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Date: Sun, 5 Jan 2014 08:46:31 +0200
From: Baruch Siach <baruch@...s.co.il>
To: Theodore Ts'o <tytso@....edu>
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e4defrag: choose the best available posix_fadvise variant
Hi Ted,
On Sun, Jan 05, 2014 at 01:12:33AM -0500, Theodore Ts'o wrote:
> On Fri, Jan 03, 2014 at 11:23:44AM -0500, Theodore Ts'o wrote:
> >
> > Oh, oops. I'll find the other version of the patch and fix it up.
>
> Here is the revised version of your patch which I currently have in my
> sources. Let me know what you think.
Thanks. A few comments below.
> commit e47e7100a357ed9ba1575a6a8caca9258b1aab77
> Author: Baruch Siach <baruch@...s.co.il>
> Date: Thu Jan 2 13:05:37 2014 -0500
>
> e4defrag: choose the best available posix_fadvise variant
>
> Use posix_fadvise64() when available. This allows 64bit offsets on 32bit
> systems.
>
> Rename the internal posix_fadvise() implementation to avoid collision with the
> C library signature that is sometimes present event when the implementation
> itself is not. This fixes build errors like:
This paragraph is not needed anymore, since the internal posix_fadvise is
completely removed.
>
> e4defrag.c:189:2: warning: #warning Using locally defined posix_fadvise interface. [-Wcpp
> e4defrag.c:203:12: error: conflicting types for ‘posix_fadvise’
>
> [ Modified by tytso to try to use fadvise64 as well, and to remove the
> attempt to use the syscall directly, since between fadvise64,
> fadvise64_64, and complexities caused by required dummy arguments on
> some architectures, it's not worth the hair. ]
>
> Signed-off-by: Baruch Siach <baruch@...s.co.il>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
>
> diff --git a/configure b/configure
> index 6f8f1ab..5943849 100755
> --- a/configure
> +++ b/configure
> @@ -11051,7 +11051,7 @@ if test "$ac_res" != no; then :
> fi
>
> fi
> -for ac_func in __secure_getenv backtrace blkid_probe_get_topology chflags fallocate fallocate64 fchown fdatasync fstat64 ftruncate64 futimes getdtablesize getmntinfo getpwuid_r getrlimit getrusage jrand48 llseek lseek64 mallinfo mbstowcs memalign mmap msync nanosleep open64 pathconf posix_fadvise posix_memalign prctl secure_getenv setmntent setresgid setresuid srandom strcasecmp strdup strnlen strptime strtoull sync_file_range sysconf usleep utime valloc
> +for ac_func in __secure_getenv backtrace blkid_probe_get_topology chflags fadvise64 fallocate fallocate64 fchown fdatasync fstat64 ftruncate64 futimes getdtablesize getmntinfo getpwuid_r getrlimit getrusage jrand48 llseek lseek64 mallinfo mbstowcs memalign mmap msync nanosleep open64 pathconf posix_fadvise posix_fadvise64 posix_memalign prctl secure_getenv setmntent setresgid setresuid srandom strcasecmp strdup strnlen strptime strtoull sync_file_range sysconf usleep utime valloc
> do :
> as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
> ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
> diff --git a/configure.in b/configure.in
> index b70a3f9..214d3f6 100644
> --- a/configure.in
> +++ b/configure.in
> @@ -1026,6 +1026,7 @@ AC_CHECK_FUNCS(m4_flatten([
> backtrace
> blkid_probe_get_topology
> chflags
> + fadvise64
There is no such symbol in any C library that I know of (unlike fallocate64).
Where have you see this?
> fallocate
> fallocate64
> fchown
> @@ -1050,6 +1051,7 @@ AC_CHECK_FUNCS(m4_flatten([
> open64
> pathconf
> posix_fadvise
> + posix_fadvise64
> posix_memalign
> prctl
> secure_getenv
> diff --git a/lib/config.h.in b/lib/config.h.in
> index ef2e664..0197b56 100644
> --- a/lib/config.h.in
> +++ b/lib/config.h.in
> @@ -103,6 +103,9 @@
> /* Define to 1 if Ext2 ioctls present */
> #undef HAVE_EXT2_IOCTLS
>
> +/* Define to 1 if you have the `fadvise64' function. */
> +#undef HAVE_FADVISE64
> +
> /* Define to 1 if you have the `fallocate' function. */
> #undef HAVE_FALLOCATE
>
> @@ -287,6 +290,9 @@
> /* Define to 1 if you have the `posix_fadvise' function. */
> #undef HAVE_POSIX_FADVISE
>
> +/* Define to 1 if you have the `posix_fadvise64' function. */
> +#undef HAVE_POSIX_FADVISE64
> +
> /* Define to 1 if you have the `posix_memalign' function. */
> #undef HAVE_POSIX_MEMALIGN
>
> diff --git a/misc/e4defrag.c b/misc/e4defrag.c
> index c6a5f0d..65933b1 100644
> --- a/misc/e4defrag.c
> +++ b/misc/e4defrag.c
> @@ -34,13 +34,11 @@
> #include <unistd.h>
> #include <ext2fs/ext2_types.h>
> #include <ext2fs/ext2fs.h>
> -#include <linux/fs.h>
> #include <sys/ioctl.h>
> #include <ext2fs/fiemap.h>
> #include <sys/mman.h>
> #include <sys/stat.h>
> #include <sys/statfs.h>
> -#include <sys/syscall.h>
> #include <sys/vfs.h>
>
> /* A relatively new ioctl interface ... */
> @@ -183,28 +181,21 @@ static ext4_fsblk_t files_block_count;
> static struct frag_statistic_ino frag_rank[SHOW_FRAG_FILES];
>
>
> -/* Local definitions of some syscalls glibc may not yet have */
> -
> -#ifndef HAVE_POSIX_FADVISE
> -#warning Using locally defined posix_fadvise interface.
> -
> -#ifndef __NR_fadvise64_64
> -#error Your kernel headers dont define __NR_fadvise64_64
> -#endif
> -
> -/*
> - * fadvise() - Give advice about file access.
> +/* Local definitions of some syscalls glibc may not yet have
This comment becomes redundant. We now rely on the C library to provide the
system call.
> *
> - * @fd: defrag target file's descriptor.
> - * @offset: file offset.
> - * @len: area length.
> - * @advise: process flag.
> + * We prefer posix_fadvise64 when available, as it allows 64bit offset on
> + * 32bit systems
> */
> -static int posix_fadvise(int fd, loff_t offset, size_t len, int advise)
> -{
> - return syscall(__NR_fadvise64_64, fd, offset, len, advise);
> -}
> -#endif /* ! HAVE_FADVISE64_64 */
> +
> +#if defined(HAVE_POSIX_FADVISE64)
> +#define posix_fadvise posix_fadvise64
> +#elif defined(HAVE_FADVISE64)
> +#define posix_fadvise fadvise64
> +#elif defined(HAVE_POSIX_FADVISE)
> +#define posix_fadvise posix_fadvise
Also not needed.
> +#else
> +#error posix_fadvise not available!
> +#endif
>
> #ifndef HAVE_SYNC_FILE_RANGE
> #warning Using locally defined sync_file_range interface.
baruch
--
http://baruch.siach.name/blog/ ~. .~ Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
- baruch@...s.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -
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