From: Jeff Layton <jlayton@kernel.org>
To: viro@zeniv.linux.org.uk
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, andres@anarazel.de,
willy@infradead.org, dhowells@redhat.com, hch@infradead.org,
jack@suse.cz, akpm@linux-foundation.org
Subject: Re: [PATCH v3 0/3] vfs: have syncfs() return error when there are writeback errors
Date: Wed, 12 Feb 2020 07:21:19 -0500 [thread overview]
Message-ID: <13f20458cd8b72026cec364b6b8b8e4d636ebe94.camel@kernel.org> (raw)
In-Reply-To: <20200207170423.377931-1-jlayton@kernel.org>
On Fri, 2020-02-07 at 12:04 -0500, Jeff Layton wrote:
> You're probably wondering -- Where are v1 and v2 sets?
>
> I did the first couple of versions of this set back in 2018, and then
> got dragged off to work on other things. I'd like to resurrect this set
> though, as I think it's valuable overall, and I have need of it for some
> other work I'm doing.
>
> Currently, syncfs does not return errors when one of the inodes fails to
> be written back. It will return errors based on the legacy AS_EIO and
> AS_ENOSPC flags when syncing out the block device fails, but that's not
> particularly helpful for filesystems that aren't backed by a blockdev.
> It's also possible for a stray sync to lose those errors.
>
> The basic idea is to track writeback errors at the superblock level,
> so that we can quickly and easily check whether something bad happened
> without having to fsync each file individually. syncfs is then changed
> to reliably report writeback errors, and a new ioctl is added to allow
> userland to get at the current errseq_t value w/o having to sync out
> anything.
>
> I do have a xfstest for this. I do not yet have manpage patches, but
> I'm happy to roll some once there is consensus on the interface.
>
> Caveats:
>
> - Having different behavior for an O_PATH descriptor in syncfs is
> a bit odd, but it means that we don't have to grow struct file. Is
> that acceptable from an API standpoint?
>
There are a couple of other options besides requiring an O_PATH fd here:
1) we could just add a new errseq_t field to struct file for this. On my
machine (x86_64) there is 4 bytes of padding at the end of struct file.
An errseq_t would slot in there without changing the slab object size.
YMMV on other arches of course.
2) we could add a new fcntl command value (F_SYNCFS or something?), that
would flip the fd to being suitable for syncfs. If you tried to use the
fd to do a fsync at that point, we could return an error.
Anyone else have other thoughts on how best to do this?
> - This adds a new generic fs ioctl to allow userland to scrape the
> current superblock's errseq_t value. It may be best to present this
> to userland via fsinfo() instead (once that's merged). I'm fine with
> dropping the last patch for now and reworking it for fsinfo if so.
>
To be clear, as I stated in earlier replies, I think we can drop the
ioctl. If we did want something like this, I think we'd want to expose
it via fsinfo() instead, and that could be done after the syncfs changes
went in.
> Jeff Layton (3):
> vfs: track per-sb writeback errors and report them to syncfs
> buffer: record blockdev write errors in super_block that it backs
> vfs: add a new ioctl for fetching the superblock's errseq_t
>
> fs/buffer.c | 2 ++
> fs/ioctl.c | 4 ++++
> fs/open.c | 6 +++---
> fs/sync.c | 9 ++++++++-
> include/linux/errseq.h | 1 +
> include/linux/fs.h | 3 +++
> include/linux/pagemap.h | 5 ++++-
> include/uapi/linux/fs.h | 1 +
> lib/errseq.c | 33 +++++++++++++++++++++++++++++++--
> 9 files changed, 57 insertions(+), 7 deletions(-)
>
--
Jeff Layton <jlayton@kernel.org>
prev parent reply other threads:[~2020-02-12 12:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-07 17:04 [PATCH v3 0/3] vfs: have syncfs() return error when there are writeback errors Jeff Layton
2020-02-07 17:04 ` [PATCH v3 1/3] vfs: track per-sb writeback errors and report them to syncfs Jeff Layton
2020-02-07 17:04 ` [PATCH v3 2/3] buffer: record blockdev write errors in super_block that it backs Jeff Layton
2020-02-07 17:04 ` [PATCH v3 3/3] vfs: add a new ioctl for fetching the superblock's errseq_t Jeff Layton
2020-02-07 20:52 ` [PATCH v3 0/3] vfs: have syncfs() return error when there are writeback errors Dave Chinner
2020-02-07 21:20 ` Andres Freund
2020-02-07 22:05 ` Jeff Layton
2020-02-07 22:21 ` Andres Freund
2020-02-10 21:46 ` Dave Chinner
2020-02-10 23:59 ` Andres Freund, David Howells
2020-02-11 0:04 ` Andres Freund
2020-02-11 0:48 ` Dave Chinner
2020-02-11 1:31 ` Andres Freund
2020-02-11 12:57 ` Jeff Layton
2020-02-12 12:21 ` Jeff Layton [this message]
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