Commit 6fcc5420 authored by Boaz Harrosh's avatar Boaz Harrosh Committed by Christoph Hellwig

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: default avatarBoaz Harrosh <>
Signed-off-by: default avatarChristoph Hellwig <>
parent 82e13c71
......@@ -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;
while (from < to) {
unsigned this_chunk_bytes; /* # of bytes mapped */
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