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Date: Sat, 29 May 2010 21:26:47 +0800 From: Changli Gao <xiaosuo@...il.com> To: Borislav Petkov <bp@...en8.de>, Changli Gao <xiaosuo@...il.com>, Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/2] fs: optimize mpage_readpage() On Sat, May 29, 2010 at 8:10 PM, Borislav Petkov <bp@...en8.de> wrote: > From: Changli Gao <xiaosuo@...il.com> > Date: Sat, May 29, 2010 at 09:18:46AM +0800 > >> optimize mpage_readpage() >> >> we don't need to initialize bio, and pass it to do_mpage_readpage() as >> parameter, as it is returned by do_mpage_readpage(). >> >> Signed-off-by: Changli Gao <xiaosuo@...il.com> >> ---- >> fs/mpage.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> diff --git a/fs/mpage.c b/fs/mpage.c >> index fd56ca2..94ff0d1 100644 >> --- a/fs/mpage.c >> +++ b/fs/mpage.c >> @@ -409,14 +409,14 @@ EXPORT_SYMBOL(mpage_readpages); >> */ >> int mpage_readpage(struct page *page, get_block_t get_block) >> { >> - struct bio *bio = NULL; >> + struct bio *bio; >> sector_t last_block_in_bio = 0; >> struct buffer_head map_bh; >> unsigned long first_logical_block = 0; >> >> map_bh.b_state = 0; >> map_bh.b_size = 0; >> - bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio, >> + bio = do_mpage_readpage(NULL, page, 1, &last_block_in_bio, >> &map_bh, &first_logical_block, get_block); >> if (bio) >> mpage_bio_submit(READ, bio); > > Nope, I don't think that's a good idea. > > On the one hand, this is a trick to shut up gcc: > > fs/mpage.c: In function ‘mpage_readpage’: > fs/mpage.c:419: warning: ‘bio’ is used uninitialized in this function > > and, on the other hand, make sure bio is NULL and not some random stack > value since bio is explicitly checked for NULL in do_mpage_readpage(). > Did the compiler warning appear after applying my patch? It doesn't happen when I testing it. And I don't pass bio to do_mpage_readpage(), but I pass NULL instead. -- Regards, Changli Gao(xiaosuo@...il.com) -- 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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