> 在 2017年12月23日,12:16,十刀 <shidao.ytt@xxxxxxxxxxxxxxx> 写道: > > From: "shidao.ytt" <shidao.ytt@xxxxxxxxxxxxxxx> > > in commit 441c228f817f7 ("mm: fadvise: document the > fadvise(FADV_DONTNEED) behaviour for partial pages") Mel Gorman > explained why partial pages should be preserved instead of discarded > when using fadvise(FADV_DONTNEED), however the actual codes to calcuate > end_index was unexpectedly wrong, the code behavior didn't match to the > statement in comments; Luckily in another commit 18aba41cbf > ("mm/fadvise.c: do not discard partial pages with POSIX_FADV_DONTNEED") > Oleg Drokin fixed this behavior > > Here I come up with a new idea that actually we can still discard the > last parital page iff the page-unaligned endbyte is also the end of > file, since no one else will use the rest of the page and it should be > safe enough to discard. +akpm... Hi Mel, Andrew: Would you please take a look at this patch, to see if this proposal is reasonable enough, thanks in advance! Thanks, Caspar > > Signed-off-by: shidao.ytt <shidao.ytt@xxxxxxxxxxxxxxx> > Signed-off-by: Caspar Zhang <jinli.zjl@xxxxxxxxxxxxxxx> > --- > mm/fadvise.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/fadvise.c b/mm/fadvise.c > index ec70d6e..f74b21e 100644 > --- a/mm/fadvise.c > +++ b/mm/fadvise.c > @@ -127,7 +127,8 @@ > */ > start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT; > end_index = (endbyte >> PAGE_SHIFT); > - if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK) { > + if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK && > + endbyte != inode->i_size - 1) { > /* First page is tricky as 0 - 1 = -1, but pgoff_t > * is unsigned, so the end_index >= start_index > * check below would be true and we'll discard the whole > -- > 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href