From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Hubbard Date: Fri, 21 Feb 2020 11:41:28 -0800 Subject: [Ocfs2-devel] [PATCH v7 11/24] mm: Move end_index check out of readahead loop In-Reply-To: <20200221153537.GE24185@bombadil.infradead.org> References: <20200219210103.32400-1-willy@infradead.org> <20200219210103.32400-12-willy@infradead.org> <20200221153537.GE24185@bombadil.infradead.org> Message-ID: <1fd052ce-cd5e-60ce-e494-cbf6427d3ed3@nvidia.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org On 2/21/20 7:35 AM, Matthew Wilcox wrote: > 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? Mine too, actually. :) I think your version below looks good. thanks, -- John Hubbard NVIDIA > > 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; >