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From: Jens Axboe <axboe@kernel.dk>
To: linux-fsdevel@vger.kernel.org
Cc: torvalds@linux-foundation.org, viro@zeniv.linux.org.uk
Subject: [PATCHSET 0/2] fs: Support for LOOKUP_NONBLOCK / RESOLVE_NONBLOCK
Date: Thu, 10 Dec 2020 13:01:12 -0700	[thread overview]
Message-ID: <20201210200114.525026-1-axboe@kernel.dk> (raw)

Hi,

This adds support for just doing the RCU based (and non-blocking) part
of path resolution. The main motivation is for io_uring to be able to
do saner/faster open, so we don't always have to go async, particularly
for the fast path of the data already being cached.

Internally that is presented as LOOKUP_NONBLOCK, which depends on
LOOKUP_RCU for doing the right thing. If we terminate the RCU part of the
lookup, then we return -EAGAIN if LOOKUP_NONBLOCK is also set.

The second patch is enabling this through openat2() as well, by adding
a RESOLVE_NONBLOCK that can be passed in struct open_how ->resolve as
well. Basic test case:

[root@archlinux liburing]# echo 3 > /proc/sys/vm/drop_caches 
[root@archlinux liburing]# test/do-open2 /etc/nanorc
open: -1
openat2: Resource temporarily unavailable
[root@archlinux liburing]# touch /etc/nanorc
[root@archlinux liburing]# test/do-open2 /etc/nanorc
open: 3

-- 
Jens Axboe



             reply	other threads:[~2020-12-10 20:02 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-10 20:01 Jens Axboe [this message]
2020-12-10 20:01 ` [PATCH 1/2] fs: add support for LOOKUP_NONBLOCK Jens Axboe
2020-12-10 20:53   ` Linus Torvalds
2020-12-10 21:06     ` Jens Axboe
2020-12-11  2:45       ` Al Viro
2020-12-11 16:05         ` Jens Axboe
2020-12-11 17:20           ` Al Viro
2020-12-11 17:35             ` Linus Torvalds
2020-12-11 18:50             ` Jens Axboe
2020-12-11 21:51               ` Al Viro
2020-12-11 23:47                 ` Jens Axboe
2020-12-11 17:33           ` Matthew Wilcox
2020-12-11 18:55             ` Jens Axboe
2020-12-11  2:35   ` Al Viro
2020-12-11 15:57     ` Jens Axboe
2020-12-11 17:21       ` Linus Torvalds
2020-12-11 17:29         ` Al Viro
2020-12-11 17:38           ` Al Viro
2020-12-11 17:44           ` Linus Torvalds
2020-12-11 21:46           ` Jens Axboe
2020-12-10 20:01 ` [PATCH 2/2] fs: expose LOOKUP_NONBLOCK through openat2() RESOLVE_NONBLOCK Jens Axboe
2020-12-10 22:29   ` Dave Chinner
2020-12-10 23:12     ` Jens Axboe
2020-12-10 23:29     ` Linus Torvalds
2020-12-11  0:58       ` Dave Chinner
2020-12-11  1:01         ` Linus Torvalds
2020-12-11  3:45           ` Dave Chinner
2020-12-11 18:07             ` Linus Torvalds

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