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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/alpha
parent59bc055211b8d266ab6089158058bf8268e02006 (diff)
downloadlinux-stericsson-6b2f3d1f769be5779b479c37800229d9a4809fc3.tar.gz
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/alpha')
-rw-r--r--arch/alpha/include/asm/fcntl.h19
1 files changed, 16 insertions, 3 deletions
diff --git a/arch/alpha/include/asm/fcntl.h b/arch/alpha/include/asm/fcntl.h
index 25da0017ec87..21b1117a0c61 100644
--- a/arch/alpha/include/asm/fcntl.h
+++ b/arch/alpha/include/asm/fcntl.h
@@ -1,8 +1,6 @@
#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