From 6b2f3d1f769be5779b479c37800229d9a4809fc3 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 27 Oct 2009 11:05:28 +0100 Subject: 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 Cc: Ivan Kokshaysky Cc: Grant Grundler Cc: "David S. Miller" Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Thomas Gleixner Cc: Al Viro Cc: Andreas Dilger Acked-by: Trond Myklebust Acked-by: Kyle McMartin Acked-by: Ulrich Drepper Signed-off-by: Christoph Hellwig Signed-off-by: Andrew Morton Signed-off-by: Jan Kara --- arch/mips/include/asm/fcntl.h | 17 ++++++++++++++++- arch/mips/kernel/kspd.c | 1 + arch/mips/loongson/common/mem.c | 2 +- arch/mips/mm/cache.c | 2 +- 4 files changed, 19 insertions(+), 3 deletions(-) (limited to 'arch/mips') diff --git a/arch/mips/include/asm/fcntl.h b/arch/mips/include/asm/fcntl.h index 2a52333a062d..7c6681aa2ab8 100644 --- a/arch/mips/include/asm/fcntl.h +++ b/arch/mips/include/asm/fcntl.h @@ -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 diff --git a/arch/mips/kernel/kspd.c b/arch/mips/kernel/kspd.c index ad4e017ed2f3..80e2ba694bab 100644 --- a/arch/mips/kernel/kspd.c +++ b/arch/mips/kernel/kspd.c @@ -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 diff --git a/arch/mips/loongson/common/mem.c b/arch/mips/loongson/common/mem.c index 7c92f79b6480..e94ef158f980 100644 --- a/arch/mips/loongson/common/mem.c +++ b/arch/mips/loongson/common/mem.c @@ -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) || diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c index 694d51f523d1..102b2dfa542a 100644 --- a/arch/mips/mm/cache.c +++ b/arch/mips/mm/cache.c @@ -194,7 +194,7 @@ void __devinit cpu_cache_init(void) int __weak __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); -- cgit v1.2.2