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Message-ID: <5030C17E.5050906@gmail.com> Date: Sun, 19 Aug 2012 12:35:42 +0200 From: Marco Stornelli <marco.stornelli@...il.com> To: Fengguang Wu <fengguang.wu@...el.com> CC: Namjae Jeon <linkinjeon@...il.com>, akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org Subject: Re: [PATCH 2/3] writeback: fix incorrect return value type of bdi_dirty_limit Il 19/08/2012 12:23, Marco Stornelli ha scritto: > Il 19/08/2012 04:17, Fengguang Wu ha scritto: >> On Sat, Aug 18, 2012 at 05:49:21AM -0400, Namjae Jeon wrote: >>> unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned >>> long dirty) >>> >>> Above function return type is unsigned long, but return value is >>> kept in "u64 bdi_dirty". >>> It can return incorrect value by type casting. >> >> I don't see how the cast can return wrong value. >> The u64 is necessary for the intermediate calculations. >> >> Thanks, >> Fengguang >> > > We are sure u64 is 8byte long, but unsigned long is 4byte long on 32-bit > machine, so if bdi_dirty can assume values bigger than 2^32 there is an > implicit truncate of its value, isn't it? > > Marco Sorry but I didn't see the code, it seems not possible so the wrong situation can't happen. Maybe we can simply add a comment, nothing more. Marco -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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