From 4e5f31c847982997c856f03bbc35134e9fd0f61f Mon Sep 17 00:00:00 2001 From: Ulrich Drepper Date: Thu, 7 Jul 2011 10:53:16 -0400 Subject: [PATCH] Handle ext4 in {,f}pathconf ext4 has a higher LINK_MAX limit than ext2/3. Unfortunately it is not easy to distinguish the filesystems from userlevel. --- ChangeLog | 10 ++++ sysdeps/unix/sysv/linux/fpathconf.c | 4 +- sysdeps/unix/sysv/linux/pathconf.c | 83 +++++++++++++++++++++++++++-- sysdeps/unix/sysv/linux/pathconf.h | 9 ++-- 4 files changed, 97 insertions(+), 9 deletions(-) diff --git a/ChangeLog b/ChangeLog index 6225871c2b..050bff3499 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,15 @@ 2011-07-07 Ulrich Drepper + * sysdeps/unix/sysv/linux/pathconf.c (distinguish_extX): New function. + (__statfs_link_max): Use it to dostinguish between ext2/3 and ext4. + The latter has a higher limit. Take additional parameter to pass to + the new function. + (__pathconf): Pass file to __statfs_link_max. + * sysdeps/unix/sysv/linux/fpathconf.c (__fpathconf): Pass fd to + __statfs_link_max. + * sysdeps/unix/sysv/linux/pathconf.h: Adjust prototype of + __statfs_link_max. + [BZ #12868] * sysdeps/unix/sysv/linux/linux_fsinfo.h: Define Lustre constants. * sysdeps/unix/sysv/linux/internal_statvfs.c (__statvfs_getflags): diff --git a/sysdeps/unix/sysv/linux/fpathconf.c b/sysdeps/unix/sysv/linux/fpathconf.c index 617a5a93cf..12a1e3221e 100644 --- a/sysdeps/unix/sysv/linux/fpathconf.c +++ b/sysdeps/unix/sysv/linux/fpathconf.c @@ -1,5 +1,5 @@ /* Get file-specific information about descriptor FD. Linux version. - Copyright (C) 1991,1995,1996,1998-2003,2008,2010 + Copyright (C) 1991,1995,1996,1998-2003,2008,2010,2011 Free Software Foundation, Inc. This file is part of the GNU C Library. @@ -40,7 +40,7 @@ __fpathconf (fd, name) switch (name) { case _PC_LINK_MAX: - return __statfs_link_max (__fstatfs (fd, &fsbuf), &fsbuf); + return __statfs_link_max (__fstatfs (fd, &fsbuf), &fsbuf, NULL, fd); case _PC_FILESIZEBITS: return __statfs_filesize_max (__fstatfs (fd, &fsbuf), &fsbuf); diff --git a/sysdeps/unix/sysv/linux/pathconf.c b/sysdeps/unix/sysv/linux/pathconf.c index 42b7b80c39..185931404b 100644 --- a/sysdeps/unix/sysv/linux/pathconf.c +++ b/sysdeps/unix/sysv/linux/pathconf.c @@ -17,8 +17,11 @@ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ -#include #include +#include +#include +#include +#include #include "pathconf.h" #include "linux_fsinfo.h" @@ -42,7 +45,7 @@ __pathconf (const char *file, int name) switch (name) { case _PC_LINK_MAX: - return __statfs_link_max (__statfs (file, &fsbuf), &fsbuf); + return __statfs_link_max (__statfs (file, &fsbuf), &fsbuf, file, -1); case _PC_FILESIZEBITS: return __statfs_filesize_max (__statfs (file, &fsbuf), &fsbuf); @@ -74,9 +77,77 @@ __pathconf (const char *file, int name) } +static long int +distinguish_extX (const struct statfs *fsbuf, const char *file, int fd) +{ + char buf[64]; + char path[PATH_MAX]; + struct stat64 st; + + if ((file == NULL ? fstat64 (fd, &st) : stat64 (file, &st)) != 0) + /* Strange. The statfd call worked, but stat fails. Default