Messages in this thread | | | Date | Sun, 19 Aug 2012 12:35:42 +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 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
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