From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
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@xxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
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 0d34f5b5a6b0..4574121f4746 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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)
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 */
--
2.12.0
