Re: [PATCH] implement posix O_SYNC and O_DSYNC semantics

From: Jan Kara
Date: Tue Sep 15 2009 - 10:11:12 EST

On Tue 15-09-09 15:12:52, Christoph Hellwig wrote:
> 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 fucked 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.
>
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Acked-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
The patch looks fine now.
Acked-by: Jan Kara <jack@xxxxxxx>

> Index: linux-2.6/arch/x86/mm/pat.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/mm/pat.c 2009-09-15 00:46:32.911256267 -0300
> +++ linux-2.6/arch/x86/mm/pat.c 2009-09-15 09:41:27.301253948 -0300
> @@ -541,7 +541,7 @@ int phys_mem_access_prot_allowed(struct
> if (!range_is_allowed(pfn, size))
> return 0;
>
> - if (file->f_flags & O_SYNC) {
> + if (file->f_flags & O_DSYNC) {
> flags = _PAGE_CACHE_UC_MINUS;
> }
>
> Index: linux-2.6/drivers/char/mem.c
> ===================================================================
> --- linux-2.6.orig/drivers/char/mem.c 2009-09-15 00:46:33.096254330 -0300
> +++ linux-2.6/drivers/char/mem.c 2009-09-15 09:41:27.302253936 -0300
> @@ -44,7 +44,7 @@ static inline int uncached_access(struct
> {
> #if defined(CONFIG_IA64)
> /*
> - * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
> + * On ia64, we ignore O_DSYNC because we cannot tolerate memory attribute aliases.
> */
> return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
> #elif defined(CONFIG_MIPS)
> @@ -57,9 +57,9 @@ static inline int uncached_access(struct
> #else
> /*
> * Accessing memory above the top the kernel knows about or through a file pointer
> - * that was marked O_SYNC will be done non-cached.
> + * that was marked O_DSYNC will be done non-cached.
> */
> - if (file->f_flags & O_SYNC)
> + if (file->f_flags & O_DSYNC)
> return 1;
> return addr >= __pa(high_memory);
> #endif
> Index: linux-2.6/drivers/staging/me4000/me4000.c
> ===================================================================
> --- linux-2.6.orig/drivers/staging/me4000/me4000.c 2009-09-15 00:46:33.130254399 -0300
> +++ linux-2.6/drivers/staging/me4000/me4000.c 2009-09-15 09:41:27.305253618 -0300
> @@ -1985,8 +1985,8 @@ static ssize_t me4000_ao_write_cont(stru
> spin_unlock_irqrestore(&ao_context->int_lock, flags);
> }
>
> - /* Wait until the state machine is stopped if O_SYNC is set */
> - if (filep->f_flags & O_SYNC) {
> + /* Wait until the state machine is stopped if O_DSYNC is set */
> + if (filep->f_flags & O_DSYNC) {
> while (inl(ao_context->status_reg) &
> ME4000_AO_STATUS_BIT_FSM) {
> interruptible_sleep_on_timeout(&queue, 1);
> Index: linux-2.6/drivers/usb/gadget/file_storage.c
> ===================================================================
> --- linux-2.6.orig/drivers/usb/gadget/file_storage.c 2009-09-15 00:46:33.138253951 -0300
> +++ linux-2.6/drivers/usb/gadget/file_storage.c 2009-09-15 09:41:27.311253752 -0300
> @@ -1713,7 +1713,7 @@ static int do_write(struct fsg_dev *fsg)
> }
> if (fsg->cmnd[1] & 0x08) { // FUA
> spin_lock(&curlun->filp->f_lock);
> - curlun->filp->f_flags |= O_SYNC;
> + curlun->filp->f_flags |= O_DSYNC;
> spin_unlock(&curlun->filp->f_lock);
> }
> }
> Index: linux-2.6/fs/afs/write.c
> ===================================================================
> --- linux-2.6.orig/fs/afs/write.c 2009-09-15 00:46:33.144254016 -0300
