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fix ITER_PIPE interaction with direct_IO 

by making sure we call iov_iter_advance() on original
iov_iter even if direct_IO (done on its copy) has returned 0.
It's a no-op for old iov_iter flavours and does the right thing
(== truncation of the stuff we'd allocated, but not filled) in
ITER_PIPE case.  Failures (e.g. -EIO) get caught and dealt with
by cleanup in generic_file_read_iter().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-10-10 13:26:27 -04:00
parent a949e63992
commit c3a6902404
3 changed files with 5 additions and 11 deletions
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12
fs/splice.c
View File

@ -315,15 +315,9 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
*ppos = kiocb.ki_pos;
file_accessed(in);
} else if (ret < 0) {
if (WARN_ON(to.idx != idx || to.iov_offset)) {
/*
* a bogus ->read_iter() has copied something and still
* returned an error instead of a short read.
*/
to.idx = idx;
to.iov_offset = 0;
iov_iter_advance(&to, 0); /* to free what was emitted */
}
to.idx = idx;
to.iov_offset = 0;
iov_iter_advance(&to, 0); /* to free what was emitted */
/*
* callers of ->splice_read() expect -EAGAIN on
* "can't put anything in there", rather than -EFAULT.

2
fs/xfs/xfs_file.c
View File

@ -317,7 +317,7 @@ xfs_file_dio_aio_read(
data = *to;
ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
xfs_get_blocks_direct, NULL, NULL, 0);
if (ret > 0) {
if (ret >= 0) {
iocb->ki_pos += ret;
iov_iter_advance(to, ret);
}

2
mm/filemap.c
View File

@ -1920,7 +1920,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
retval = mapping->a_ops->direct_IO(iocb, &data);
}
if (retval > 0) {
if (retval >= 0) {
iocb->ki_pos += retval;
iov_iter_advance(iter, retval);
}