From mboxrd@z Thu Jan 1 00:00:00 1970 From: Goldwyn Rodrigues Subject: [PATCH 1/8] nowait aio: Introduce IOCB_RW_FLAG_NOWAIT Date: Mon, 3 Apr 2017 13:53:00 -0500 Message-ID: <20170403185307.6243-2-rgoldwyn@suse.de> References: <20170403185307.6243-1-rgoldwyn@suse.de> Return-path: In-Reply-To: <20170403185307.6243-1-rgoldwyn-l3A5Bk7waGM@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: jack-IBi9RG/b67k@public.gmane.org, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org, avi-VrcmuVmyx1hWk0Htik3J/w@public.gmane.org, axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, tom.leiming-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Goldwyn Rodrigues List-Id: linux-api@vger.kernel.org From: Goldwyn Rodrigues This flag 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. Unfortunately, aio_flags is not checked for validity, which would break existing applications which have it set to anything besides zero or IOCB_FLAG_RESFD. So, we are using aio_reserved1 and renaming it to aio_rw_flags. IOCB_RW_FLAG_NOWAIT is translated to IOCB_NOWAIT for iocb->ki_flags. Added FS_NOWAIT to make sure VFS knows that the filesystem is capable of performing direct-AIO with IOCB_RW_FLAG_NOWAIT. --- fs/aio.c | 15 ++++++++++++++- include/linux/fs.h | 2 ++ include/uapi/linux/aio_abi.h | 9 ++++++++- 3 files changed, 24 insertions(+), 2 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index f52d925..25ae59b 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1541,11 +1541,16 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, ssize_t ret; /* enforce forwards compatibility on users */ - if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) { + if (unlikely(iocb->aio_reserved2)) { pr_debug("EINVAL: reserve field set\n"); return -EINVAL; } + if (unlikely(iocb->aio_rw_flags & ~IOCB_RW_FLAG_NOWAIT)) { + pr_debug("EINVAL: aio_rw_flags set with incompatible flags\n"); + return -EINVAL; + } + /* prevent overflows */ if (unlikely( (iocb->aio_buf != (unsigned long)iocb->aio_buf) || @@ -1586,6 +1591,14 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, req->common.ki_flags |= IOCB_EVENTFD; } + if (iocb->aio_rw_flags & IOCB_RW_FLAG_NOWAIT) { + if (!(file->f_inode->i_sb->s_type->fs_flags & FS_NOWAIT)) { + ret = -EOPNOTSUPP; + goto out_put_req; + } + req->common.ki_flags |= IOCB_NOWAIT; + } + 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 7251f7b..802cfe2 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -270,6 +270,7 @@ 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; @@ -2020,6 +2021,7 @@ struct file_system_type { #define FS_HAS_SUBTYPE 4 #define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */ #define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */ +#define FS_NOWAIT 65536 /* FS supports nowait direct AIO */ struct dentry *(*mount) (struct file_system_type *, int, const char *, void *); void (*kill_sb) (struct super_block *); diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h index bb2554f..6d98cbe 100644 --- a/include/uapi/linux/aio_abi.h +++ b/include/uapi/linux/aio_abi.h @@ -54,6 +54,13 @@ enum { */ #define IOCB_FLAG_RESFD (1 << 0) +/* + * Flags for aio_rw_flags member of "struct iocb". + * IOCB_RW_FLAG_NOWAIT - Set if the user wants the iocb to fail if it + * would block for operations such as disk allocation. + */ +#define IOCB_RW_FLAG_NOWAIT (1 << 1) + /* read() from /dev/aio returns these structures. */ struct io_event { __u64 data; /* the data field from the iocb */ @@ -79,7 +86,7 @@ struct io_event { struct iocb { /* these are internal to the kernel/libc. */ __u64 aio_data; /* data to be returned in event's data */ - __u32 PADDED(aio_key, aio_reserved1); + __u32 PADDED(aio_key, aio_rw_flags); /* the kernel sets aio_key to the req # */ /* common fields */ -- 2.10.2