Patch "CIFS: Fix splice read for non-cached files" has been added to the 4.10-stable tree

This is a note to let you know that I've just added the patch titled

CIFS: Fix splice read for non-cached files

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cifs-fix-splice-read-for-non-cached-files.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Pavel Shilovsky <[email protected]>
Date: Thu, 19 Jan 2017 13:53:15 -0800
Subject: CIFS: Fix splice read for non-cached files

From: Pavel Shilovsky <[email protected]>

commit 9c25702cee1405099f982894c865c163de7909a8 upstream.

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.

---
 fs/cifs/file.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

@@ -2884,7 +2884,15 @@ cifs_readdata_to_iov(struct cifs_readdat
 	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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/cifs-fix-splice-read-for-non-cached-files.patch