| Message ID | 20170606111939.27272-5-rgoldwyn@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Jun 06, 2017 at 06:19:33AM -0500, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues <rgoldwyn@suse.com> > > 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. > > 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. Umm... What about ->write_iter() instances outside of fs/*? Even in fs/*, consider e.g. int cifs_get_writer(struct cifsInodeInfo *cinode) { int rc; start: rc = wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK, TASK_KILLABLE); and cifs_file_write_iter() calling it before going to generic_file_write_iter(). Ditto for cifs_struct_writev()... coda_file_write_iter() does inode_lock() before calling vfs_iter_write(). ext2_dax_write_iter(): inode_lock(). f2fs_file_write_iter(): ditto. fuse_file_write_iter(): ditto in case when ->writeback_cache is false. gfs2 is O_APPEND case: almost certainly blocks. ncp_file_write_iter(): blocks (mutex_lock(&NCP_FINFO(inode)->open_mutex) in ncp_make_open(), not to mention anything else). ntfs_file_write_iter(): inode_lock(). orangefs_file_write_iter(): ditto. ubifs_write_iter(): may block in update_mctime(). udf_file_write_iter(): inode_lock(). Lustre sure as hell does block before it gets anywhere near mm/filemap.c. And that - just from looking at regular files. Then we have sockets and pipes, not to mention weird stuff like fs/fuse/cuse.c, etc. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 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/fs/ceph/file.c b/fs/ceph/file.c index 29308a80d66f..366b0bb71f97 100644 --- a/fs/ceph/file.c +++ b/fs/ceph/file.c @@ -1300,6 +1300,9 @@ 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 0fd081bd2a2f..ff84fa9ddb6c 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -2725,6 +2725,9 @@ 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 3ee4fdc3da9e..812c7bd0c290 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 6fb9fad2d1e6..c8e7dd76126c 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -979,6 +979,9 @@ 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/include/linux/fs.h b/include/linux/fs.h index dc0ab585cd56..2a7d14af6d12 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -268,6 +268,7 @@ 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; @@ -3060,7 +3061,7 @@ static inline int iocb_flags(struct file *file) static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags) { - if (unlikely(flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC))) + if (unlikely(flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT))) return -EOPNOTSUPP; if (flags & RWF_HIPRI) @@ -3069,6 +3070,8 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags) ki->ki_flags |= IOCB_DSYNC; if (flags & RWF_SYNC) ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC); + if (flags & RWF_NOWAIT) + ki->ki_flags |= IOCB_NOWAIT; return 0; } diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 24e61a54feaa..29969fb7f9a7 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -360,5 +360,6 @@ 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 */ #endif /* _UAPI_LINUX_FS_H */ diff --git a/mm/filemap.c b/mm/filemap.c index 87aba7698584..097213275461 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3006,6 +3006,9 @@ 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)