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Date: Thu, 25 May 2017 10:30:18 +0200
From: Jan Kara <jack@...e.cz>
To: Goldwyn Rodrigues <rgoldwyn@...e.de>
Cc: linux-fsdevel@...r.kernel.org, jack@...e.com, hch@...radead.org,
linux-block@...r.kernel.org, linux-btrfs@...r.kernel.org,
linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
axboe@...nel.dk, linux-api@...r.kernel.org,
adam.manzanares@....com, viro@...iv.linux.org.uk,
Goldwyn Rodrigues <rgoldwyn@...e.com>
Subject: Re: [PATCH 04/10] fs: Introduce RWF_NOWAIT
On Wed 24-05-17 11:41:44, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@...e.com>
>
> RWF_NOWAIT informs kernel to bail out if an AIO request will block
> for reasons such as file allocations, or a writeback triggered,
> or would block while allocating requests while performing
> direct I/O.
>
> RWF_NOWAIT is translated to IOCB_NOWAIT for iocb->ki_flags.
>
> The check for -EOPNOTSUPP is placed in generic_file_write_iter(). This
> is called by most filesystems, either through fsops.write_iter() or through
> the function defined by write_iter(). If not, we perform the check defined
> by .write_iter() which is called for direct IO specifically.
>
> Filesystems xfs, btrfs and ext4 would be supported in the following patches.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@...e.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
Looks good now. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/9p/vfs_file.c | 3 +++
> fs/aio.c | 13 +++++++++++++
> fs/ceph/file.c | 3 +++
> fs/cifs/file.c | 3 +++
> fs/fuse/file.c | 3 +++
> fs/nfs/direct.c | 3 +++
> fs/ocfs2/file.c | 3 +++
> include/linux/fs.h | 5 ++++-
> include/uapi/linux/fs.h | 1 +
> mm/filemap.c | 3 +++
> 10 files changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 3de3b4a89d89..403681db7723 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -411,6 +411,9 @@ v9fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> loff_t origin;
> int err = 0;
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> retval = generic_write_checks(iocb, from);
> if (retval <= 0)
> return retval;
> diff --git a/fs/aio.c b/fs/aio.c
> index 020fa0045e3c..9616dc733103 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1592,6 +1592,19 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
> goto out_put_req;
> }
>
> + if (req->common.ki_flags & IOCB_NOWAIT) {
> + if (!(req->common.ki_flags & IOCB_DIRECT)) {
> + ret = -EOPNOTSUPP;
> + goto out_put_req;
> + }
> +
> + if ((iocb->aio_lio_opcode != IOCB_CMD_PWRITE) &&
> + (iocb->aio_lio_opcode != IOCB_CMD_PWRITEV)) {
> + ret = -EINVAL;
> + goto out_put_req;
> + }
> + }
> +
> ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
> if (unlikely(ret)) {
> pr_debug("EFAULT: aio_key\n");
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 3fdde0b283c9..a53fd2675b1b 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1300,6 +1300,9 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
> int err, want, got;
> loff_t pos;
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> if (ceph_snap(inode) != CEPH_NOSNAP)
> return -EROFS;
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 0fd081bd2a2f..ff84fa9ddb6c 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2725,6 +2725,9 @@ ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
> * write request.
> */
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> rc = generic_write_checks(iocb, from);
> if (rc <= 0)
> return rc;
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 3ee4fdc3da9e..812c7bd0c290 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1425,6 +1425,9 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
> struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(file);
> ssize_t res;
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> if (is_bad_inode(inode))
> return -EIO;
>
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index 6fb9fad2d1e6..c8e7dd76126c 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c
> @@ -979,6 +979,9 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
> dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
> file, iov_iter_count(iter), (long long) iocb->ki_pos);
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> result = generic_write_checks(iocb, iter);
> if (result <= 0)
> return result;
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index bfeb647459d9..e7f8ba890305 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -2235,6 +2235,9 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
> if (count == 0)
> return 0;
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> direct_io = iocb->ki_flags & IOCB_DIRECT ? 1 : 0;
>
> inode_lock(inode);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index dc0ab585cd56..2a7d14af6d12 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -268,6 +268,7 @@ struct writeback_control;
> #define IOCB_DSYNC (1 << 4)
> #define IOCB_SYNC (1 << 5)
> #define IOCB_WRITE (1 << 6)
> +#define IOCB_NOWAIT (1 << 7)
>
> struct kiocb {
> struct file *ki_filp;
> @@ -3060,7 +3061,7 @@ static inline int iocb_flags(struct file *file)
>
> static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags)
> {
> - if (unlikely(flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC)))
> + if (unlikely(flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT)))
> return -EOPNOTSUPP;
>
> if (flags & RWF_HIPRI)
> @@ -3069,6 +3070,8 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags)
> ki->ki_flags |= IOCB_DSYNC;
> if (flags & RWF_SYNC)
> ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
> + if (flags & RWF_NOWAIT)
> + ki->ki_flags |= IOCB_NOWAIT;
> return 0;
> }
>
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 24e61a54feaa..29969fb7f9a7 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -360,5 +360,6 @@ struct fscrypt_key {
> #define RWF_HIPRI 0x00000001 /* high priority request, poll if possible */
> #define RWF_DSYNC 0x00000002 /* per-IO O_DSYNC */
> #define RWF_SYNC 0x00000004 /* per-IO O_SYNC */
> +#define RWF_NOWAIT 0x00000008 /* per-IO, return -EAGAIN if operation would block */
>
> #endif /* _UAPI_LINUX_FS_H */
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 87aba7698584..097213275461 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3006,6 +3006,9 @@ ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> struct inode *inode = file->f_mapping->host;
> ssize_t ret;
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> inode_lock(inode);
> ret = generic_write_checks(iocb, from);
> if (ret > 0)
> --
> 2.12.0
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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