From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: Murphy Zhou <jencce.kernel@gmail.com>
Cc: linux-ext4@vger.kernel.org, fstests@vger.kernel.org
Subject: Re: ext4 dio RWF_NOWAIT change
Date: Fri, 7 Feb 2020 10:38:24 -0500 [thread overview]
Message-ID: <20200207153824.GA122530@mit.edu> (raw)
In-Reply-To: <20200205091344.u5c3nnblezzh5xgb@xzhoux.usersys.redhat.com>
On Wed, Feb 05, 2020 at 05:13:44PM +0800, Murphy Zhou wrote:
> Hi,
>
> Kernel commit 378f32bab3714f04c4e0c3aee4129f6703805550
> Author: Matthew Bobrowski <mbobrowski@mbobrowski.org>
> Date: Tue Nov 5 23:02:39 2019 +1100
>
> ext4: introduce direct I/O write using iomap infrastructure
>
>
> Changed the logic of dio+RWF_NOWAIT
>
> from:
>
> - if (!inode_trylock(inode)) {
> - if (iocb->ki_flags & IOCB_NOWAIT)
> - return -EAGAIN;
> - inode_lock(inode);
> - }
>
>
> to:
>
> + if (iocb->ki_flags & IOCB_NOWAIT) {
> + if (!inode_trylock(inode))
> + return -EAGAIN;
> + } else {
> + inode_lock(inode);
> + }
>
>
> fstests generic/471 expecet EAGAIN on this situation, so it started to
> fail since than.
I don't understand why this specific change would cause the situation.
In the generic/471 test, here iocb->ki_flags will have IOCB_NOWAIT
set, and in that case I don't see how there would be a change in
behavior with respect to EAGAIN being returned.
In any case, I've been suppressing generic/471 because of concerns
that the test is bogus so I hadn't noticed. From
kvm-xfstests/test-appliance/files/root/fs/global_exclude:
# The test generic/471 tests the RWF_NOWAIT flag; however
# how it is supposed to work with file systems is disputed,
# and not all device drivers support it. As a result
# it doesn't work if an LVM device driver is in use (as is the
# case with gce-xfstests). So let's suppress it for now. For
# more details see:
# https://lore.kernel.org/linux-block/20190723220502.GX7777@dread.disaster.area/
generic/471
- Ted
next prev parent reply other threads:[~2020-02-07 15:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-05 9:13 ext4 dio RWF_NOWAIT change Murphy Zhou
2020-02-07 15:38 ` Theodore Y. Ts'o [this message]
2020-02-12 10:50 ` Murphy Zhou
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