Eric Wong <normalperson@yhbt.net> wrote:
> Ondřej Bílka <neleai@seznam.cz> wrote:
> > > Sorry for the delay. I've only tested on 3.12+ so far on x86_64.
> > > I'll try to get a VM setup on <2.6.36 soon
> >
> > Did you test also with these kernels?
>
> Unfortunately the machine running 2.6.32.x CentOS 6.x kernel
> already had Linux commit 365b18189789bfa1acd9939e6312b8a4b4577b28
> (add f_flags to struct statfs(64)) backported to it :<
>
> Probably just be easier for me to test with the following kernel patch
> than to get an older kernel running:
>
> --- a/fs/statfs.c
> +++ b/fs/statfs.c
> @@ -42,7 +42,7 @@ static int flags_by_sb(int s_flags)
>
> static int calculate_f_flags(struct vfsmount *mnt)
> {
> - return ST_VALID | flags_by_mnt(mnt->mnt_flags) |
> + return flags_by_mnt(mnt->mnt_flags) |
> flags_by_sb(mnt->mnt_sb->s_flags);
> }
>
I tested with the above patch applied 3.14 kernel and verified it
correctly falls back to using stat/fstat if the ST_VALID flag is
missing.
On an unpatched 3.14 kernel, the same executables/binaries avoid
stat/fstat when statvfs/fstatvfs are called.
I straced the following program to verify the presence/lack-of
extraneous stat/fstat syscalls after statfs/fstatfs:
strace /path/to/lib/ld-linux-x86-64.so.2 /tmp/statvfs
-------------------------- /tmp/statvfs.c ----------------------------
#include <sys/statvfs.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int main(int argc, char *argv[])
{
struct statvfs buf;
const char *path = argc == 2 ? argv[1] : "/";
int fd;
statvfs(path, &buf);
fd = open(path, O_DIRECTORY, O_RDONLY);
fstatvfs(fd, &buf);
return 0;
}
Original patch with updated commit message:
-------------------------------- 8< ---------------------------------
From: Eric Wong <normalperson@yhbt.net>
Subject: [PATCH] avoid stat/fstat in statvfs/fstatvfs
Delay the use of stat/fstat until stat data is required.
When the kernel returns ST_VALID, stat data is not used
by __internal_statvfs.
2014-05-27 Eric Wong <normalperson@yhbt.net>
[BZ #15132]
* sysdeps/unix/sysv/linux/internal_statvfs.c (__statvfs_getflags):
Call fstat64 or stat64 internally, depending on arguments passed.
Replace stat buffer argument with file descriptor argument.
(INTERNAL_STATVFS): Update arguments to match __statvfs_getflags.
* sysdeps/unix/sysv/linux/fstatvfs.c (fstatvfs):
Pass fd to __internal_statvfs instead of calling fstat64.
* sysdeps/unix/sysv/linux/fstatvfs64.c (__fstatvfs64):
Pass fd to __internal_statvfs64 instead of calling fstat64.
* sysdeps/unix/sysv/linux/statvfs.c (statvfs):
Pass -1 to __internal_statvfs instead of calling stat64.
* sysdeps/unix/sysv/linux/statvfs64.c (__statvfs64):
Pass -1 to __internal_statvfs64 instead of calling stat64.
