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vfs: Implement proper O_SYNC semantics

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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>
This commit is contained in:
Christoph Hellwig 2009-10-27 11:05:28 +01:00 committed by Jan Kara
parent 59bc055211
commit 6b2f3d1f76
24 changed files with 109 additions and 40 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

19
arch/alpha/include/asm/fcntl.h
View file

@ -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

2
arch/blackfin/include/asm/fcntl.h
View file

@ -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 */

17
arch/mips/include/asm/fcntl.h
View file

@ -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

1
arch/mips/kernel/kspd.c
View file

@ -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

2
arch/mips/loongson/common/mem.c
View file

@ -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) ||

2
arch/mips/mm/cache.c
View file

@ -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);

5
arch/parisc/include/asm/fcntl.h
View file

@ -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 */

19
arch/sparc/include/asm/fcntl.h
View file

@ -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. */

3
arch/x86/mm/pat.c
View file

@ -704,9 +704,8 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
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;
}
#ifdef CONFIG_X86_32
/*

6
drivers/char/mem.c
View file

@ -43,7 +43,7 @@ static inline int uncached_access(struct file *file, unsigned long addr)
{
#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)
@ -56,9 +56,9 @@ static inline int uncached_access(struct file *file, unsigned long addr)
#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

2
drivers/usb/gadget/file_storage.c
View file

@ -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);
}
}

5
fs/afs/write.c
View file

@ -692,8 +692,9 @@ ssize_t afs_file_write(struct kiocb *iocb, const struct iovec *iov,
}
/* 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;
}

4
fs/btrfs/file.c
View file

@ -909,7 +909,7 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
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,
@ -1076,7 +1076,7 @@ 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);

3
fs/cifs/dir.c
View file

@ -214,7 +214,8 @@ int cifs_posix_open(char *full_path, struct inode **pinode,
posix_flags |= SMB_O_EXCL;
if (oflags & O_TRUNC)
posix_flags |= SMB_O_TRUNC;
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;

6
fs/cifs/file.c
View file

@ -76,8 +76,10 @@ static inline fmode_t cifs_posix_convert_flags(unsigned int flags)
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)

9
fs/namei.c
View file

@ -1678,6 +1678,15 @@ struct file *do_filp_open(int dfd, const char *pathname,
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);

4
fs/nfs/file.c
View file

@ -581,7 +581,7 @@ static int nfs_need_sync_write(struct file *filp, struct inode *inode)
{
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))
@ -622,7 +622,7 @@ static ssize_t nfs_file_write(struct kiocb *iocb, const struct iovec *iov,
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)

2
fs/nfs/write.c
View file

@ -774,7 +774,7 @@ int nfs_updatepage(struct file *file, struct page *page,
*/
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;
}

2
fs/ocfs2/file.c
View file

@ -2006,7 +2006,7 @@ 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)

5
fs/sync.c
View file

@ -295,10 +295,11 @@ SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
*/
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);

2
fs/ubifs/file.c
View file

@ -1401,7 +1401,7 @@ static ssize_t ubifs_aio_write(struct kiocb *iocb, const struct iovec *iov,
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;

2
fs/xfs/linux-2.6/xfs_lrw.c
View file

@ -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)) {
loff_t end = pos + ret - 1;
int error2;

25
include/asm-generic/fcntl.h
View file

@ -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

2
sound/core/rawmidi.c
View file

@ -1257,7 +1257,7 @@ static ssize_t snd_rawmidi_write(struct file *file, const char __user *buf,
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;