From: Matthew Wilcox <willy@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: linux-cachefs@redhat.com, linux-afs@lists.infradead.org,
Andrew W Elble <aweits@rit.edu>, Jeff Layton <jlayton@kernel.org>,
ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/3] netfs: fix test for whether we can skip read when writing beyond EOF
Date: Mon, 21 Jun 2021 15:50:49 +0100 [thread overview]
Message-ID: <YNCnSQyKWqV8SkRs@casper.infradead.org> (raw)
In-Reply-To: <162391826758.1173366.11794946719301590013.stgit@warthog.procyon.org.uk>
On Thu, Jun 17, 2021 at 09:24:27AM +0100, David Howells wrote:
> From: Jeff Layton <jlayton@kernel.org>
>
> It's not sufficient to skip reading when the pos is beyond the EOF.
> There may be data at the head of the page that we need to fill in
> before the write.
>
> Add a new helper function that corrects and clarifies the logic of
> when we can skip reads, and have it only zero out the part of the page
> that won't have data copied in for the write.
>
> Finally, don't set the page Uptodate after zeroing. It's not up to date
> since the write data won't have been copied in yet.
>
> [DH made the following changes:
>
> - Prefixed the new function with "netfs_".
>
> - Don't call zero_user_segments() for a full-page write.
>
> - Altered the beyond-last-page check to avoid a DIV instruction and got
> rid of then-redundant zero-length file check.
> ]
>
> Fixes: e1b1240c1ff5f ("netfs: Add write_begin helper")
> Reported-by: Andrew W Elble <aweits@rit.edu>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: ceph-devel@vger.kernel.org
> Link: https://lore.kernel.org/r/20210613233345.113565-1-jlayton@kernel.org/
> Link: https://lore.kernel.org/r/162367683365.460125.4467036947364047314.stgit@warthog.procyon.org.uk/ # v1
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
next prev parent reply other threads:[~2021-06-21 14:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 8:23 [PATCH v2 0/3] netfs, afs: Fix netfs_write_begin and THP handling David Howells
2021-06-17 8:24 ` [PATCH v2 3/3] netfs: fix test for whether we can skip read when writing beyond EOF David Howells
2021-06-21 14:50 ` Matthew Wilcox [this message]
2021-06-18 3:46 ` [PATCH v2 0/3] netfs, afs: Fix netfs_write_begin and THP handling Al Viro
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