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 <normalper...@yhbt.net> wrote: > Paul Eggert <egg...@cs.ucla.edu> 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 <normalper...@yhbt.net> 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
