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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1689846435; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dQrUdY1vRsj8E+dCm96975wE2JF9r7J+GLmQavXqC6U=; b=ppP0xq24ptj/OlMY3SPOuHL6Ff4dQYJc12lo4pwlHFUru/0kT+yUO+nGANDCOXMijpY0zh 0xRV/YP9illwyEGWdRzcnR+C2a2oqd4/o3nAXfqCCcJ3QCVAM4J4lj3lf7TdGBwhgX25Kc aqsmNNgQe9Mnd4K/gYhs9jp73e9/KfE= From: chengming.zhou@linux.dev To: axboe@kernel.dk, osandov@fb.com, ming.lei@redhat.com, kbusch@kernel.org, krisman@suse.de Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, zhouchengming@bytedance.com Subject: [PATCH 1/6] sbitmap: fix hint wrap in the failure case Date: Thu, 20 Jul 2023 17:45:50 +0800 Message-ID: <20230720094555.1397621-2-chengming.zhou@linux.dev> In-Reply-To: <20230720094555.1397621-1-chengming.zhou@linux.dev> References: <20230720094555.1397621-1-chengming.zhou@linux.dev> MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1771938066399285971 X-GMAIL-MSGID: 1771938066399285971 From: Chengming Zhou ``` hint = nr + 1; if (hint >= depth - 1) hint = 0; ``` Now we wrap the hint to 0 in the failure case, but: 1. hint == depth - 1, is actually an available offset hint, which we shouldn't wrap hint to 0. 2. In the strict round_robin non-wrap case, we shouldn't wrap at all. ``` wrap = wrap && hint; ``` We only need to check wrap based on the original hint ( > 0), don't need to recheck the new hint which maybe updated in the failure case. Also delete the mismatched comments by the way. Signed-off-by: Chengming Zhou --- lib/sbitmap.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/lib/sbitmap.c b/lib/sbitmap.c index eff4e42c425a..5ed6c2adf58e 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -144,12 +144,7 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth, while (1) { nr = find_next_zero_bit(word, depth, hint); if (unlikely(nr >= depth)) { - /* - * We started with an offset, and we didn't reset the - * offset to 0 in a failure case, so start from 0 to - * exhaust the map. - */ - if (hint && wrap) { + if (wrap) { hint = 0; continue; } @@ -160,8 +155,13 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth, break; hint = nr + 1; - if (hint >= depth - 1) - hint = 0; + if (hint >= depth) { + if (wrap) { + hint = 0; + continue; + } + return -1; + } } return nr;