From: Eric Blake <eblake@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, mreitz@redhat.com
Subject: Re: [PATCH for-5.1 2/2] file-posix: Allow byte-aligned O_DIRECT with NFS
Date: Fri, 10 Jul 2020 09:39:22 -0500 [thread overview]
Message-ID: <83827826-87c8-8227-2fbc-22b7ff2fb6e6@redhat.com> (raw)
In-Reply-To: <20200710142149.40962-3-kwolf@redhat.com>
On 7/10/20 9:21 AM, Kevin Wolf wrote:
> Since commit a6b257a08e3 ('file-posix: Handle undetectable alignment'),
> we assume that if we open a file with O_DIRECT and alignment probing
> returns 1, we just couldn't find out the real alignment requirement
> because some filesystems make the requirement only for allocated blocks.
> In this case, a safe default of 4k is used.
>
> This is too strict NFS, which does actually allow byte-aligned requests
strict for
> even with O_DIRECT. Because we can't distinguish both cases with generic
> code, let's just look at the file system magic and disable
> s->needs_alignment for NFS. This way, O_DIRECT can still be used on NFS
> for images that are not aligned to 4k.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
> block/file-posix.c | 26 +++++++++++++++++++++++++-
> 1 file changed, 25 insertions(+), 1 deletion(-)
>
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2020-07-10 14:40 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 14:21 [PATCH for-5.1 0/2] qemu-img convert: Fix abort with unaligned image size Kevin Wolf
2020-07-10 14:21 ` [PATCH for-5.1 1/2] block: Require aligned image size to avoid assertion failure Kevin Wolf
2020-07-10 14:37 ` Eric Blake
2020-07-13 11:19 ` Max Reitz
2020-07-13 11:52 ` Max Reitz
2020-07-13 14:29 ` Kevin Wolf
2020-07-14 9:56 ` Max Reitz
2020-07-14 11:08 ` Kevin Wolf
2020-07-14 16:22 ` Max Reitz
2020-07-15 9:20 ` Kevin Wolf
2020-07-13 16:33 ` Nir Soffer
2020-07-13 16:56 ` Kevin Wolf
2020-07-15 13:22 ` Nir Soffer
2020-07-15 13:42 ` Kevin Wolf
2020-07-15 14:03 ` Nir Soffer
2020-07-15 14:03 ` Daniel P. Berrangé
2020-07-10 14:21 ` [PATCH for-5.1 2/2] file-posix: Allow byte-aligned O_DIRECT with NFS Kevin Wolf
2020-07-10 14:39 ` Eric Blake [this message]
2020-07-13 16:29 ` Nir Soffer
2020-07-10 14:43 ` [PATCH for-5.1 0/2] qemu-img convert: Fix abort with unaligned image size no-reply
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