GNU bug report logs - #19995
doc: Adds a bug section to sync.1 page to draw attention to unexpected behavior allowed by POSIX.

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: saulery <at> free.fr
To: bug-coreutils <at> gnu.org
Cc: Stéphane Aulery <saulery <at> free.fr>
Subject: doc: Adds a bug section to sync.1 page to draw attention to
 unexpected behavior allowed by POSIX.
Date: Wed,  4 Mar 2015 01:06:01 +0100

From: Stéphane Aulery <saulery <at> free.fr>

Almost identical copy of sync.2.

Debian bug #507085 reported by jidanni <at> jidanni.org

Signed-off-by: Stéphane Aulery <saulery <at> free.fr>
---
 man/sync.x | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/man/sync.x b/man/sync.x
index 79fee22..5b85bba 100644
--- a/man/sync.x
+++ b/man/sync.x
@@ -2,5 +2,10 @@
 sync \- Synchronize cached writes to persistent storage
 [DESCRIPTION]
 .\" Add any additional description here
+[BUGS]
+According to the standard specification (e.g., POSIX.1-2001), sync()
+syscall schedules the writes, but may return before the actual writing is
+done. However, since version 1.3.20 Linux does actually wait. (This still
+does not guarantee data integrity: modern disks have large caches.)
 [SEE ALSO]
 fdatasync(2), fsync(2), sync(2), syncfs(2)
-- 
2.1.4

Message #10 received at 19995 <at> debbugs.gnu.org (full text, mbox):

From: Stéphane Aulery <saulery <at> free.fr>
To: 19995 <at> debbugs.gnu.org
Subject: [patch] sync.1: prevent data loss (reposte of my previous merged
 message)
Date: Thu, 5 Mar 2015 12:45:46 +0100

Hello,

A Debian user reported [1] that sync.1 man page is incomplete unlike sync.2
There is no mention of the unexpected behavior allowed by POSIX, which can
cause data loss.

This patch provides a possible correction.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=507085

Regards,

-- 
Stéphane Aulery

Message #17 received at 19995-done <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Stéphane Aulery <saulery <at> free.fr>,
 19995-done <at> debbugs.gnu.org
Subject: Re: bug#19995: [patch] sync.1: prevent data loss (reposte of my
 previous merged message)
Date: Thu, 05 Mar 2015 12:23:44 +0000

On 05/03/15 11:45, Stéphane Aulery wrote:
> Hello,
> 
> A Debian user reported [1] that sync.1 man page is incomplete unlike sync.2
> There is no mention of the unexpected behavior allowed by POSIX, which can
> cause data loss.
> 
> This patch provides a possible correction.
> 
> [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=507085

How about I apply this in your name instead?

diff --git a/man/sync.x b/man/sync.x
index 79fee22..18ee3fc 100644
--- a/man/sync.x
+++ b/man/sync.x
@@ -2,5 +2,8 @@
 sync \- Synchronize cached writes to persistent storage
 [DESCRIPTION]
 .\" Add any additional description here
+[BUGS]
+Persistence guarantees vary per system.
+See the system calls below for more details.
 [SEE ALSO]
 fdatasync(2), fsync(2), sync(2), syncfs(2)

Message #25 received at 19995-done <at> debbugs.gnu.org (full text, mbox):

From: Stéphane Aulery <saulery <at> free.fr>
To: Pádraig Brady <P <at> draigBrady.com>
Cc: 19995-done <at> debbugs.gnu.org
Subject: Re: bug#19995: [patch] sync.1: prevent data loss (reposte of my
 previous merged message)
Date: Thu, 5 Mar 2015 14:20:14 +0100

Hello Brady,

Le jeudi 05 mars 2015 à 12:23:44, Pádraig Brady a écrit :
> 
> How about I apply this in your name instead?
> 
> diff --git a/man/sync.x b/man/sync.x
> index 79fee22..18ee3fc 100644
> --- a/man/sync.x
> +++ b/man/sync.x
> @@ -2,5 +2,8 @@
>  sync \- Synchronize cached writes to persistent storage
>  [DESCRIPTION]
>  .\" Add any additional description here
> +[BUGS]
> +Persistence guarantees vary per system.
> +See the system calls below for more details.
>  [SEE ALSO]
>  fdatasync(2), fsync(2), sync(2), syncfs(2)

It's good for me. Thank you.

Regards,

-- 
Stéphane Aulery

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