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Mon, 18 Sep 2023 14:17:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id c2yRIPNbCGUDMgAAMHmgww (envelope-from ); Mon, 18 Sep 2023 14:17:23 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 9362BA0759; Mon, 18 Sep 2023 16:17:22 +0200 (CEST) Date: Mon, 18 Sep 2023 16:17:22 +0200 From: Jan Kara To: Mirsad Todorovac Cc: Jan Kara , Philipp Stanner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox , Chris Mason , Andrew Morton , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, linux-mm@kvack.org, Yury Norov Subject: Re: [PATCH v1 1/1] xarray: fix the data-race in xas_find_chunk() by using READ_ONCE() Message-ID: <20230918141722.gasntomhkkp2fwy2@quack3> References: <20230918044739.29782-1-mirsad.todorovac@alu.unizg.hr> <20230918094116.2mgquyxhnxcawxfu@quack3> <22ca3ad4-42ef-43bc-51d0-78aaf274977b@alu.unizg.hr> <20230918113840.h3mmnuyer44e5bc5@quack3> <20230918131815.otjqgu3zhigsst64@quack3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 865FB40013 X-Stat-Signature: mbij9zqewgsgij5iqnm3xn88hx3djgkm X-HE-Tag: 1695046645-714310 X-HE-Meta: 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 mfKH/o7b NBnUMzxxFW7XD/kiTwD54JzHoz1B0y3uJ2TvXIMLxyZJ/yzzP63v8ekHsNemJ6N6Z/8rnj0fi+FWtH/ZvX4zJ1mEUY9UONonPjS/H7WMYwy/BRc6ChP0Gyudi/DTNr999Sqe9rhE7OK3jcrxUY6+jNaXZRcK7m38Pq7TqLvA+5FOREhlfAPAIyzKaYHruqktEC3pYywbE2/uhqn+7QsedqDIMCD6DCxasH3HmC1njHhoQ9HwJyv5NZ5bq5eTHMTmlGXjz5nDPoSj0xjcPKcZa5WYmvqz17Hjmoe2QjDgk4bROc5pjzp8B7KYyyAcwu0qIEWRXvGNtkbOuy4agKZYiv7GwvGwdUxl20zNm9MlDRK6PTdW+Wm+tSP4r8Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon 18-09-23 15:34:46, Mirsad Todorovac wrote: > On 9/18/23 15:18, Jan Kara wrote: > > On Mon 18-09-23 14:46:02, Mirsad Todorovac wrote: > > > Hi, > > > > > > I tried this patch and the > > > > > > > > 95 _find_first_and_bit (lib/find_bit.c:114 (discriminator 10)) > > > > > 31 _find_first_zero_bit (lib/find_bit.c:125 (discriminator 10)) > > > > > 173 _find_next_and_bit (lib/find_bit.c:171 (discriminator 2)) > > > > > 655 _find_next_bit (lib/find_bit.c:133 (discriminator 2)) > > > > > 5 _find_next_zero_bit > > > > > > data-races do not seem to appear any longer. > > > > Yup. You've just missed one case in _find_last_bit() and then all the > > functions in include/linux/find.h need a similar treatment... > > I seem to have this: > > ----------------------------------------------------------------------------------- > #ifndef find_last_bit > unsigned long _find_last_bit(const unsigned long *addr, unsigned long size) > { > if (size) { > unsigned long val = BITMAP_LAST_WORD_MASK(size); > unsigned long idx = (size-1) / BITS_PER_LONG; > > do { > val &= READ_ONCE(addr[idx]); > if (val) > return idx * BITS_PER_LONG + __fls(val); > > val = ~0ul; > } while (idx--); > } > return size; > } > EXPORT_SYMBOL(_find_last_bit); > #endif > ----------------------------------------------------------------------------------- > > Is there something I did not notice? No, this looks correct. I just somehow didn't see this hunk in the diff you've posted. Honza -- Jan Kara SUSE Labs, CR