Messages in this thread | | | Date | Sun, 10 Dec 2000 22:55:29 +0100 | From | Miloslav Trmac <> |
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Hi, On Sun, Dec 10, 2000 at 03:30:41PM -0500, Alexander Viro wrote: > On Sun, 10 Dec 2000, Miloslav Trmac wrote: > > Hi, > > vmtruncate () in test11 doesn't clear ends of partial pages. Patch is attached > > It doesn't and it shouldn't. That's done in ->truncate(). Check ext2_truncate() > for example. ext2_truncate () (or block_truncate_page (), to be precise) clears end of page-cache page. partial_clear () in mm/memory.c is IMHO supposed to clear ends of anonymous pages (created from COW on MAP_PRIVATE mappings). I wasn't adding any new functionality, just correcting the old implementation (which would never trigger).
[Yes, currently it would clear the end of the page-cache page as many times as the page is accessible trough a pte. partial_clear () should probably clear *only* anonymous and swap pages.]
Actually, I'm not that sure that MAP_PRIVATE partial pages should be cleared; SuSv2 only says "the whole pages beyond the new end will be discarded" [ftruncate ()] and "It is unspecified whether modifications to the underlying object done after the MAP_PRIVATE mapping is established are visible through the MAP_PRIVATE mapping." [mmap ()]. So maybe not clearing the pages is The Right Thing - especially as it avoids the trouble with swapped-out pages. Remove partial_clear () completely, then. Mirek Trmac - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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