:36                               ` Jiri Kosina
2019-01-11  7:36                                 ` Jiri Kosina
2019-01-17  2:22                                 ` Dave Chinner
2019-01-17  8:18                                   ` Jiri Kosina
2019-01-17  8:18                                     ` Jiri Kosina
2019-01-17 21:06                                     ` Dave Chinner
2019-01-07  4:32             ` Dominique Martinet
2019-01-07 10:33               ` Vlastimil Babka
2019-01-07 11:08                 ` Dominique Martinet
2019-01-07 11:59                   ` Vlastimil Babka
2019-01-07 13:29                   ` Daniel Gruss
2019-01-07 10:10         ` Michael Ellerman
2019-01-05 23:09   ` Jiri Kosina
2019-01-05 23:09     ` Jiri Kosina
2019-01-30 12:44 ` [PATCH 0/3] mincore() and IOCB_NOWAIT adjustments Vlastimil Babka
2019-01-30 12:44   ` [PATCH 1/3] mm/mincore: make mincore() more conservative Vlastimil Babka
2019-01-31  9:43     ` Michal Hocko
2019-01-31  9:51       ` Dominique Martinet
2019-01-31 17:46       ` Josh Snyder
2019-02-01  8:56     ` Vlastimil Babka
2019-03-06 23:13     ` Andrew Morton
2019-03-07  0:01       ` Jiri Kosina
2019-03-07  0:40         ` Dominique Martinet
2019-03-07  5:46           ` Jiri Kosina
2019-01-30 12:44   ` [PATCH 2/3] mm/filemap: initiate readahead even if IOCB_NOWAIT is set for the I/O Vlastimil Babka
2019-01-30 15:04     ` Florian Weimer
2019-01-30 15:15       ` Jiri Kosina
2019-01-31 10:47         ` Florian Weimer
2019-01-31 11:34           ` Jiri Kosina
2019-01-31  9:56     ` Michal Hocko
2019-01-31 10:15       ` Jiri Kosina
2019-01-31 10:23         ` Michal Hocko
2019-01-31 10:30           ` Jiri Kosina
2019-01-31 11:32             ` Michal Hocko [this message]
2019-01-31 17:54           ` Linus Torvalds
2019-02-01  5:13             ` Dave Chinner
2019-02-01  7:05               ` Linus Torvalds
2019-02-01  7:21                 ` Linus Torvalds
2019-02-01  1:44       ` Dave Chinner
2019-02-12 15:48         ` Jiri Kosina
2019-01-31 12:04     ` Daniel Gruss
2019-01-31 12:06       ` Vlastimil Babka
2019-01-31 12:08       ` Jiri Kosina
2019-01-31 12:57         ` Daniel Gruss
2019-01-30 12:44   ` [PATCH 3/3] mm/mincore: provide mapped status when cached status is not allowed Vlastimil Babka
2019-01-31 10:09     ` Michal Hocko
2019-02-01  9:04       ` Vlastimil Babka
2019-02-01  9:11         ` Michal Hocko
2019-02-01  9:27           ` Vlastimil Babka
2019-02-06 20:14             ` Jiri Kosina
2019-02-12  3:44         ` Jiri Kosina
2019-02-12  6:36           ` Michal Hocko
2019-02-12 13:09             ` Jiri Kosina
2019-02-12 14:01               ` Michal Hocko
2019-03-06 12:11   ` [PATCH 0/3] mincore() and IOCB_NOWAIT adjustments Jiri Kosina
2019-03-06 22:35     ` Andrew Morton
2019-03-06 22:48       ` Jiri Kosina
2019-03-06 23:23         ` Andrew Morton
2019-03-06 23:32           ` Dominique Martinet
2019-03-06 23:38             ` Andrew Morton
2019-03-09 16:53               ` Linus Torvalds
2019-03-12 14:17   ` [PATCH v2 0/2] prevent mincore() page cache leaks Vlastimil Babka
2019-03-12 14:17     ` [PATCH v2 1/2] mm/mincore: make mincore() more conservative Vlastimil Babka
2019-03-12 14:17     ` [PATCH v2 2/2] mm/mincore: provide mapped status when cached status is not allowed Vlastimil Babka

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190131113223.GU18811@dhcp22.suse.cz \
    --to=mhocko@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=asmadeus@codewreck.org \
    --cc=chrubis@suse.cz \
    --cc=daniel@gruss.cc \
    --cc=david@fromorbit.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jannh@google.com \
    --cc=jikos@kernel.org \
    --cc=kevin@guarana.org \
    --cc=kirill@shutemov.name \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=luto@amacapital.net \
    --cc=peterz@infradead.org \
    --cc=tj@kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=vbabka@suse.cz \
    --cc=willy@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).