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Commit 6b2f3d1f authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jan Kara
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vfs: Implement proper O_SYNC semantics 



While Linux provided an O_SYNC flag basically since day 1, it took until
Linux 2.4.0-test12pre2 to actually get it implemented for filesystems,
since that day we had generic_osync_around with only minor changes and the
great "For now, when the user asks for O_SYNC, we'll actually give
O_DSYNC" comment.  This patch intends to actually give us real O_SYNC
semantics in addition to the O_DSYNC semantics.  After Jan's O_SYNC
patches which are required before this patch it's actually surprisingly
simple, we just need to figure out when to set the datasync flag to
vfs_fsync_range and when not.

This patch renames the existing O_SYNC flag to O_DSYNC while keeping it's
numerical value to keep binary compatibility, and adds a new real O_SYNC
flag.  To guarantee backwards compatiblity it is defined as expanding to
both the O_DSYNC and the new additional binary flag (__O_SYNC) to make
sure we are backwards-compatible when compiled against the new headers.

This also means that all places that don't care about the differences can
just check O_DSYNC and get the right behaviour for O_SYNC, too - only
places that actuall care need to check __O_SYNC in addition.  Drivers and
network filesystems have been updated in a fail safe way to always do the
full sync magic if O_DSYNC is set.  The few places setting O_SYNC for
lower layers are kept that way for now to stay failsafe.

We enforce that O_DSYNC is set when __O_SYNC is set early in the open path
to make sure we always get these sane options.

Note that parisc really screwed up their headers as they already define a
O_DSYNC that has always been a no-op.  We try to repair it by using it for
the new O_DSYNC and redefinining O_SYNC to send both the traditional
O_SYNC numerical value _and_ the O_DSYNC one.

Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Grant Grundler <grundler@parisc-linux.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Dilger <adilger@sun.com>
Acked-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: default avatarKyle McMartin <kyle@mcmartin.ca>
Acked-by: default avatarUlrich Drepper <drepper@redhat.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 59bc0552

arch/alpha/include/asm/fcntl.h

+16 −3
Original line number Diff line number Diff line 
#ifndef _ALPHA_FCNTL_H

#define _ALPHA_FCNTL_H



/* open/fcntl - O_SYNC is only implemented on blocks devices and on files

   located on an ext2 file system */

#define O_CREAT		 01000	/* not fcntl */

#define O_TRUNC		 02000	/* not fcntl */

#define O_EXCL		 04000	/* not fcntl */
@@ -10,13 +8,28 @@ 


#define O_NONBLOCK	 00004

#define O_APPEND	 00010

#define O_SYNC		040000

#define O_DSYNC		040000	/* used to be O_SYNC, see below */

#define O_DIRECTORY	0100000	/* must be a directory */

#define O_NOFOLLOW	0200000 /* don't follow links */

#define O_LARGEFILE	0400000 /* will be set by the kernel on every open */

#define O_DIRECT	02000000 /* direct disk access - should check with OSF/1 */

#define O_NOATIME	04000000

#define O_CLOEXEC	010000000 /* set close_on_exec */

/*

 * Before Linux 2.6.32 only O_DSYNC semantics were implemented, but using

 * the O_SYNC flag.  We continue to use the existing numerical value

 * for O_DSYNC semantics now, but using the correct symbolic name for it.

 * This new value is used to request true Posix O_SYNC semantics.  It is

 * defined in this strange way to make sure applications compiled against

 * new headers get at least O_DSYNC semantics on older kernels.

 *

 * This has the nice side-effect that we can simply test for O_DSYNC

 * wherever we do not care if O_DSYNC or O_SYNC is used.

 *

 * Note: __O_SYNC must never be used directly.

 */

#define __O_SYNC	020000000

#define O_SYNC		(__O_SYNC|O_DSYNC)



#define F_GETLK		7

#define F_SETLK		8

arch/blackfin/include/asm/fcntl.h

+0 −2
Original line number Diff line number Diff line
@@ -7,8 +7,6 @@ 
#ifndef _BFIN_FCNTL_H

#define _BFIN_FCNTL_H



/* open/fcntl - O_SYNC is only implemented on blocks devices and on files

   located on an ext2 file system */

#define O_DIRECTORY	 040000	/* must be a directory */

#define O_NOFOLLOW	0100000	/* don't follow links */

#define O_DIRECT	0200000	/* direct disk access hint - currently ignored */

arch/mips/include/asm/fcntl.h

+16 −1
Original line number Diff line number Diff line
@@ -10,7 +10,7 @@ 




#define O_APPEND	0x0008

#define O_SYNC		0x0010

#define O_DSYNC		0x0010	/* used to be O_SYNC, see below */

#define O_NONBLOCK	0x0080

#define O_CREAT         0x0100	/* not fcntl */

#define O_TRUNC		0x0200	/* not fcntl */
@@ -18,6 +18,21 @@ 
#define O_NOCTTY	0x0800	/* not fcntl */

#define FASYNC		0x1000	/* fcntl, for BSD compatibility */

#define O_LARGEFILE	0x2000	/* allow large file opens */

/*

 * Before Linux 2.6.32 only O_DSYNC semantics were implemented, but using

 * the O_SYNC flag.  We continue to use the existing numerical value

 * for O_DSYNC semantics now, but using the correct symbolic name for it.

 * This new value is used to request true Posix O_SYNC semantics.  It is

 * defined in this strange way to make sure applications compiled against

 * new headers get at least O_DSYNC semantics on older kernels.

 *

 * This has the nice side-effect that we can simply test for O_DSYNC

 * wherever we do not care if O_DSYNC or O_SYNC is used.

 *

 * Note: __O_SYNC must never be used directly.

 */

#define __O_SYNC	0x4000

#define O_SYNC		(__O_SYNC|O_DSYNC)

#define O_DIRECT	0x8000	/* direct disk access hint */



#define F_GETLK		14

arch/mips/kernel/kspd.c

+1 −0
Original line number Diff line number Diff line
@@ -82,6 +82,7 @@ static int sp_stopping; 
#define MTSP_O_SHLOCK		0x0010

#define MTSP_O_EXLOCK		0x0020

#define MTSP_O_ASYNC		0x0040

/* XXX: check which of these is actually O_SYNC vs O_DSYNC */

#define MTSP_O_FSYNC		O_SYNC

#define MTSP_O_NOFOLLOW		0x0100

#define MTSP_O_SYNC		0x0080

arch/mips/loongson/common/mem.c

+1 −1
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ void __init prom_init_memory(void) 
/* override of arch/mips/mm/cache.c: __uncached_access */

int __uncached_access(struct file *file, unsigned long addr)

{

	if (file->f_flags & O_SYNC)

	if (file->f_flags & O_DSYNC)

		return 1;



	return addr >= __pa(high_memory) ||