On 07/17/2014 12:48 PM, Paul Bolle wrote:
> 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!
Sorry you are absolutely right, I only saw this after "send", is why
I ping you to make sure.
I have reviewed it fully, your initial code is correct *and tested).
Here is a new V2 patch without your sign-off
Thanks
Boaz
>
>> 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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