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CIFS: Fix splice read for non-cached files

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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.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Shilovsky 2017-01-19 13:53:15 -08:00 committed by Greg Kroah-Hartman
parent 24427cd71d
commit c06d74df4e
1 changed files with 9 additions and 1 deletions
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10
fs/cifs/file.c
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@ -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;