[PATCH] loop: Fix OOM and oops

The loop driver takes a copy of the data which it is writing.  When this
happens on the try_to_free_pages() path, loop can easily consume ALL memory
and bio_copy() will fail to allocate a page.

Loop forgets to check the bio_copy() return value and oopses.

Fix this by dropping PF_MEMALLOC and throttling to the block writeout speed.

The patch exports blk_congestion_wait() to modules for this.  This is a
needed export: several filesystems have a "try to allocate and yield if it
failed" loop and blk_congestion_wait() is a more appropriate way of
implementing the sleep in this situation.

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/ksyms.c b/kernel/ksyms.c
index f30934957b82..aff3e9298b77 100644
--- a/kernel/ksyms.c
+++ b/kernel/ksyms.c
@@ -119,6 +119,7 @@ EXPORT_SYMBOL(find_vma);
 EXPORT_SYMBOL(get_unmapped_area);
 EXPORT_SYMBOL(init_mm);
 EXPORT_SYMBOL(blk_queue_bounce);
+EXPORT_SYMBOL(blk_congestion_wait);
 #ifdef CONFIG_HIGHMEM
 EXPORT_SYMBOL(kmap_high);
 EXPORT_SYMBOL(kunmap_high);