> +++ linux-2.6/fs/afs/write.c 2009-09-15 09:41:27.316253550 -0300
> @@ -692,8 +692,9 @@ ssize_t afs_file_write(struct kiocb *ioc
> }
>
> /* return error values for O_SYNC and IS_SYNC() */
> - if (IS_SYNC(&vnode->vfs_inode) || iocb->ki_filp->f_flags & O_SYNC) {
> - ret = afs_fsync(iocb->ki_filp, dentry, 1);
> + if (IS_SYNC(&vnode->vfs_inode) || iocb->ki_filp->f_flags & O_DSYNC) {
> + ret = afs_fsync(iocb->ki_filp, dentry,
> + (iocb->ki_filp->f_flags & __O_SYNC) ? 0 : 1);
> if (ret < 0)
> result = ret;
> }
> Index: linux-2.6/fs/btrfs/file.c
> ===================================================================
> --- linux-2.6.orig/fs/btrfs/file.c 2009-09-15 00:46:33.151254279 -0300
> +++ linux-2.6/fs/btrfs/file.c 2009-09-15 09:41:27.316253550 -0300
> @@ -924,7 +924,7 @@ static ssize_t btrfs_file_write(struct f
> unsigned long last_index;
> int will_write;
>
> - will_write = ((file->f_flags & O_SYNC) || IS_SYNC(inode) ||
> + will_write = ((file->f_flags & O_DSYNC) || IS_SYNC(inode) ||
> (file->f_flags & O_DIRECT));
>
> nrptrs = min((count + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE,
> @@ -1077,7 +1077,7 @@ out_nolock:
> if (err)
> num_written = err;
>
> - if ((file->f_flags & O_SYNC) || IS_SYNC(inode)) {
> + if ((file->f_flags & O_DSYNC) || IS_SYNC(inode)) {
> trans = btrfs_start_transaction(root, 1);
> ret = btrfs_log_dentry_safe(trans, root,
> file->f_dentry);
> Index: linux-2.6/fs/cifs/dir.c
> ===================================================================
> --- linux-2.6.orig/fs/cifs/dir.c 2009-09-15 00:46:33.156254147 -0300
> +++ linux-2.6/fs/cifs/dir.c 2009-09-15 09:41:27.319254141 -0300
> @@ -214,7 +214,8 @@ int cifs_posix_open(char *full_path, str
> posix_flags |= SMB_O_TRUNC;
> if (oflags & O_APPEND)
> posix_flags |= SMB_O_APPEND;
> - if (oflags & O_SYNC)
> + /* be safe and imply O_SYNC for O_DSYNC */
> + if (oflags & O_DSYNC)
> posix_flags |= SMB_O_SYNC;
> if (oflags & O_DIRECTORY)
> posix_flags |= SMB_O_DIRECTORY;
> Index: linux-2.6/fs/cifs/file.c
> ===================================================================
> --- linux-2.6.orig/fs/cifs/file.c 2009-09-15 00:46:33.162254422 -0300
> +++ linux-2.6/fs/cifs/file.c 2009-09-15 09:41:27.323254719 -0300
> @@ -96,8 +96,10 @@ static inline fmode_t cifs_posix_convert
> reopening a file. They had their effect on the original open */
> if (flags & O_APPEND)
> posix_flags |= (fmode_t)O_APPEND;
> - if (flags & O_SYNC)
> - posix_flags |= (fmode_t)O_SYNC;
> + if (flags & O_DSYNC)
> + posix_flags |= (fmode_t)O_DSYNC;
> + if (flags & __O_SYNC)
> + posix_flags |= (fmode_t)__O_SYNC;
> if (flags & O_DIRECTORY)
> posix_flags |= (fmode_t)O_DIRECTORY;
> if (flags & O_NOFOLLOW)
> Index: linux-2.6/fs/namei.c
> ===================================================================
> --- linux-2.6.orig/fs/namei.c 2009-09-15 00:46:33.168253161 -0300
> +++ linux-2.6/fs/namei.c 2009-09-15 09:45:26.694256679 -0300
> @@ -1678,6 +1678,15 @@ struct file *do_filp_open(int dfd, const
> int will_write;
> int flag = open_to_namei_flags(open_flag);
>
> + /*
> + * O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
> + * check for O_DSYNC if the need any syncing at all we enforce it's
> + * always set instead of having to deal with possibly weird behaviour
> + * for malicious applications setting only __O_SYNC.
