Commit b745fafa authored by Goldwyn Rodrigues's avatar Goldwyn Rodrigues Committed by Jens Axboe
Browse files

fs: Introduce RWF_NOWAIT and FMODE_AIO_NOWAIT 



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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9830f4be

fs/aio.c

+6 −0
Original line number Diff line number Diff line
@@ -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");

include/linux/fs.h

+9 −0
Original line number Diff line number Diff line
@@ -143,6 +143,9 @@ 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
@@ -269,6 +272,7 @@ 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;
@@ -3064,6 +3068,11 @@ 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)

include/uapi/linux/fs.h

+3 −1
Original line number Diff line number Diff line
@@ -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 */

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