On Thu, 22 Apr 2021, Andrew Morton wrote: > On Thu, 22 Apr 2021 13:48:57 -0700 (PDT) Hugh Dickins <hughd@xxxxxxxxxx> wrote: > > > Andrew, I'd have just sent a -fix.patch to remove the unnecessary u64s, > > but need to reword the commit message: so please replace yesterday's > > mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit.patch > > by this one - thanks. > > Actually, I routinely update the base patch's changelog when queueing a -fix. And thank you for that, but if there's time, I think we would still prefer the final commit message to include corrections where Matthew enlightened me (that "sign-extension" claim came from my confusion): -u64 casts added to stop unfortunate sign-extension when shifting (and -let's use shifts throughout, rather than mixed with * and /). - -Use round_up() when advancing pos, to stop assuming that pos was already -THP-aligned when advancing it by THP-size. (But I believe this use of -round_up() assumes that any THP must be THP-aligned: true while tmpfs -enforces that alignment, and is the only fs with FS_THP_SUPPORT; but might -need to be generalized in the future? If I try to generalize it right -now, I'm sure to get it wrong!) +u64 cast to stop losing bits when converting unsigned long to loff_t +(and let's use shifts throughout, rather than mixed with * and /). + +Use round_up() when advancing pos, to stop assuming that pos was +already THP-aligned when advancing it by THP-size. (This use of +round_up() assumes that any THP has THP-aligned index: true at present +and true going forward, but could be recoded to avoid the assumption.) Thanks, Hugh
