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Message-ID: <1405590510.4808.16.camel@x220> Date: Thu, 17 Jul 2014 11:48:30 +0200 From: Paul Bolle <pebolle@...cali.nl> To: Boaz Harrosh <openosd@...il.com> Cc: Christoph Hellwig <hch@...radead.org>, viro@...iv.linux.org.uk, Borislav Petkov <bp@...en8.de>, Sam Ravnborg <sam@...nborg.org>, pramod.gurav.etc@...il.com, Jason Cooper <jason@...edaemon.net>, Markus Mayer <markus.mayer@...aro.org>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: direct-io: squelch maybe-uninitialized warning in do_direct_IO() Boaz, On Thu, 2014-07-17 at 12:37 +0300, Boaz Harrosh wrote: > From: Paul Bolle <pebolle@...cali.nl> > > 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@...cali.nl> This is simply not coorect! > Signed-off-by: Boaz Harrosh <boaz@...xistor.com> > --- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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