On Tue, 2013-06-04 at 08:59 -0400, Mikulas Patocka wrote: > > On Mon, 3 Jun 2013, Steven Rostedt wrote: > > > 3.6.11.5 stable review patch. > > If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Mikulas Patocka <[email protected]> > > > > [ Upstream commit 502624bdad3dba45dfaacaf36b7d83e39e74b2d2 ] > > > > This patch uses memalloc_noio_save to avoid a possible deadlock in > > dm-bufio. (it could happen only with large block size, at most > > PAGE_SIZE << MAX_ORDER (typically 8MiB). > > > > __vmalloc doesn't fully respect gfp flags. The specified gfp flags are > > used for allocation of requested pages, structures vmap_area, vmap_block > > and vm_struct and the radix tree nodes. > > > > However, the kernel pagetables are allocated always with GFP_KERNEL. > > Thus the allocation of pagetables can recurse back to the I/O layer and > > cause a deadlock. > > > > This patch uses the function memalloc_noio_save to set per-process > > PF_MEMALLOC_NOIO flag and the function memalloc_noio_restore to restore > > it. When this flag is set, all allocations in the process are done with > > implied GFP_NOIO flag, thus the deadlock can't happen. > > > > This should be backported to stable kernels, but they don't have the > > PF_MEMALLOC_NOIO flag and memalloc_noio_save/memalloc_noio_restore > > functions. So, PF_MEMALLOC should be set and restored instead. > > > > Signed-off-by: Mikulas Patocka <[email protected]> > > Cc: [email protected] > > Signed-off-by: Alasdair G Kergon <[email protected]> > > [ Set and clear PF_MEMALLOC manually - SR ] > > Signed-off-by: Steven Rostedt <[email protected]> > > --- > > drivers/md/dm-bufio.c | 26 +++++++++++++++++++++++++- > > 1 file changed, 25 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > > index c0fc827..a1f2487 100644 > > --- a/drivers/md/dm-bufio.c > > +++ b/drivers/md/dm-bufio.c > > @@ -321,6 +321,9 @@ static void __cache_size_refresh(void) > > static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, > > enum data_mode *data_mode) > > { > > + unsigned noio_flag; > > + void *ptr; > > + > > if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) { > > *data_mode = DATA_MODE_SLAB; > > return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask); > > @@ -334,7 +337,28 @@ static void *alloc_buffer_data(struct dm_bufio_client > > *c, gfp_t gfp_mask, > > } > > > > *data_mode = DATA_MODE_VMALLOC; > > - return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > > + > > + /* > > + * __vmalloc allocates the data pages and auxiliary structures with > > + * gfp_flags that were specified, but pagetables are always allocated > > + * with GFP_KERNEL, no matter what was specified as gfp_mask. > > + * > > + * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that > > + * all allocations done by this process (including pagetables) are done > > + * as if GFP_NOIO was specified. > > + */ > > + > > + if (gfp_mask & __GFP_NORETRY) { > > + noio_flag = current->flags; > > There should be noio_flag = current->flags & PF_MEMALLOC; because we don't > want to restore other flags.
Thanks for the review. Will fix. -- Steve > > > + current->flags |= PF_MEMALLOC; > > + } > > + > > + ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > > + > > + if (gfp_mask & __GFP_NORETRY) > > + current->flags = (current->flags & ~PF_MEMALLOC) | noio_flag; > > + > > + return ptr; > > } > > > > /* > > -- > > 1.7.10.4 > > Mikulas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
