From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Arnd Bergmann To: Jens Axboe Cc: Omar Sandoval , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sbitmap: avoid maybe-uninitialized warning Date: Mon, 19 Sep 2016 17:14:48 +0200 Message-ID: <2163656.5SLNssdXj1@wuerfel> In-Reply-To: <6efcc3e0-b85f-9612-2562-d37922a1dc92@kernel.dk> References: <20160919123359.1225305-1-arnd@arndb.de> <6efcc3e0-b85f-9612-2562-d37922a1dc92@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" List-ID: On Monday, September 19, 2016 8:43:12 AM CEST Jens Axboe wrote: > On 09/19/2016 06:33 AM, Arnd Bergmann wrote: > > The sbitmap code that has just been turned into a library module > > returns uninitialized data for sbitmap_weight(), as pointed out by > > gcc when building with -Wmaybe-uninitialized: > > > > lib/sbitmap.c: In function 'sbitmap_weight': > > lib/sbitmap.c:179:9: error: 'weight' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > > > Note that the value is never initialized, we just add data on > > top, so it is wrong regardless of sb->map_nr. > > > > This adds the missing initialization. > > Thanks Arnd, Colin sent the same patch and I applied it. Note that: Ok, thanks! > > Fixes: 88459642cba4 ("blk-mq: abstract tag allocation out into sbitmap library") > > that isn't truly correct, that patch is just what moved the code. The > bug predates that commit. It's not important as long as the bug is fixed now, but I think it was correct before that move, we just lost the 'used=0' initialization, which also triggered the warning: -static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt) -{ - unsigned int i, used; - - for (i = 0, used = 0; i < bt->map_nr; i++) { - struct blk_align_bitmap *bm = &bt->map[i]; - - used += bitmap_weight(&bm->word, bm->depth); } - return bt->depth - used; } Arnd