path: root/arch/mips
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authorChristoph Hellwig <hch@lst.de>2009-10-27 11:05:28 +0100
committerJan Kara <jack@suse.cz>2009-12-10 15:02:50 +0100
commit6b2f3d1f769be5779b479c37800229d9a4809fc3 (patch)
tree046ef6736ec6c25ab1c68741ba715d13645af336 /arch/mips
parent59bc055211b8d266ab6089158058bf8268e02006 (diff)
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: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Kyle McMartin <kyle@mcmartin.ca> Acked-by: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'arch/mips')
4 files changed, 19 insertions, 3 deletions
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_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);