Commit 29da03f1 authored by Andrew Morton's avatar Andrew Morton Committed by David S. Miller

[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.
parent 159b5855
...@@ -447,7 +447,22 @@ static struct bio *loop_get_buffer(struct loop_device *lo, struct bio *rbh) ...@@ -447,7 +447,22 @@ static struct bio *loop_get_buffer(struct loop_device *lo, struct bio *rbh)
goto out_bh; goto out_bh;
} }
bio = bio_copy(rbh, GFP_NOIO, rbh->bi_rw & WRITE); /*
* When called on the page reclaim -> writepage path, this code can
* trivially consume all memory. So we drop PF_MEMALLOC to avoid
* stealing all the page reserves and throttle to the writeout rate.
* pdflush will have been woken by page reclaim. Let it do its work.
*/
do {
int flags = current->flags;
current->flags &= ~PF_MEMALLOC;
bio = bio_copy(rbh, (GFP_ATOMIC & ~__GFP_HIGH) | __GFP_NOWARN,
rbh->bi_rw & WRITE);
current->flags = flags;
if (bio == NULL)
blk_congestion_wait(WRITE, HZ/10);
} while (bio == NULL);
bio->bi_end_io = loop_end_io_transfer; bio->bi_end_io = loop_end_io_transfer;
bio->bi_private = rbh; bio->bi_private = rbh;
......
...@@ -119,6 +119,7 @@ EXPORT_SYMBOL(find_vma); ...@@ -119,6 +119,7 @@ EXPORT_SYMBOL(find_vma);
EXPORT_SYMBOL(get_unmapped_area); EXPORT_SYMBOL(get_unmapped_area);
EXPORT_SYMBOL(init_mm); EXPORT_SYMBOL(init_mm);
EXPORT_SYMBOL(blk_queue_bounce); EXPORT_SYMBOL(blk_queue_bounce);
EXPORT_SYMBOL(blk_congestion_wait);
#ifdef CONFIG_HIGHMEM #ifdef CONFIG_HIGHMEM
EXPORT_SYMBOL(kmap_high); EXPORT_SYMBOL(kmap_high);
EXPORT_SYMBOL(kunmap_high); EXPORT_SYMBOL(kunmap_high);
......
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