On Sat, May 17, 2008 at 02:17:37PM -0700, Linus Torvalds wrote:
quoted text
> > [4294293.003500]  [<ffffffff8028106a>] __kmalloc+0x3e/0xe6
> > [4294293.003500]  [<ffffffff803067fc>] ? xfs_iflush_int+0x272/0x2fb
> > [4294293.003500]  [<ffffffff80320552>] kmem_alloc+0x6a/0xd1
> > [4294293.003500]  [<ffffffff80307a9c>] xfs_iflush_cluster+0x4b/0x33f
> > [4294293.003500]  [<ffffffff8030681e>] ? xfs_iflush_int+0x294/0x2fb
> > [4294293.003500]  [<ffffffff80307f4b>] xfs_iflush+0x1bb/0x29d
> > [4294293.003500]  [<ffffffff8031bc30>] xfs_inode_flush+0xb8/0xdd
> > [4294293.003500]  [<ffffffff80328b1f>] xfs_fs_write_inode+0x30/0x4c
> 
> And as a result, all the XFS stuff is then waiting for that lock which is 
> held by pdflush above:

Btw, just that function has a missing GFP_NOFS and a too large
allocation which were fixed by Dave Chinner but aren't in mainline
yet.  Can you check whether it still happens with the patch below?