linux-kernel - Re: [PATCH -next,v2] NFS: report and clear ENOSPC/EFBIG/EDQUOT writeback error on close() file

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Date:   Wed, 15 Jun 2022 09:34:31 +0800
From:   "chenxiaosong (A)" <chenxiaosong2@...wei.com>
To:     Trond Myklebust <trondmy@...merspace.com>,
        "anna@...nel.org" <anna@...nel.org>
CC:     "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "liuyongqiang13@...wei.com" <liuyongqiang13@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "yi.zhang@...wei.com" <yi.zhang@...wei.com>,
        "zhangxiaoxu5@...wei.com" <zhangxiaoxu5@...wei.com>
Subject: Re: [PATCH -next,v2] NFS: report and clear ENOSPC/EFBIG/EDQUOT
 writeback error on close() file

在 2022/6/15 3:48, Trond Myklebust 写道:
> NACK. How many times do I have to repeat that we do NOT clear the error
> log in flush()?
> 

close(2) manpage described:

> ENOSPC, EDQUOT: On NFS, these errors are not normally reported
> against the first write which exceeds the available storage space,
> but instead against a subsequent write(2), fsync(2), or close(2).

> A  careful programmer will check the return value of close(), since
> it is quite possible that errors on a previous write(2) operation are
> reported only on the final close() that releases the open file
> description.  Failing to check the return value when closing a file
> may lead to silent loss of data.  This can especially be observed 
> with NFS and with disk quota.

write(2) manpage described:

> Since Linux 4.13, errors from write-back come with a promise that they
> may be reported by subsequent.  write(2) requests, and will be
> reported by a subsequent fsync(2) (whether or not they were also
> reported by write(2)).

Both close(2) and write(2) manpage described: report writeback error 
(not clear error), especially the write(2) manpage described: will be 
reported by a subsequent fsync(2) whether or not they were also reported 
by write(2).

If ENOSPC/EFBIG/EDQUOT writeback error can be cleared on write(), maybe 
it is better to be cleared on close() instead of saving the error for 
next open().