> + */
> + if (open_flag & __O_SYNC)
> + open_flag |= O_DSYNC;
> +
> if (!acc_mode)
> acc_mode = MAY_OPEN | ACC_MODE(flag);
>
> Index: linux-2.6/fs/nfs/file.c
> ===================================================================
> --- linux-2.6.orig/fs/nfs/file.c 2009-09-15 00:46:33.174254134 -0300
> +++ linux-2.6/fs/nfs/file.c 2009-09-15 09:41:27.330253653 -0300
> @@ -580,7 +580,7 @@ static int nfs_need_sync_write(struct fi
> {
> struct nfs_open_context *ctx;
>
> - if (IS_SYNC(inode) || (filp->f_flags & O_SYNC))
> + if (IS_SYNC(inode) || (filp->f_flags & O_DSYNC))
> return 1;
> ctx = nfs_file_open_context(filp);
> if (test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags))
> @@ -621,7 +621,7 @@ static ssize_t nfs_file_write(struct kio
>
> nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, count);
> result = generic_file_aio_write(iocb, iov, nr_segs, pos);
> - /* Return error values for O_SYNC and IS_SYNC() */
> + /* Return error values for O_DSYNC and IS_SYNC() */
> if (result >= 0 && nfs_need_sync_write(iocb->ki_filp, inode)) {
> int err = nfs_do_fsync(nfs_file_open_context(iocb->ki_filp), inode);
> if (err < 0)
> Index: linux-2.6/fs/nfs/write.c
> ===================================================================
> --- linux-2.6.orig/fs/nfs/write.c 2009-09-15 00:46:33.180254200 -0300
> +++ linux-2.6/fs/nfs/write.c 2009-09-15 09:41:27.332254187 -0300
> @@ -774,7 +774,7 @@ int nfs_updatepage(struct file *file, st
> */
> if (nfs_write_pageuptodate(page, inode) &&
> inode->i_flock == NULL &&
> - !(file->f_flags & O_SYNC)) {
> + !(file->f_flags & O_DSYNC)) {
> count = max(count + offset, nfs_page_length(page));
> offset = 0;
> }
> Index: linux-2.6/include/asm-generic/fcntl.h
> ===================================================================
> --- linux-2.6.orig/include/asm-generic/fcntl.h 2009-09-15 00:46:33.211253817 -0300
> +++ linux-2.6/include/asm-generic/fcntl.h 2009-09-15 09:41:27.335253940 -0300
> @@ -3,8 +3,6 @@
>
> #include <linux/types.h>
>
> -/* open/fcntl - O_SYNC is only implemented on blocks devices and on files
> - located on an ext2 file system */
> #define O_ACCMODE 00000003
> #define O_RDONLY 00000000
> #define O_WRONLY 00000001
> @@ -27,8 +25,8 @@
> #ifndef O_NONBLOCK
> #define O_NONBLOCK 00004000
> #endif
> -#ifndef O_SYNC
> -#define O_SYNC 00010000
> +#ifndef O_DSYNC
> +#define O_DSYNC 00010000 /* used to be O_SYNC, see below */
> #endif
> #ifndef FASYNC
> #define FASYNC 00020000 /* fcntl, for BSD compatibility */
> @@ -51,6 +49,25 @@
> #ifndef O_CLOEXEC
> #define O_CLOEXEC 02000000 /* set close_on_exec */
> #endif
> +
> +/*
> + * 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.
