From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Mikulas Patocka <mpatocka@redhat.com>,
Jens Axboe <axboe@kernel.dk>,
Jeff Chua <jeff.chua.linux@gmail.com>,
Lai Jiangshan <laijs@cn.fujitsu.com>, Jan Kara <jack@suse.cz>,
lkml <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH] Introduce a method to catch mmap_region (was: Recent kernel "mount" slow)
Date: Wed, 28 Nov 2012 22:37:27 -0800 [thread overview]
Message-ID: <CA+55aFwL9-yOfCHskXyiCJ3YKB0MgaOJ5-XrvWBtH+URCowfcg@mail.gmail.com> (raw)
In-Reply-To: <20121129063043.GJ4939@ZenIV.linux.org.uk>
On Wed, Nov 28, 2012 at 10:30 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Note that sync_blockdev() a few lines prior to that is good only if we
> have no other processes doing write(2) (or dirtying the mmapped pages,
> for that matter). The window isn't too wide, but...
So with Mikulas' patches, the write actually would block (at write
level) due to the locking. The mmap'ed patches may be around and
flushed, but the logic to not allow currently *active* mmaps (with the
rather nasty random -EBUSY return value) should mean that there is no
race.
Or rather, there's a race, but it results in that EBUSY thing.
With my simplfied locking, the sync_blockdev() is right before (not a
few lines prior) to the kill_bdev(), and in a perfect world they'd
actually be one single operation ("write back and invalidate pages
with the wrong block-size"). But they aren't.
Linus
next prev parent reply other threads:[~2012-11-29 6:37 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAAJw_ZtbhE5Jtd4PsWx8a23QdFTW7aMrKBmRf-bo5Wrean9Xhg@mail.gmail.com>
2012-11-20 18:09 ` Recent kernel "mount" slow Jan Kara
2012-11-21 15:46 ` Jeff Chua
2012-11-22 14:30 ` Jeff Chua
2012-11-22 19:21 ` Linus Torvalds
2012-11-23 13:24 ` Jens Axboe
2012-11-23 22:21 ` Jeff Chua
2012-11-23 23:31 ` Jeff Chua
2012-11-23 23:48 ` Jeff Chua
2012-11-24 21:09 ` Mikulas Patocka
2012-11-24 23:23 ` Jeff Chua
2012-11-27 5:57 ` Jeff Chua
2012-11-27 7:38 ` Jens Axboe
2012-11-27 7:44 ` Jens Axboe
2012-11-27 8:45 ` Jeff Chua
2012-11-27 10:06 ` Jeff Chua
2012-11-27 12:33 ` Jens Axboe
2012-11-28 3:57 ` Mikulas Patocka
2012-11-28 8:33 ` Jens Axboe
2012-11-28 13:05 ` Jeff Chua
2012-11-28 17:25 ` [PATCH] Introduce a method to catch mmap_region (was: Recent kernel "mount" slow) Mikulas Patocka
2012-11-28 19:15 ` Linus Torvalds
2012-11-28 19:43 ` Al Viro
2012-11-28 19:53 ` Linus Torvalds
2012-11-28 22:01 ` [PATCH v2] Do a proper locking for mmap and block size change Mikulas Patocka
2012-11-29 17:19 ` Linus Torvalds
2012-11-29 18:23 ` Mikulas Patocka
2012-11-29 18:46 ` Linus Torvalds
2012-11-29 19:02 ` Linus Torvalds
2012-11-29 19:15 ` Chris Mason
2012-11-29 19:26 ` Linus Torvalds
2012-11-29 19:48 ` Chris Mason
2012-11-29 19:55 ` Linus Torvalds
2012-11-29 20:10 ` Linus Torvalds
2012-11-29 20:52 ` Linus Torvalds
2012-11-29 21:29 ` Chris Mason
2012-11-29 22:16 ` Linus Torvalds
2012-11-29 22:36 ` Linus Torvalds
2012-11-30 1:16 ` Chris Mason
2012-11-30 2:13 ` Linus Torvalds
2012-11-30 2:27 ` Chris Mason
2012-11-30 2:49 ` Dave Chinner
2012-11-30 14:31 ` Chris Mason
2012-11-30 16:42 ` Linus Torvalds
2012-11-30 16:36 ` Christoph Hellwig
2012-11-30 22:40 ` Dave Chinner
2012-11-30 23:09 ` Christoph Hellwig
2012-11-29 19:50 ` Linus Torvalds
2012-11-28 19:50 ` [PATCH] Introduce a method to catch mmap_region (was: Recent kernel "mount" slow) Mikulas Patocka
2012-11-28 20:03 ` Linus Torvalds
2012-11-28 20:13 ` Linus Torvalds
2012-11-28 20:32 ` Linus Torvalds
2012-11-28 20:47 ` Linus Torvalds
2012-11-28 22:10 ` Mikulas Patocka
2012-11-28 21:29 ` Mikulas Patocka
2012-11-28 22:52 ` Linus Torvalds
2012-11-28 23:13 ` Linus Torvalds
2012-11-29 1:20 ` Mikulas Patocka
2012-11-29 0:38 ` Mikulas Patocka
2012-11-29 2:04 ` Linus Torvalds
2012-11-29 2:58 ` Linus Torvalds
2012-11-29 6:16 ` Linus Torvalds
2012-11-29 6:25 ` Al Viro
2012-11-29 6:30 ` Al Viro
2012-11-29 6:37 ` Linus Torvalds [this message]
2012-11-29 6:45 ` Al Viro
2012-11-29 10:57 ` Jeff Chua
2012-11-29 6:33 ` Linus Torvalds
2012-11-29 14:12 ` Chris Mason
2012-11-29 17:26 ` Chris Mason
2012-11-29 17:26 ` Linus Torvalds
2012-11-29 17:51 ` Chris Mason
2012-11-29 18:12 ` Linus Torvalds
2012-11-28 3:59 ` [PATCH 1/2] percpu-rwsem: use synchronize_sched_expedited Mikulas Patocka
2012-11-28 4:01 ` [PATCH 2/2] block_dev: don't take the write lock if block size doesn't change Mikulas Patocka
2012-11-28 14:24 ` Jeff Chua
2012-11-28 22:03 ` Mikulas Patocka
2012-11-28 14:19 ` [PATCH 1/2] percpu-rwsem: use synchronize_sched_expedited Jeff Chua
2012-11-30 0:06 ` Andrew Morton
2012-11-30 3:00 ` Mikulas Patocka
2012-11-30 13:42 ` Paul E. McKenney
2012-11-30 18:57 ` Oleg Nesterov
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=CA+55aFwL9-yOfCHskXyiCJ3YKB0MgaOJ5-XrvWBtH+URCowfcg@mail.gmail.com \
--to=torvalds@linux-foundation.org \
--cc=axboe@kernel.dk \
--cc=jack@suse.cz \
--cc=jeff.chua.linux@gmail.com \
--cc=laijs@cn.fujitsu.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mpatocka@redhat.com \
--cc=viro@zeniv.linux.org.uk \
/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).