From: Dominique Martinet <asmadeus@codewreck.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: v9fs-developer@lists.sourceforge.net,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Netdev <netdev@vger.kernel.org>
Subject: Re: [GIT PULL] 9p updates for 5.1
Date: Mon, 18 Mar 2019 01:04:02 +0100 [thread overview]
Message-ID: <20190318000402.GA24768@nautica> (raw)
In-Reply-To: <CAHk-=wgywWzGP-UszbL4csXpk4_h0w5PbkZYdaTpBzue82btfQ@mail.gmail.com>
Linus Torvalds wrote on Sun, Mar 17, 2019:
> Hmm. I wonder what makes it valid to have concurrent updates to
> i_size? Yes, yes, you added that spinlock to make the update itself
> atomic on 32-bit, but it sounds a bit odd in the first place to have
> two things possibly changing the size of a file at the same time...
If the inode attributes are currently invalid (for example after
v9fs_invalidate_inode_attr()) then two concurrent user getattr requests
for the same inode will send two network requests which can both update
the i_size.
With cache=fscache or loose a write could also be concurrent with such
an update.
I plan on improving the first case with some "being revalidated" logic
now this pattern got reported but I don't think the second one can be
avoided, so that fix is still necessary in the long run afaict.
Thanks,
--
Dominique
next prev parent reply other threads:[~2019-03-18 0:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-17 14:25 [GIT PULL] 9p updates for 5.1 Dominique Martinet
2019-03-17 16:15 ` Linus Torvalds
2019-03-18 0:04 ` Dominique Martinet [this message]
2019-03-17 16:45 ` pr-tracker-bot
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