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fs: support RWF_NOWAIT for buffered reads

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This is based on the old idea and code from Milosz Tanski.  With the aio
nowait code it becomes mostly trivial now.  Buffered writes continue to
return -EOPNOTSUPP if RWF_NOWAIT is passed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig
2017-08-29 16:13:20 +02:00
committed by Al Viro
parent 3239d83484
commit 91f9943e1c
5 changed files with 20 additions and 15 deletions
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6
fs/btrfs/file.c
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@@ -1886,6 +1886,10 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
loff_t oldsize;
int clean_page = 0;
if (!(iocb->ki_flags & IOCB_DIRECT) &&
(iocb->ki_flags & IOCB_NOWAIT))
return -EOPNOTSUPP;
if (!inode_trylock(inode)) {
if (iocb->ki_flags & IOCB_NOWAIT)
return -EAGAIN;
@@ -3105,7 +3109,7 @@ out:
static int btrfs_file_open(struct inode *inode, struct file *filp)
{
filp->f_mode |= FMODE_AIO_NOWAIT;
filp->f_mode |= FMODE_NOWAIT;
return generic_file_open(inode, filp);
}