Messages in this thread | | | Date | Wed, 22 Jul 2015 15:46:16 +0200 | From | Jerome Marchand <> | Subject | Re: [RFC PATCH] nfs: avoid swap-over-NFS deadlock |
| |
On 07/22/2015 02:23 PM, Trond Myklebust wrote: > On Wed, Jul 22, 2015 at 4:10 AM, Jerome Marchand <jmarchan@redhat.com> wrote: >> >> Lockdep warns about a inconsistent {RECLAIM_FS-ON-W} -> >> {IN-RECLAIM_FS-W} usage. The culpritt is the inode->i_mutex taken in >> nfs_file_direct_write(). This code was introduced by commit a9ab5e840669 >> ("nfs: page cache invalidation for dio"). >> This naive test patch avoid to take the mutex on a swapfile and makes >> lockdep happy again. However I don't know much about NFS code and I >> assume it's probably not the proper solution. Any thought? >> >> Signed-off-by: Jerome Marchand <jmarchan@redhat.com> > > NFS is not the only O_DIRECT implementation to set the inode->i_mutex. > Why can't this be fixed in the generic swap code instead of adding > yet-another-exception-for-IS_SWAPFILE?
I meant to cc Mel. Just added him.
AFAIK NFS is the only filesystem that uses swap_activate. Other swapfiles are handled more or less like block device (divided in a set of contiguous ranges of disk block called swap extents), so there are not affected by this possible deadlock.
Also nfs_direct_IO() is special in that it is called only from swap, nfs_file_direct_write() however has other users.
Jerome > > Cheers > Trond >
[unhandled content-type:application/pgp-signature] | |