Re: [PATCH v5 7/7] fs: add a flag for per-operation O_DSYNC semantics

From: Sage Weil
Date: Mon Nov 10 2014 - 11:08:06 EST

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On Wed, 5 Nov 2014, Milosz Tanski wrote:
> From: Christoph Hellwig <hch@xxxxxx>
>
> With the new read/write with flags syscalls we can support a flag
> to enable O_DSYNC semantics on a per-operation basis. This ?s
> 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>
> [milosz@xxxxxxxxx: added flag check to compat_do_readv_writev()]
> Signed-off-by: Milosz Tanski <milosz@xxxxxxxxx>

Ceph bits

Acked-by: Sage Weil <sage@xxxxxxxxxx>

> ---
> fs/ceph/file.c | 4 +++-
> fs/fuse/file.c | 2 ++
> fs/nfs/file.c | 10 ++++++----
> fs/ocfs2/file.c | 6 ++++--
> fs/read_write.c | 20 +++++++++++++++-----
> include/linux/fs.h | 3 ++-
> mm/filemap.c | 4 +++-
> 7 files changed, 35 insertions(+), 14 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index b798b5c..2d4e15a 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -983,7 +983,9 @@ 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 aa9046f..c59b0b7 100644
> --- a/fs/nfs/file.c
> +++ b/fs/nfs/file.c
> @@ -652,13 +652,15 @@ 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;
> @@ -705,7 +707,7 @@ 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 bb66ca4..8f9a86b 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -2374,8 +2374,10 @@ 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 cba7d4c..3443265 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -839,8 +839,13 @@ 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,
> @@ -888,7 +893,7 @@ 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);
> @@ -1080,8 +1085,13 @@ static ssize_t compat_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,
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 7d0e116..7786b88 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1460,7 +1460,8 @@ 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 6107058..4fbef99 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2669,7 +2669,9 @@ 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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