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[PATCH] avoid stat/fstat in statvfs/fstatvfs
From: |
Eric Wong |
Subject: |
[PATCH] avoid stat/fstat in statvfs/fstatvfs |
Date: |
Fri, 1 Feb 2013 02:35:10 +0000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
It turns out this problem was not specific to eglibc or Debian.
glibc has the same issue with stat() being called in statvfs() on
Linux 2.6.36+
Eric Wong <address@hidden> wrote:
> Paul Eggert <address@hidden> wrote:
> > On 01/29/2013 06:44 PM, Eric Wong wrote:
> > > eglibc on Debian is only configured to only use features available in
> > > Linux 2.6.26 at build time. This means statvfs() uses stat() internally
> > > regardless of the run-time kernel version[1].
> >
> > That sounds like a bug in eglibc. Perhaps you can fix this problem on the
> > eglibc side. That is, eglibc can use only 2.6.26 features, but make an
> > exception for this feature, since it's obviously needed.
>
> Actually, reading the eglibc and kernel source more closely, my initial
> analysis seems wrong, and I'm even more at a loss as to why stat()
> gets called when I call statvfs().
I completely missed the stat() calls inside the __internal_statvfs()
argument list :x
> The stat() I see after statfs() is /not/ happening from a check of
> where the 2.6.36+ kernel sets ST_VALID:
>
> At first, I thought the following code was entering __statvfs_getflags()
> in sysdeps/unix/sysv/linux/internal_statvfs.c:
>
> #ifndef __ASSUME_STATFS_F_FLAGS
> if ((fsbuf->f_flags & ST_VALID) == 0)
> /* Determining the flags is tricky. We have to read /proc/mounts or
> 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);
> else
> #endif
> buf->f_flag = fsbuf->f_flags ^ ST_VALID;
> -----------------------------------------------------------------
> But now I see it's not, since __statvfs_getflags() would also
> open /proc/mounts (which I don't see happening).
>
> Anyways I've filed a bug report with Debian:
> http://bugs.debian.org/699321
>
> Thanks for looking at this, hopefully somebody from Debian can help.
>From 2374682f5dc38d7cc752cdbdecd55bd870b38a90 Mon Sep 17 00:00:00 2001
From: Eric Wong <address@hidden>
Date: Fri, 1 Feb 2013 01:55:27 +0000
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.
---
sysdeps/unix/sysv/linux/fstatvfs.c | 4 ++--
sysdeps/unix/sysv/linux/fstatvfs64.c | 10 +++-------
sysdeps/unix/sysv/linux/internal_statvfs.c | 16 +++++++++-------
sysdeps/unix/sysv/linux/statvfs.c | 6 ++----
sysdeps/unix/sysv/linux/statvfs64.c | 10 +++-------
5 files changed, 19 insertions(+), 27 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/fstatvfs.c
b/sysdeps/unix/sysv/linux/fstatvfs.c
index 8f08d14..6a03a87 100644
--- a/sysdeps/unix/sysv/linux/fstatvfs.c
+++ b/sysdeps/unix/sysv/linux/fstatvfs.c
@@ -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;
diff --git a/sysdeps/unix/sysv/linux/fstatvfs64.c
b/sysdeps/unix/sysv/linux/fstatvfs64.c
index 2dcef94..3b49ab2 100644
--- a/sysdeps/unix/sysv/linux/fstatvfs64.c
+++ b/sysdeps/unix/sysv/linux/fstatvfs64.c
@@ -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;
}
diff --git a/sysdeps/unix/sysv/linux/internal_statvfs.c
b/sysdeps/unix/sysv/linux/internal_statvfs.c
index 4cd4f04..cb9400e 100644
--- a/sysdeps/unix/sysv/linux/internal_statvfs.c
+++ b/sysdeps/unix/sysv/linux/internal_statvfs.c
@@ -43,9 +43,12 @@
# 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;
+ int r = fd >= 0 ? fstat64(fd, &st) : stat64(name, &st);
+
+ if (r == -1)
return 0;
const char *fsname = NULL;
@@ -153,7 +156,7 @@ __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. */
@@ -216,14 +219,13 @@ __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;
@@ -266,7 +268,7 @@ 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;
diff --git a/sysdeps/unix/sysv/linux/statvfs.c
b/sysdeps/unix/sysv/linux/statvfs.c
index 5d91d85..09b53f7 100644
--- a/sysdeps/unix/sysv/linux/statvfs.c
+++ b/sysdeps/unix/sysv/linux/statvfs.c
@@ -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;
diff --git a/sysdeps/unix/sysv/linux/statvfs64.c
b/sysdeps/unix/sysv/linux/statvfs64.c
index 42c1089..cd9a7ca 100644
--- a/sysdeps/unix/sysv/linux/statvfs64.c
+++ b/sysdeps/unix/sysv/linux/statvfs64.c
@@ -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;
}
--
Eric Wong