From: Christoph Hellwig <hch@infradead.org>
To: linux-man@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Subject: [PATCH] update the sync.2 man page
Date: Tue, 9 Feb 2016 08:21:34 -0800 [thread overview]
Message-ID: <20160209162134.GA18634@infradead.org> (raw)
Clarify the description a bit, and document the Linux data integrity
guarantees.
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/man2/sync.2 b/man2/sync.2
index 5e222cb..28a42c4 100644
--- a/man2/sync.2
+++ b/man2/sync.2
@@ -35,7 +35,7 @@
.\"
.TH SYNC 2 2015-08-08 "Linux" "Linux Programmer's Manual"
.SH NAME
-sync, syncfs \- commit buffer cache to disk
+sync, syncfs \- commit filesystem caches to disk
.SH SYNOPSIS
.B #include <unistd.h>
.sp
@@ -64,8 +64,8 @@ _GNU_SOURCE
.ad
.SH DESCRIPTION
.BR sync ()
-causes all buffered modifications to file metadata and data to be
-written to the underlying filesystems.
+causes all pending modifications to file system metadata and cached file
+data to be written to the underlying filesystems.
.BR syncfs ()
is like
@@ -108,16 +108,21 @@ In glibc 2.2.1 and earlier,
it was "int sync(void)", and
.BR sync ()
always returned 0.
-.SH BUGS
+
According to the standard specification (e.g., POSIX.1-2001),
.BR sync ()
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.)
+writing is done. However Linux waits for I/O completions,
+and thus
+.BR sync ()
+or
+.BR syncfs ()
+provide the same guarantees as fsync called on every file in
+the system or filesystem respectively.
+.SH BUGS
+Before version 1.3.20 Linux did not wait for I/O to complete
+before returning.
.SH SEE ALSO
-.BR bdflush (2),
.BR fdatasync (2),
.BR fsync (2),
.BR sync (1)
next reply other threads:[~2016-02-09 16:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-09 16:21 Christoph Hellwig [this message]
2016-02-10 16:00 ` [PATCH] update the sync.2 man page Ross Zwisler
2016-02-11 12:35 ` Michael Kerrisk (man-pages)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160209162134.GA18634@infradead.org \
--to=hch@infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-man@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).