Commit 6fcc5420 authored Jul 20, 2014 by Boaz Harrosh Committed by Christoph Hellwig Jul 24, 2014

direct-io: fix uninitialized warning in do_direct_IO()



The following warnings:

  fs/direct-io.c: In function ‘__blockdev_direct_IO’:
  fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  fs/direct-io.c:913:16: note: ‘to’ was declared here
  fs/direct-io.c:1011:12: warning: ‘from’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  fs/direct-io.c:913:10: note: ‘from’ was declared here

are false positive because dio_get_page() either fails, or sets both
'from' and 'to'.

Paul Bolle said ...
Maybe it's better to move initializing "to" and "from" out of
dio_get_page(). That _might_ make it easier for both the the reader and
the compiler to understand what's going on. Something like this:

Christoph Hellwig said ...
The fix of moving the code definitively looks nicer, while I think
uninitialized_var is horrible wart that won't get anywhere near my code.

Boaz Harrosh: I agree with Christoph and Paul

Signed-off-by: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

parent 82e13c71

fs/direct-io.c

+7 −7

Original line number	Diff line number	Diff line
		@@ -198,9 +198,8 @@ static inline int dio_refill_pages(struct dio dio, struct dio_submit sdio)
		* L1 cache.
		*/
		static inline struct page dio_get_page(struct dio dio,
		struct dio_submit sdio, size_t from, size_t *to)
		struct dio_submit *sdio)
		{
		int n;
		if (dio_pages_present(sdio) == 0) {
		int ret;

		@@ -209,10 +208,7 @@ static inline struct page dio_get_page(struct dio dio,
		return ERR_PTR(ret);
		BUG_ON(dio_pages_present(sdio) == 0);
		}
		n = sdio->head++;
		*from = n ? 0 : sdio->from;
		*to = (n == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
		return dio->pages[n];
		return dio->pages[sdio->head];
		}

		/**
		@@ -911,11 +907,15 @@ static int do_direct_IO(struct dio dio, struct dio_submit sdio,
		while (sdio->block_in_file < sdio->final_block_in_request) {
		struct page *page;
		size_t from, to;
		page = dio_get_page(dio, sdio, &from, &to);

		page = dio_get_page(dio, sdio);
		if (IS_ERR(page)) {
		ret = PTR_ERR(page);
		goto out;
		}
		from = sdio->head ? 0 : sdio->from;
		to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
		sdio->head++;

		while (from < to) {
		unsigned this_chunk_bytes; /* # of bytes mapped */