Messages in this thread | | | Date | Wed, 07 Oct 2009 09:25:06 +0530 | From | Suresh Jayaraman <> | Subject | Re: [PATCH] swapfile: avoid NULL pointer dereference in swapon when s_bdev is NULL |
| |
Hugh Dickins wrote: > On Thu, 1 Oct 2009, Suresh Jayaraman wrote: >> Hugh Dickins wrote: >>> On Thu, 1 Oct 2009, Suresh Jayaraman wrote: >>>> The call sequence is add_to_swap() -> get_swap_page() -> scan_swap_map() >>>> -> discard_swap_cluster() -> blkdev_issue_discard(). >>>> >>>> Wrapping the code around a NULL check fixes the Oops for me. >>> That's odd: scan_swap_map() should only discard_swap_cluster() if >>> SWP_DISCARDABLE got set, and your first patch made sure that it wasn't. >> I forgot to mention, this is not on loopback NFS mount but an remote NFS >> mount (so possibly s_bdev is not NULL) when doing swapon. The oops was >> triggered when memhog program tries to use the swap space on the newly >> created swapfile on NFS. I have not completely investigated the issue, >> perhaps s_bdev is not being set when it ought to be.. > > I'm happy to see your first patch already in 2.6.32-rc3, but still > suspicious of this second patch you sent afterwards. A quick skim > through your patchset suggests 23/31 is probably responsible:
Thanks for skimming through those patches. I noticed this already during my review and thought I had already fixed this, but apparently I missed out. I'll test after fixing this and report.
> --- mmotm.orig/include/linux/swap.h > +++ mmotm/include/linux/swap.h > @@ -120,6 +120,7 @@ struct swap_extent { > enum { > SWP_USED = (1 << 0), /* is slot in swap_info[] used? */ > SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */ > + SWP_FILE = (1 << 2), /* file swap area */ > SWP_DISCARDABLE = (1 << 2), /* blkdev supports discard */ > SWP_DISCARDING = (1 << 3), /* now discarding a free cluster */ > SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */ > > Hugh
Thanks,
-- Suresh Jayaraman
| |