On Tue, May 23, 2017 at 08:17:20AM -0400, Brian Foster wrote: > On Tue, May 23, 2017 at 07:08:32PM +0800, Eryu Guan wrote: > > On Tue, May 23, 2017 at 10:50:44AM +0200, Jan Kara wrote: > > > On Tue 23-05-17 11:21:23, Eryu Guan wrote: > > > > On Mon, May 22, 2017 at 01:50:47PM -0400, Brian Foster wrote: > > > > > On Thu, May 18, 2017 at 12:48:49PM +0200, Jan Kara wrote: > > > > > > There is an off-by-one error in loop termination conditions in > > > > > > xfs_find_get_desired_pgoff() since 'end' may index a page beyond end of > > > > > > desired range if 'endoff' is page aligned. It doesn't have any visible > > > > > > effects but still it is good to fix it. > > > > > > > > > > > > Signed-off-by: Jan Kara <jack@xxxxxxx> > > > > > > --- > > > > > > fs/xfs/xfs_file.c | 2 +- > > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > > > > > > index f371812e20c6..3714b5736fd3 100644 > > > > > > --- a/fs/xfs/xfs_file.c > > > > > > +++ b/fs/xfs/xfs_file.c > > > > > > @@ -1043,7 +1043,7 @@ xfs_find_get_desired_pgoff( > > > > > > > > > > > > index = startoff >> PAGE_SHIFT; > > > > > > endoff = XFS_FSB_TO_B(mp, map->br_startoff + map->br_blockcount); > > > > > > - end = endoff >> PAGE_SHIFT; > > > > > > + end = (endoff - 1) >> PAGE_SHIFT; > > > > > > > > > > Hmm.. I think this messes with the want count for the pagevec_lookup(). > > > > > E.g.: > > > > > > > > > > # xfs_io -fc "truncate 0" -c "falloc 0 16k" -c "pwrite 0 16k" -c "seek -h 0" /mnt/file > > > > > wrote 16384/16384 bytes at offset 0 > > > > > 16 KiB, 4 ops; 0.0000 sec (200.321 MiB/sec and 51282.0513 ops/sec) > > > > > Whence Result > > > > > HOLE 12288 > > > > > > > > I think the root cause is that the calculation for 'want' is wrong, it > > > > has an off-by-one bug too. I sent a patch[1] to fix it, with my patch > > > > applied on top of Jan's patchset, your test case passed (report HOLE at > > > > 16k). Can you please take a look if it's a correct fix? Thanks! > > > > > > Yes, I've messed that up. It is a bug introduced by my series as Brian > > > properly noticed. Thanks guys for noticing and fixing it! Darrick, should I > > > fold in Eryu's fix and send v4 of the series or will you just pick up > > > Eryu's fix? > > > > I think it's a separate bug, the issue described in my patch can be > > reproduced on stock 4.12-rc1 kernel, without your patchset. The > > situation for ext4 is similar to XFS, it seems not a bug introduced by > > your patches. > > > > Thanks for the review! > > > > I think there's the possiblity of multiple things going on here. The > problem noted above didn't occur without this series applied. Of course, > that doesn't mean that there isn't some other problem with the current > code that Eryu has reproduced and fixed. > > In any event, I don't think we should knowingly apply patches with > regressions, even if they are fixed up in the same patch series. Could > we get this fixed up/combined somehow or another so we at least do not > introduce a transient regression (it doesn't matter to me if the > independent problem is addressed in a separate patch or at the same > time)? > > Also, Eryu, could you Tested-by this series before it goes in? It seems > you have some tests that stress it quite thoroughly. :) I have no tests more than generic/285 and generic/436, I just run them with different block size xfs/ext4 and on different architectures (x86_64 and ppc64) :) But sure, I'll give a Tested-by tag once we work out which patches should go in. Thanks, Eryu -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
