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Date: Fri, 14 Apr 2017 07:02:51 -0500
From: Goldwyn Rodrigues <rgoldwyn@...e.de>
To: linux-fsdevel@...r.kernel.org
Cc: 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, sagi@...mberg.me, avi@...lladb.com,
axboe@...nel.dk, linux-api@...r.kernel.org, willy@...radead.org,
tom.leiming@...il.com, Goldwyn Rodrigues <rgoldwyn@...e.com>
Subject: [PATCH 2/8] nowait aio: Introduce RWF_NOWAIT
From: Goldwyn Rodrigues <rgoldwyn@...e.com>
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.
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>
---
fs/9p/vfs_file.c | 3 +++
fs/aio.c | 9 +++++++--
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 +++
fs/read_write.c | 2 +-
include/linux/fs.h | 3 +++
include/uapi/linux/fs.h | 1 +
mm/filemap.c | 3 +++
11 files changed, 33 insertions(+), 3 deletions(-)
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 b8a33f5beef5..d3b5c8dc6549 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1546,12 +1546,12 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
return -EINVAL;
}
- if (unlikely(iocb->aio_rw_flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC))) {
+ if (unlikely(iocb->aio_rw_flags &
+ ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_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) ||
@@ -1593,6 +1593,11 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
}
req->common.ki_flags |= iocb_rw_flags(iocb->aio_rw_flags);
+ if ((req->common.ki_flags & IOCB_NOWAIT) &&
+ !(req->common.ki_flags & IOCB_DIRECT)) {
+ ret = -EINVAL;
+ goto out_put_req;
+ }
ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
if (unlikely(ret)) {
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 26cc95421cca..af28419b1731 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1267,6 +1267,9 @@ 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 aa3debbba826..a828ab3e7775 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2638,6 +2638,9 @@ 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 ec238fb5a584..72786e798319 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 aab32fc3d6a8..ab419caebd5f 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -991,6 +991,9 @@ 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/fs/read_write.c b/fs/read_write.c
index 9aa557bb471c..97f3d6d444b8 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -678,7 +678,7 @@ static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
struct kiocb kiocb;
ssize_t ret;
- if (flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC))
+ if (flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT))
return -EOPNOTSUPP;
init_sync_kiocb(&kiocb, filp);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 35cfb08ceb9d..e44de1c981a0 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;
@@ -3058,6 +3059,8 @@ static inline int iocb_rw_flags(int flags)
res |= IOCB_DSYNC;
if (flags & RWF_SYNC)
res |= (IOCB_DSYNC | IOCB_SYNC);
+ if (flags & RWF_NOWAIT)
+ res |= IOCB_NOWAIT;
return res;
}
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 048a85e9f017..7bcaef101876 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -347,5 +347,6 @@ struct fscrypt_policy {
#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 1694623a6289..d51670b7fe6b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2982,6 +2982,9 @@ 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
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