linux-kernel - Re: [PATCH v2] sync.2: syncfs() now returns errors if writeback fails

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Date:   Fri, 26 Jun 2020 11:06:19 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     mtk.manpages@...il.com, linux-man@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        ebiggers@...nel.org
Subject: Re: [PATCH v2] sync.2: syncfs() now returns errors if writeback fails

Hi Jeff,

On 6/26/20 1:37 AM, Jeff Layton wrote:
> A patch has been merged for v5.8 that changes how syncfs() reports
> errors. Change the sync() manpage accordingly.
> 
> Signed-off-by: Jeff Layton <jlayton@...nel.org>

Thanks. Patch applied. (I've not yet pushed it, in case any 
review comments might still come in.)

Cheers,

Michael

> ---
>  man2/sync.2 | 24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
>  v2: update the NOTES verbiage according to Eric's suggestion
> 
> diff --git a/man2/sync.2 b/man2/sync.2
> index 7198f3311b05..61e994c5affc 100644
> --- a/man2/sync.2
> +++ b/man2/sync.2
> @@ -86,11 +86,26 @@ to indicate the error.
>  is always successful.
>  .PP
>  .BR syncfs ()
> -can fail for at least the following reason:
> +can fail for at least the following reasons:
>  .TP
>  .B EBADF
>  .I fd
>  is not a valid file descriptor.
> +.TP
> +.B EIO
> +An error occurred during synchronization.
> +This error may relate to data written to any file on the filesystem, or on
> +metadata related to the filesytem itself.
> +.TP
> +.B ENOSPC
> +Disk space was exhausted while synchronizing.
> +.TP
> +.BR ENOSPC ", " EDQUOT
> +Data was written to a files on NFS or another filesystem which does not
> +allocate space at the time of a
> +.BR write (2)
> +system call, and some previous write failed due to insufficient
> +storage space.
>  .SH VERSIONS
>  .BR syncfs ()
>  first appeared in Linux 2.6.39;
> @@ -121,6 +136,13 @@ or
>  .BR syncfs ()
>  provide the same guarantees as fsync called on every file in
>  the system or filesystem respectively.
> +.PP
> +In mainline kernel versions prior to 5.8,
> +.\" commit 735e4ae5ba28c886d249ad04d3c8cc097dad6336
> +.BR syncfs ()
> +will only fail when passed a bad file descriptor (EBADF). In 5.8
> +and later kernels, it will also report an error if one or more inodes failed
> +to be written back since the last syncfs call.
>  .SH BUGS
>  Before version 1.3.20 Linux did not wait for I/O to complete
>  before returning.
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/