From: Kent Overstreet <kent.overstreet@gmail.com>
To: David Howells <dhowells@redhat.com>
Cc: willy@infradead.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] mm: Stop filemap_read() from grabbing a superfluous page
Date: Wed, 13 Oct 2021 11:58:04 -0400 [thread overview]
Message-ID: <YWcCDE6rz1xgh9vD@moria.home.lan> (raw)
In-Reply-To: <163360810881.1636291.17477809397516812670.stgit@warthog.procyon.org.uk>
On Thu, Oct 07, 2021 at 01:01:48PM +0100, David Howells wrote:
> Under some circumstances, filemap_read() will allocate sufficient pages to
> read to the end of the file, call readahead/readpages on them and copy the
> data over - and then it will allocate another page at the EOF and call
> readpage on that and then ignore it. This is unnecessary and a waste of
> time and resources.
>
> filemap_read() *does* check for this, but only after it has already done
> the allocation and I/O. Fix this by checking before calling
> filemap_get_pages() also.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Kent Overstreet <kent.overstreet@gmail.com>
> cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> cc: linux-mm@kvack.org
> cc: linux-fsdevel@vger.kernel.org
> Link: https://lore.kernel.org/r/160588481358.3465195.16552616179674485179.stgit@warthog.procyon.org.uk/
Acked-by: Kent Overstreet <kent.overstreet@gmail.com>
prev parent reply other threads:[~2021-10-13 15:58 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-07 12:01 David Howells
2021-10-13 15:58 ` Kent Overstreet [this message]
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