From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Chaloupka Subject: Re: [PATCH] statfs.2 does not describe f_flag field Date: Wed, 04 Feb 2015 14:01:19 +0100 Message-ID: <54D2181F.9070300@redhat.com> References: <20150204084843.29485.58701.stgit@unused-4-157.brq.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-man-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org Cc: schwab-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-man , Christoph Hellwig , Alexander Viro List-Id: linux-man@vger.kernel.org On 02/04/2015 12:51 PM, Michael Kerrisk (man-pages) wrote: > Hi Jan, > > On 4 February 2015 at 09:48, Jan Chaloupka wrote: >> Based on kernel commit [1], new flag f_flag is added to statfs struct. >> >> Before kernel 2.6.36, glibc's statvfs.f_flags was computed be iterating >> through all mounted points. This was inefficient and could cause a delay. >> Since kernel 2.6.36, statfs struct has new field f_flag, which already >> extracts mount options without iterating through mount point. >> statfs.f_flag flags of glibc and kernel are the same (plus kernel adds >> additional flag ST_VALID used only internally). So no matter what version >> of kernel is used, flags does not change. >> >> Flags used in statfs.f_flags can be enumerated from upstreams's >> glibc/internal_statvfs.c, lines 155-173. Nine flags in sum: >> >> ST_RDONLY = 1 >> ST_NOSUID = 2 >> ST_NODEV = 4 >> ST_NOEXEC = 8 >> ST_SYNCHRONOUS = 16 >> ST_MANDLOCK = 64 >> ST_NOATIME = 1024 >> ST_NODIRATIME = 2048 >> ST_RELATIME = 4096 >> >> This patch describes missing flag. >> >> [1] https://github.com/torvalds/linux/commit/365b18189789bfa1acd9939e6312b8a4b4577b28 > Thanks for the heads up. But this patch is a bit muddled, since it > mixes details about statfs(2) and statvfs(3). Yes. As kernel copied all the flags, it is now duplicated. But you are right it more suites for statvfs(2). > I've instead made some more detailed changes for the statfs(2) and statvfs(2) pages. > Thanks. > > Thanks, > > Michael > > >> Signed-off-by: Jan Chaloupka >> --- >> man2/statfs.2 | 28 +++++++++++++++++++++++++++- >> 1 file changed, 27 insertions(+), 1 deletion(-) >> >> diff --git a/man2/statfs.2 b/man2/statfs.2 >> index 714bc7c..46cfa5f 100644 >> --- a/man2/statfs.2 >> +++ b/man2/statfs.2 >> @@ -65,7 +65,9 @@ struct statfs { >> fsid_t f_fsid; /* filesystem id */ >> __SWORD_TYPE f_namelen; /* maximum length of filenames */ >> __SWORD_TYPE f_frsize; /* fragment size (since Linux 2.6) */ >> - __SWORD_TYPE f_spare[5]; >> + __SWORD_TYPE f_flags; /* mount flags of filesystem >> + (since Linux 2.6.36) */ >> + __SWORD_TYPE f_spare[4]; >> }; >> >> Filesystem types: >> @@ -146,6 +148,30 @@ Most of these MAGIC constants are defined in >> .IR /usr/include/linux/magic.h , >> and some are hardcoded in kernel sources. >> .PP >> +Mount flags of >> +.I f_flags >> +field are extracted from an option string of a mount point defined in >> +.BR mount (8). >> +The field can be combination of the following flags >> +(corresponding mount options are in the right column): >> +.in >> +.nf >> + >> + ST_RDONLY ro >> + ST_NOSUID nosuid >> + ST_NOEXEC noexec >> + ST_NODEV nodev >> + ST_SYNCHRONOUS sync >> + ST_MANDLOCK mand >> + ST_NOATIME noatime >> + ST_NODIRATIME nodiratime >> + ST_RELATIME relatime >> + >> +.fi >> +.in >> +For kernel less than 2.6.36 option flags are extracted by iterating >> +through individual mount points which can be inefficient and cause delay. >> +.PP >> Nobody knows what >> .I f_fsid >> is supposed to contain (but see below). >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html