---
sysdeps/unix/sysv/linux/fstatvfs.c | 4 ++--
sysdeps/unix/sysv/linux/fstatvfs64.c | 10 +++-------
sysdeps/unix/sysv/linux/internal_statvfs.c | 15 ++++++++-------
sysdeps/unix/sysv/linux/statvfs.c | 6 ++----
sysdeps/unix/sysv/linux/statvfs64.c | 10 +++-------
5 files changed, 18 insertions(+), 27 deletions(-)
@@ -22,7 +22,7 @@
#include <sys/statvfs.h>
extern void __internal_statvfs (const char *name, struct statvfs *buf,
- struct statfs *fsbuf, struct stat64 *st);
+ struct statfs *fsbuf, int fd);
int
@@ -36,7 +36,7 @@ fstatvfs (int fd, struct statvfs *buf)
return -1;
/* Convert the result. */
- __internal_statvfs (NULL, buf, &fsbuf, fstat64 (fd, &st) == -1 ? NULL : &st);
+ __internal_statvfs (NULL, buf, &fsbuf, fd);
/* We signal success if the statfs call succeeded. */
return 0;
@@ -25,7 +25,7 @@
extern void __internal_statvfs64 (const char *name, struct statvfs64 *buf,
- struct statfs64 *fsbuf, struct stat64 *st);
+ struct statfs64 *fsbuf, int fd);
/* Return information about the filesystem on which FD resides. */
@@ -60,12 +60,8 @@ __fstatvfs64 (int fd, struct statvfs64 *buf)
#endif
if (res == 0)
- {
- /* Convert the result. */
- struct stat64 st;
- __internal_statvfs64 (NULL, buf, &fsbuf,
- fstat64 (fd, &st) == -1 ? NULL : &st);
- }
+ /* Convert the result. */
+ __internal_statvfs64 (NULL, buf, &fsbuf, fd);
return res;
}
@@ -43,9 +43,11 @@
# ifndef __ASSUME_STATFS_F_FLAGS
int
-__statvfs_getflags (const char *name, int fstype, struct stat64 *st)
+__statvfs_getflags (const char *name, int fstype, int fd)
{
- if (st == NULL)
+ struct stat64 st;
+
+ if ((fd < 0 ? stat64 (name, &st) : fstat64 (fd, &st)) < 0)
return 0;
const char *fsname = NULL;
@@ -159,7 +161,7 @@ __statvfs_getflags (const char *name, int fstype, struct stat64 *st)
/* Find out about the device the current entry is for. */
struct stat64 fsst;
if (stat64 (mntbuf.mnt_dir, &fsst) >= 0
- && st->st_dev == fsst.st_dev)
+ && st.st_dev == fsst.st_dev)
{
/* Bingo, we found the entry for the device FD is on.
Now interpret the option string. */
@@ -222,14 +224,13 @@ __statvfs_getflags (const char *name, int fstype, struct stat64 *st)
}
# endif
#else
-extern int __statvfs_getflags (const char *name, int fstype,
- struct stat64 *st);
+extern int __statvfs_getflags (const char *name, int fstype, int fd);
#endif
void
INTERNAL_STATVFS (const char *name, struct STATVFS *buf,
- struct STATFS *fsbuf, struct stat64 *st)
+ struct STATFS *fsbuf, int fd)
{
/* Now fill in the fields we have information for. */
buf->f_bsize = fsbuf->f_bsize;
@@ -272,7 +273,7 @@ INTERNAL_STATVFS (const char *name, struct STATVFS *buf,
the /etc/mtab file and search for the entry which matches the given
file. The way we can test for matching filesystem is using the
device number. */
- buf->f_flag = __statvfs_getflags (name, fsbuf->f_type, st);
+ buf->f_flag = __statvfs_getflags (name, fsbuf->f_type, fd);
else
#endif
buf->f_flag = fsbuf->f_flags ^ ST_VALID;
@@ -22,22 +22,20 @@
#include <sys/statvfs.h>
extern void __internal_statvfs (const char *name, struct statvfs *buf,
- struct statfs *fsbuf, struct stat64 *st);
+ struct statfs *fsbuf, int fd);
int
statvfs (const char *file, struct statvfs *buf)
{
struct statfs fsbuf;
- struct stat64 st;
/* Get as much information as possible from the system. */
if (__statfs (file, &fsbuf) < 0)
return -1;
/* Convert the result. */
- __internal_statvfs (file, buf, &fsbuf,
- stat64 (file, &st) == -1 ? NULL : &st);
+ __internal_statvfs (file, buf, &fsbuf, -1);
/* We signal success if the statfs call succeeded. */
return 0;
@@ -26,7 +26,7 @@
extern void __internal_statvfs64 (const char *name, struct statvfs64 *buf,
- struct statfs64 *fsbuf, struct stat64 *st);
+ struct statfs64 *fsbuf, int fd);
/* Return information about the filesystem on which FILE resides. */
@@ -61,12 +61,8 @@ __statvfs64 (const char *file, struct statvfs64 *buf)
#endif
if (res == 0)
- {
- /* Convert the result. */
- struct stat64 st;
- __internal_statvfs64 (file, buf, &fsbuf,
- stat64 (file, &st) == -1 ? NULL : &st);
- }
+ /* Convert the result. */
+ __internal_statvfs64 (file, buf, &fsbuf, -1);
return res;
}