to + the more pessimistic value. */ + return EXT2_LINK_MAX; + + __snprintf (buf, sizeof (buf), "/sys/dev/block/%u:%u", + gnu_dev_major (st.st_dev), gnu_dev_minor (st.st_dev)); + + ssize_t n = __readlink (buf, path, sizeof (path)); + if (n != -1 && n < sizeof (path)) + { + path[n] = '\0'; + char *base = strdupa (basename (path)); + __snprintf (path, sizeof (path), "/sys/fs/ext4/%s", base); + + return __access (path, F_OK) == 0 ? EXT4_LINK_MAX : EXT2_LINK_MAX; + } + + /* XXX Is there a better way to distinguish ext2/3 from ext4 than + iterating over the mounted filesystems and compare the device + numbers? */ + FILE *mtab = __setmntent ("/proc/mounts", "r"); + if (mtab == NULL) + mtab = __setmntent (_PATH_MOUNTED, "r"); + + /* By default be conservative. */ + long int result = EXT2_LINK_MAX; + if (mtab != NULL) + { + struct mntent mntbuf; + char tmpbuf[1024]; + + /* No locking needed. */ + (void) __fsetlocking (mtab, FSETLOCKING_BYCALLER); + + while (__getmntent_r (mtab, &mntbuf, tmpbuf, sizeof (tmpbuf))) + { + if (strcmp (mntbuf.mnt_type, "ext2") != 0 + && strcmp (mntbuf.mnt_type, "ext3") != 0 + && strcmp (mntbuf.mnt_type, "ext4") != 0) + continue; + + struct stat64 fsst; + if (stat64 (mntbuf.mnt_dir, &fsst) >= 0 + && st.st_dev == fsst.st_dev) + { + if (strcmp (mntbuf.mnt_type, "ext4") == 0) + result = EXT4_LINK_MAX; + break; + } + } + + /* Close the file. */ + __endmntent (mtab); + } + + return result; +} + + /* Used like: return statfs_link_max (__statfs (name, &buf), &buf); */ long int -__statfs_link_max (int result, const struct statfs *fsbuf) +__statfs_link_max (int result, const struct statfs *fsbuf, const char *file, + int fd) { if (result < 0) { @@ -91,7 +162,11 @@ __statfs_link_max (int result, const struct statfs *fsbuf) switch (fsbuf->f_type) { case EXT2_SUPER_MAGIC: - return EXT2_LINK_MAX; + /* Unfortunately the kernel does not return a different magic number + for ext4. This would be necessary to easily detect etx4 since it + has a different LINK_MAX value. Therefore we have to find it out + the hard way. */ + return distinguish_extX (fsbuf, file, fd); case MINIX_SUPER_MAGIC: case MINIX_SUPER_MAGIC2: diff --git a/sysdeps/unix/sysv/linux/pathconf.h b/sysdeps/unix/sysv/linux/pathconf.h index 806adcc5ea..34289d8005 100644 --- a/sysdeps/unix/sysv/linux/pathconf.h +++ b/sysdeps/unix/sysv/linux/pathconf.h @@ -1,5 +1,6 @@ /* Common parts of Linux implementation of pathconf and fpathconf. - Copyright (C) 1991,1995,1996,1998-2003,2008 Free Software Foundation, Inc. + Copyright (C) 1991,1995,1996,1998-2003,2008,2011 + Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -22,8 +23,10 @@ #include -/* Used like: return __statfs_link_max (__statfs (name, &buf), &buf); */ -extern long int __statfs_link_max (int result, const struct statfs *fsbuf); +/* Used like: return __statfs_link_max (__statfs (name, &buf), &buf, + name, -1); */ +extern long int __statfs_link_max (int result, const struct statfs *fsbuf, + const char *file, int fd); /* Used like: return __statfs_filesize_max (__statfs (name, &buf), &buf); */ -- 2.43.5