Commit 6b2f3d1f authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jan Kara
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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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: default avatarKyle McMartin <kyle@mcmartin.ca>
Acked-by: default avatarUlrich Drepper <drepper@redhat.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 59bc0552
#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
......
......@@ -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 */
......
......@@ -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
......
......@@ -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
......
......@@ -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) ||
......
......@@ -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);
......
#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 */
......
#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. */
......
......@@ -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
/*
......
......@@ -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
......
......@@ -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);
}
}
......
......@@ -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;
}
......
......@@ -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);
......
......@@ -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;
......
......@@ -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)
......
......@@ -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);
......
......@@ -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)
......
......@@ -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;
}
......
......@@ -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)
......
......@@ -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);
......
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