From 398a4738033b0842dd7e56fc263ad9f51994dc3d Mon Sep 17 00:00:00 2001

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Date: Tue, 20 Jun 2017 07:05:43 -0500

Subject: [PATCH 04/11] fs: Introduce RWF_NOWAIT and FMODE_AIO_NOWAIT

Git-commit: b745fafaf70c0a98a2e1e7ac8cb14542889ceb0e

Patch-mainline: v4.13-rc1

References: FATE#321994

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.

FMODE_AIO_NOWAIT is a flag which identifies the file opened is capable

of returning -EAGAIN if the AIO call will block. This must be set by

supporting filesystems in the ->open() call.

Filesystems xfs, btrfs and ext4 would be supported in the following patches.

Reviewed-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Jan Kara <jack@suse.cz>

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

 fs/aio.c                | 6 ++++++

 include/linux/fs.h      | 9 +++++++++

 include/uapi/linux/fs.h | 4 +++-

 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/fs/aio.c b/fs/aio.c

index 020fa0045e3c..34027b67e2f4 100644

--- a/fs/aio.c

+++ b/fs/aio.c

@@ -1592,6 +1592,12 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,

 		goto out_put_req;

 	}

+	if ((req->common.ki_flags & IOCB_NOWAIT) &&

+			!(req->common.ki_flags & IOCB_DIRECT)) {

+		ret = -EOPNOTSUPP;

+		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/include/linux/fs.h b/include/linux/fs.h

index 8b159244d696..c5b445456639 100644

--- a/include/linux/fs.h

+++ b/include/linux/fs.h

@@ -142,6 +142,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,

 /* File was opened by fanotify and shouldn't generate fanotify events */

 #define FMODE_NONOTIFY		((__force fmode_t)0x4000000)

+/* File is capable of returning -EAGAIN if AIO will block */

+#define FMODE_AIO_NOWAIT	((__force fmode_t)0x8000000)

+

 /*

  * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector

  * that indicates that they should check the contents of the iovec are

@@ -268,6 +271,7 @@ 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;

@@ -3078,6 +3082,11 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags)

 	if (unlikely(flags & ~RWF_SUPPORTED))

 		return -EOPNOTSUPP;

+	if (flags & RWF_NOWAIT) {

+		if (!(ki->ki_filp->f_mode & FMODE_AIO_NOWAIT))

+			return -EOPNOTSUPP;

+		ki->ki_flags |= IOCB_NOWAIT;

+	}

 	if (flags & RWF_HIPRI)

 		ki->ki_flags |= IOCB_HIPRI;

 	if (flags & RWF_DSYNC)

diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h

index 937c3e39650a..27d8c36c04af 100644

--- a/include/uapi/linux/fs.h

+++ b/include/uapi/linux/fs.h

@@ -360,7 +360,9 @@ 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 */

-#define RWF_SUPPORTED			(RWF_HIPRI | RWF_DSYNC | RWF_SYNC)

+#define RWF_SUPPORTED			(RWF_HIPRI | RWF_DSYNC | RWF_SYNC |\

+					 RWF_NOWAIT)

 #endif /* _UAPI_LINUX_FS_H */

-- 

2.12.3