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Fri, 21 Feb 2020 15:35:52 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=+ZsaQJllFuL8jpNObDQrHmpdC/B73n9RqMvE0qPHxaM=; b=e19h/tTJERLUFpOL5Gva3Nh5/X wd0VH9aVgKh+1Blgs+9Q15ijaVkaoTLAy7WypYckq6maI2+/Qpa5TYpUzL45zkwW6/rKVd4gOa/Q3 37XTTlJ3n85F+yMLVB8w0BnbSlS+Y+mVNSOJqRCX3b4kHG/mSGnd+/RHhL7LSbdq0PycpO3gHljyg 1ePLpWP66QKkQwSW3hqI4AmWyW4KZvprzI+VqeFwh8xfQgZxihaUIj3MuUi6DWndVunwNc8HfQSPa cJzgSNpVLmszdlcuXvTGALnsMeU2uXmuwM6kJU9UgfbmbAX46oAsryhNENVSPO0btKS8JfbqGc1YR ErE1c+gA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j5AL3-00062c-43; Fri, 21 Feb 2020 15:35:37 +0000 Date: Fri, 21 Feb 2020 07:35:37 -0800 From: Matthew Wilcox To: John Hubbard Message-ID: <20200221153537.GE24185@bombadil.infradead.org> References: <20200219210103.32400-1-willy@infradead.org> <20200219210103.32400-12-willy@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Headers-End: 1j5ALE-003PUh-J2 Subject: Re: [f2fs-dev] [PATCH v7 11/24] mm: Move end_index check out of readahead loop X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-mm@kvack.org, ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Thu, Feb 20, 2020 at 07:50:39PM -0800, John Hubbard wrote: > This tiny patch made me pause, because I wasn't sure at first of the exact > intent of the lines above. Once I worked it out, it seemed like it might > be helpful (or overkill??) to add a few hints for the reader, especially since > there are no hints in the function's (minimal) documentation header. What > do you think of this? > > /* > * If we can't read *any* pages without going past the inodes's isize > * limit, give up entirely: > */ > if (index > end_index) > return; > > /* Cap nr_to_read, in order to avoid overflowing the ULONG type: */ > if (index + nr_to_read < index) > nr_to_read = ULONG_MAX - index + 1; > > /* Cap nr_to_read, to avoid reading past the inode's isize limit: */ > if (index + nr_to_read >= end_index) > nr_to_read = end_index - index + 1; A little verbose for my taste ... How about this? end_index = (isize - 1) >> PAGE_SHIFT; if (index > end_index) return; /* Avoid wrapping to the beginning of the file */ if (index + nr_to_read < index) nr_to_read = ULONG_MAX - index + 1; /* Don't read past the page containing the last byte of the file */ if (index + nr_to_read >= end_index) nr_to_read = end_index - index + 1; _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel