Messages in this thread | | | Date | Sun, 19 Aug 2012 12:23:15 +0200 | From | Marco Stornelli <> | Subject | Re: [PATCH 2/3] writeback: fix incorrect return value type of bdi_dirty_limit |
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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
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