> + */
> +#ifndef O_SYNC
> +#define __O_SYNC 04000000
> +#define O_SYNC (__O_SYNC|O_DSYNC)
> +#endif
> +
> #ifndef O_NDELAY
> #define O_NDELAY O_NONBLOCK
> #endif
> Index: linux-2.6/fs/ocfs2/file.c
> ===================================================================
> --- linux-2.6.orig/fs/ocfs2/file.c 2009-09-15 00:46:33.186253776 -0300
> +++ linux-2.6/fs/ocfs2/file.c 2009-09-15 09:41:27.338254042 -0300
> @@ -1878,7 +1878,7 @@ out_dio:
> /* buffered aio wouldn't have proper lock coverage today */
> BUG_ON(ret == -EIOCBQUEUED && !(file->f_flags & O_DIRECT));
>
> - if ((file->f_flags & O_SYNC && !direct_io) || IS_SYNC(inode)) {
> + if ((file->f_flags & O_DSYNC && !direct_io) || IS_SYNC(inode)) {
> ret = filemap_fdatawrite_range(file->f_mapping, pos,
> pos + count - 1);
> if (ret < 0)
> Index: linux-2.6/fs/ubifs/file.c
> ===================================================================
> --- linux-2.6.orig/fs/ubifs/file.c 2009-09-15 00:46:33.192253912 -0300
> +++ linux-2.6/fs/ubifs/file.c 2009-09-15 09:41:27.341254213 -0300
> @@ -1403,7 +1403,7 @@ static ssize_t ubifs_aio_write(struct ki
> if (ret < 0)
> return ret;
>
> - if (ret > 0 && (IS_SYNC(inode) || iocb->ki_filp->f_flags & O_SYNC)) {
> + if (ret > 0 && (IS_SYNC(inode) || iocb->ki_filp->f_flags & O_DSYNC)) {
> err = ubifs_sync_wbufs_by_inode(c, inode);
> if (err)
> return err;
> Index: linux-2.6/fs/xfs/linux-2.6/xfs_lrw.c
> ===================================================================
> --- linux-2.6.orig/fs/xfs/linux-2.6/xfs_lrw.c 2009-09-15 00:46:33.198253488 -0300
> +++ linux-2.6/fs/xfs/linux-2.6/xfs_lrw.c 2009-09-15 09:41:27.344254176 -0300
> @@ -811,7 +811,7 @@ write_retry:
> XFS_STATS_ADD(xs_write_bytes, ret);
>
> /* Handle various SYNC-type writes */
> - if ((file->f_flags & O_SYNC) || IS_SYNC(inode)) {
> + if ((file->f_flags & O_DSYNC) || IS_SYNC(inode)) {
> int error2;
>
> xfs_iunlock(xip, iolock);
> Index: linux-2.6/sound/core/rawmidi.c
> ===================================================================
> --- linux-2.6.orig/sound/core/rawmidi.c 2009-09-15 00:46:33.219253718 -0300
> +++ linux-2.6/sound/core/rawmidi.c 2009-09-15 09:41:27.347253859 -0300
> @@ -1258,7 +1258,7 @@ static ssize_t snd_rawmidi_write(struct
> break;
> count -= count1;
> }
> - if (file->f_flags & O_SYNC) {
> + if (file->f_flags & O_DSYNC) {
> spin_lock_irq(&runtime->lock);
> while (runtime->avail != runtime->buffer_size) {
> wait_queue_t wait;
> Index: linux-2.6/arch/alpha/include/asm/fcntl.h
> ===================================================================
> --- linux-2.6.orig/arch/alpha/include/asm/fcntl.h 2009-09-15 00:46:32.945006724 -0300
> +++ linux-2.6/arch/alpha/include/asm/fcntl.h 2009-09-15 09:41:27.348253497 -0300
> @@ -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
> Index: linux-2.6/arch/blackfin/include/asm/fcntl.h
> ===================================================================
> --- linux-2.6.orig/arch/blackfin/include/asm/fcntl.h 2009-09-15 00:46:32.978006455 -0300
> +++ linux-2.6/arch/blackfin/include/asm/fcntl.h 2009-09-15 09:41:27.351254088 -0300
> @@ -1,8 +1,6 @@
> #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 */
> Index: linux-2.6/arch/mips/include/asm/fcntl.h
> ===================================================================
> --- linux-2.6.orig/arch/mips/include/asm/fcntl.h 2009-09-15 00:46:33.002006368 -0300
> +++ linux-2.6/arch/mips/include/asm/fcntl.h 2009-09-15 09:41:27.354254050 -0300
> @@ -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
> Index: linux-2.6/arch/mips/kernel/kspd.c
> ===================================================================
> --- linux-2.6.orig/arch/mips/kernel/kspd.c 2009-09-15 00:46:33.021004807 -0300
> +++ linux-2.6/arch/mips/kernel/kspd.c 2009-09-15 09:41:27.357254082 -0300
