With the new read/write with flags syscalls we can support a flag
to enable O_DSYNC semantics on a per-operation basis. This іs
useful to implement protocols like SMB, NFS or SCSI that have such
per-operation flags.
Example program below:
cat > pwritev2.c << EOF
(off_t) val, \
(off_t) ((((uint64_t) (val)) >> (sizeof (long) * 4)) >> (sizeof (long) * 4))
static ssize_t
pwritev2(int fd, const struct iovec *iov, int iovcnt, off_t offset, int flags)
{
return syscall(__NR_pwritev2, fd, iov, iovcnt, LO_HI_LONG(offset),
flags);
}
int main(int argc, char **argv)
{
int fd = open(argv[1], O_WRONLY|O_CREAT|O_TRUNC, 0666);
char buf[1024];
struct iovec iov = { .iov_base = buf, .iov_len = 1024 };
int ret;
if (fd < 0) {
perror("open");
return 0;
}
memset(buf, 0xfe, sizeof(buf));
ret = pwritev2(fd, &iov, 1, 0, RWF_DSYNC);
if (ret < 0)
perror("pwritev2");
else
printf("ret = %d\n", ret);
return 0;
}
EOF
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/ceph/file.c | 4 +++-
fs/fuse/file.c | 2 ++
fs/nfs/file.c | 10 ++++++----
fs/ocfs2/file.c | 6 ++++--
fs/read_write.c | 11 ++++++++---
include/linux/fs.h | 3 ++-
mm/filemap.c | 4 +++-
7 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 2eb02f8..e59f1f1 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -968,7 +968,9 @@ retry_snap:
ceph_put_cap_refs(ci, got);
if (written >= 0 &&
- ((file->f_flags & O_SYNC) || IS_SYNC(file->f_mapping->host) ||
+ ((file->f_flags & O_SYNC) ||
+ IS_SYNC(file->f_mapping->host) ||
+ (iocb->ki_rwflags & RWF_DSYNC) ||
ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL))) {
err = vfs_fsync_range(file, pos, pos + written - 1, 1);
if (err < 0)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index caa8d95..bb4fb23 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1248,6 +1248,8 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
written += written_buffered;
iocb->ki_pos = pos + written_buffered;
} else {
+ if (iocb->ki_rwflags & RWF_DSYNC)
+ return -EINVAL;
written = fuse_perform_write(file, mapping, from, pos);
if (written >= 0)
iocb->ki_pos = pos + written;
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 524dd80..a9e6cc4 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -621,13 +621,15 @@ static const struct vm_operations_struct nfs_file_vm_ops = {
.remap_pages = generic_file_remap_pages,
};
-static int nfs_need_sync_write(struct file *filp, struct inode *inode)
+static int nfs_need_sync_write(struct kiocb *iocb, struct inode *inode)
{
struct nfs_open_context *ctx;
- if (IS_SYNC(inode) || (filp->f_flags & O_DSYNC))
+ if (IS_SYNC(inode) ||
+ (iocb->ki_filp->f_flags & O_DSYNC) ||
+ (iocb->ki_rwflags & RWF_DSYNC))
return 1;
- ctx = nfs_file_open_context(filp);
+ ctx = nfs_file_open_context(iocb->ki_filp);
if (test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags) ||
nfs_ctx_key_to_expire(ctx))
return 1;
@@ -674,7 +676,7 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
written = result;
/* Return error values for O_DSYNC and IS_SYNC() */
- if (result >= 0 && nfs_need_sync_write(file, inode)) {
+ if (result >= 0 && nfs_need_sync_write(iocb, inode)) {
int err = vfs_fsync(file, 0);
if (err < 0)
result = err;
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index d96f60d..8f29714 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2375,8 +2375,10 @@ 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_DSYNC) && !direct_io) || IS_SYNC(inode) ||
- ((file->f_flags & O_DIRECT) && !direct_io)) {
+ if (((file->f_flags & O_DSYNC) && !direct_io) ||
+ IS_SYNC(inode) ||
+ ((file->f_flags & O_DIRECT) && !direct_io) ||
+ (iocb->ki_rwflags & RWF_DSYNC)) {
ret = filemap_fdatawrite_range(file->f_mapping, *ppos,
*ppos + count - 1);
if (ret < 0)
diff --git a/fs/read_write.c b/fs/read_write.c
index 5592a18..8af8925 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -837,8 +837,13 @@ static ssize_t do_readv_writev(int type, struct file *file,
ret = do_iter_readv_writev(file, type, iov, nr_segs, tot_len,
pos, iter_fn, flags);
} else {
- if (type == READ && (flags & RWF_NONBLOCK))
- return -EAGAIN;
+ if (type == READ) {
+ if (flags & RWF_NONBLOCK)
+ return -EAGAIN;
+ } else {
+ if (flags & RWF_DSYNC)
+ return -EINVAL;
+ }
if (fnv)
ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
@@ -886,7 +891,7 @@ ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,
return -EBADF;
if (!(file->f_mode & FMODE_CAN_WRITE))
return -EINVAL;
- if (flags & ~0)
+ if (flags & ~RWF_DSYNC)
return -EINVAL;
return do_readv_writev(WRITE, file, vec, vlen, pos, flags);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index cf759fa..005e7c8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1478,7 +1478,8 @@ struct block_device_operations;
#define HAVE_UNLOCKED_IOCTL 1
/* These flags are used for the readv/writev syscalls with flags. */
-#define RWF_NONBLOCK 0x00000001
+#define RWF_NONBLOCK 0x00000001
+#define RWF_DSYNC 0x00000002
struct iov_iter;
diff --git a/mm/filemap.c b/mm/filemap.c
index f9ffb6f..40831ae 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2659,7 +2659,9 @@ int generic_write_sync(struct kiocb *iocb, loff_t count)
struct file *file = iocb->ki_filp;
if (count > 0 &&
- ((file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host))) {
+ ((file->f_flags & O_DSYNC) ||
+ (iocb->ki_rwflags & RWF_DSYNC) ||
+ IS_SYNC(file->f_mapping->host))) {
bool fdatasync = !(file->f_flags & __O_SYNC);
ssize_t ret = 0;
--
1.9.1
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