Hi Jan, On 4 February 2015 at 09:48, Jan Chaloupka <jchaloup@xxxxxxxxxx> 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). I've instead made some more detailed changes for the statfs(2) and statvfs(2) pages. Thanks, Michael > Signed-off-by: Jan Chaloupka <jchaloup@xxxxxxxxxx> > --- > 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). > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