> @@ -82,6 +82,7 @@ static int sp_stopping = 0;
> #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
> Index: linux-2.6/arch/mips/lemote/lm2e/mem.c
> ===================================================================
> --- linux-2.6.orig/arch/mips/lemote/lm2e/mem.c 2009-09-15 00:46:33.054254081 -0300
> +++ linux-2.6/arch/mips/lemote/lm2e/mem.c 2009-09-15 09:41:27.357254082 -0300
> @@ -11,7 +11,7 @@
> /* 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;
>
> /*
> Index: linux-2.6/arch/mips/mm/cache.c
> ===================================================================
> --- linux-2.6.orig/arch/mips/mm/cache.c 2009-09-15 00:46:33.074254183 -0300
> +++ linux-2.6/arch/mips/mm/cache.c 2009-09-15 09:41:27.360254044 -0300
> @@ -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);
> Index: linux-2.6/arch/parisc/include/asm/fcntl.h
> ===================================================================
> --- linux-2.6.orig/arch/parisc/include/asm/fcntl.h 2009-09-15 00:46:33.082254364 -0300
> +++ linux-2.6/arch/parisc/include/asm/fcntl.h 2009-09-15 09:41:27.363254007 -0300
> @@ -1,14 +1,13 @@
> #ifndef _PARISC_FCNTL_H
> #define _PARISC_FCNTL_H
>
> -/* open/fcntl - O_SYNC is only implemented on blocks devices and on files
> - located on an ext2 file system */
> #define O_APPEND 000000010
> #define O_BLKSEEK 000000100 /* HPUX only */
> #define O_CREAT 000000400 /* not fcntl */
> #define O_EXCL 000002000 /* not fcntl */
> #define O_LARGEFILE 000004000
> -#define O_SYNC 000100000
> +#define __O_SYNC 000100000
> +#define O_SYNC (__O_SYNC|O_DSYNC)
> #define O_NONBLOCK 000200004 /* HPUX has separate NDELAY & NONBLOCK */
> #define O_NOCTTY 000400000 /* not fcntl */
> #define O_DSYNC 001000000 /* HPUX only */
> Index: linux-2.6/arch/sparc/include/asm/fcntl.h
> ===================================================================
> --- linux-2.6.orig/arch/sparc/include/asm/fcntl.h 2009-09-15 00:46:33.090254335 -0300
> +++ linux-2.6/arch/sparc/include/asm/fcntl.h 2009-09-15 09:41:27.367253956 -0300
> @@ -1,14 +1,12 @@
> #ifndef _SPARC_FCNTL_H
> #define _SPARC_FCNTL_H
>
> -/* open/fcntl - O_SYNC is only implemented on blocks devices and on files
> - located on an ext2 file system */
> #define O_APPEND 0x0008
> #define FASYNC 0x0040 /* fcntl, for BSD compatibility */
> #define O_CREAT 0x0200 /* not fcntl */
> #define O_TRUNC 0x0400 /* not fcntl */
> #define O_EXCL 0x0800 /* not fcntl */
> -#define O_SYNC 0x2000
> +#define O_DSYNC 0x2000 /* used to be O_SYNC, see below */
> #define O_NONBLOCK 0x4000
> #if defined(__sparc__) && defined(__arch64__)
> #define O_NDELAY 0x0004
> @@ -20,6 +18,21 @@
> #define O_DIRECT 0x100000 /* direct disk access hint */
> #define O_NOATIME 0x200000
> #define O_CLOEXEC 0x400000
> +/*
> + * 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 0x800000
> +#define O_SYNC (__O_SYNC|O_DSYNC)
>
> #define F_GETOWN 5 /* for sockets. */
> #define F_SETOWN 6 /* for sockets. */
> Index: linux-2.6/fs/sync.c
> ===================================================================
> --- linux-2.6.orig/fs/sync.c 2009-09-15 00:46:33.205253612 -0300
> +++ linux-2.6/fs/sync.c 2009-09-15 09:41:27.370254058 -0300
> @@ -287,10 +287,11 @@ SYSCALL_DEFINE1(fdatasync, unsigned int,
> */
> int generic_write_sync(struct file *file, loff_t pos, loff_t count)
> {
> - if (!(file->f_flags & O_SYNC) && !IS_SYNC(file->f_mapping->host))
> + if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
> return 0;
> return vfs_fsync_range(file, file->f_path.dentry, pos,
> - pos + count - 1, 1);
> + pos + count - 1,
> + (file->f_flags & __O_SYNC) ? 0 : 1);
> }
> EXPORT_SYMBOL(generic_write_sync);
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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