Commit 9c25702c authored Jan 19, 2017 by Pavel Shilovsky Committed by Steve French Feb 01, 2017

CIFS: Fix splice read for non-cached files

Currently we call copy_page_to_iter() for uncached reading into a pipe.
This is wrong because it treats pages as VFS cache pages and copies references
rather than actual data. When we are trying to read from the pipe we end up
calling page_cache_pipe_buf_confirm() which returns -ENODATA. This error
is translated into 0 which is returned to a user.

This issue is reproduced by running xfs-tests suite (generic test #249)
against mount points with "cache=none". Fix it by mapping pages manually
and calling copy_to_iter() that copies data into the pipe.

Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>

parent b9be76d5

fs/cifs/file.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -2884,7 +2884,15 @@ cifs_readdata_to_iov(struct cifs_readdata rdata, struct iov_iter iter)
		for (i = 0; i < rdata->nr_pages; i++) {
		struct page *page = rdata->pages[i];
		size_t copy = min_t(size_t, remaining, PAGE_SIZE);
		size_t written = copy_page_to_iter(page, 0, copy, iter);
		size_t written;

		if (unlikely(iter->type & ITER_PIPE)) {
		void *addr = kmap_atomic(page);

		written = copy_to_iter(addr, copy, iter);
		kunmap_atomic(addr);
		} else
		written = copy_page_to_iter(page, 0, copy, iter);
		remaining -= written;
		if (written < copy && iov_iter_count(iter) > 0)
		break;

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