Re: linux-next end of partition problems?

[Jens Axboe <jens.axboe@oracle.com>]

On Thu, Jun 04 2009, Jeff Moyer wrote:
> "Luck, Tony" <tony.luck@intel.com> writes:
> 
> >> What kind of controller/drive is this?
> >
> > lspci says the controller is:
> > 06:02.0 SCSI storage controller: LSI Logic / Symbios Logic 53c1030 PCI-X Fusion-MPT Dual Ultra320 SCSI (rev 07)
> >
> > console log says drive is:
> > scsi 0:0:1:0: Direct-Access     SEAGATE  ST318406LC       010A PQ: 0 ANSI: 3
> >  target0:0:1: Beginning Domain Validation
> >  target0:0:1: Ending Domain Validation
> >  target0:0:1: FAST-80 WIDE SCSI 160.0 MB/s DT (12.5 ns, offset 63)
> > sd 0:0:1:0: [sdb] 35843670 512-byte hardware sectors: (18.3 GB/17.0 GiB)
> > sd 0:0:1:0: [sdb] Write Protect is off
> > sd 0:0:1:0: [sdb] Mode Sense: 9f 00 10 08
> > scsi 0:0:6:0: Processor         ESG-SHV  SCA HSBP M17     1.0D PQ: 0 ANSI: 2
> >  target0:0:6: Beginning Domain Validation
> > sd 0:0:1:0: [sdb] Write cache: enabled, read cache: enabled, supports DPO and FUA
> >  target0:0:6: Ending Domain Validation
> >  target0:0:6: asynchronous
> >  sdb: sdb1 sdb2 sdb3
> > sd 0:0:1:0: [sdb] Attached SCSI disk
> >
> > A git bisect between v2.6.30-rc7(good) and next-20090602(bad) points
> > the finger at this commit (and reverting this change from next-20090602
> > confirms it introduces this problem):
> >
> >
> > commit db2dbb12dc47a50c7a4c5678f526014063e486f6
> > Author: Jeff Moyer <jmoyer@redhat.com>
> > Date:   Wed Apr 22 14:08:13 2009 +0200
> >
> >     block: implement blkdev_readpages
> >     
> >     Doing a proper block dev ->readpages() speeds up the crazy dump(8)
> >     approach of using interleaved process IO.
> >     
> >     Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
> >     Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> >
> > diff --git a/fs/block_dev.c b/fs/block_dev.c
> > index f45dbc1..a85fe31 100644
> > --- a/fs/block_dev.c
> > +++ b/fs/block_dev.c
> > @@ -331,6 +331,12 @@ static int blkdev_readpage(struct file * file, struct page * page)
> >  	return block_read_full_page(page, blkdev_get_block);
> >  }
> >  
> > +static int blkdev_readpages(struct file *file, struct address_space *mapping,
> > +			struct list_head *pages, unsigned nr_pages)
> > +{
> > +	return mpage_readpages(mapping, pages, nr_pages, blkdev_get_block);
> > +}
> > +
> >  static int blkdev_write_begin(struct file *file, struct address_space *mapping,
> >  			loff_t pos, unsigned len, unsigned flags,
> >  			struct page **pagep, void **fsdata)
> > @@ -1399,6 +1405,7 @@ static int blkdev_releasepage(struct page *page, gfp_t wait)
> >  
> >  static const struct address_space_operations def_blk_aops = {
> >  	.readpage	= blkdev_readpage,
> > +	.readpages	= blkdev_readpages,
> >  	.writepage	= blkdev_writepage,
> >  	.sync_page	= block_sync_page,
> >  	.write_begin	= blkdev_write_begin,
> >
> >
> > On a random hunch, I wondered whether this error message was connected to
> > the fact that ia64 kernel has a 64K page size.  I re-built using a 4k
> > pagesize ... and this also make the partition overrun message go away.
> >
> > So is it plausible that the blkdev_readpages() code is resulting in some
> > readahead of a page that overlaps the partition end?  The partition size
> > (15832057 * 1K block according to /proc/partitions) is not a multiple of
> > the 64K page size ... but then it isn't a multiple of 4K either :-(
> 
> Thanks for digging into this, Tony.  I'll take a look at it today.
> Jens, you can feel free to pull this for now.  I never did get you real
> data showing the improvement anyway, so I'll try to do that as well.

OK, I'll revert it for now.

-- 
Jens Axboe