Boaz,
On Thu, 2014-07-17 at 12:37 +0300, Boaz Harrosh wrote:
> From: Paul Bolle <pebolle@xxxxxxxxxx>
>
> 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'.
>
> 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 defintively 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: Paul Bolle <pebolle@xxxxxxxxxx>
This is simply not coorect!
> Signed-off-by: Boaz Harrosh <boaz@xxxxxxxxxxxxx>
> ---
> fs/direct-io.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 98040ba..2f024fc 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -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 */
Paul Bolle
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