Re: [PATCH] fdtable: Avoid triggering OOMs from alloc_fdmem

Cong Wang [off-list ref] writes:

On Mon, Feb 3, 2014 at 9:26 PM, Eric W. Biederman [off-list ref] wrote:

quoted

diff --git a/fs/file.c b/fs/file.c
index 771578b33fb6..db25c2bdfe46 100644
--- a/fs/file.c
+++ b/fs/file.c

@@ -34,7 +34,7 @@ static void *alloc_fdmem(size_t size)
         * vmalloc() if the allocation size will be considered "large" by the VM.
         */
        if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
-               void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN);
+               void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY);
                if (data != NULL)
                        return data;
        }

Or try again without __GFP_NORETRY like we do in nelink mmap?

I think I would much rather keep the current semantics of return -ENOMEM
and keep the problem localized then trigger a box wide OOM thank you
very much.


Retrying the kmalloc without __GFP_NORETRY is pointless.  If you are in
the unlikely 0.01% of the time when the kmalloc fails it is almost
certainly going to fail again.  Writing out_of_memory() as kmalloc()
is pointless and very confusing.

The vmalloc won't fail unless you are on a 32bit box.  So it isn't a
case that anyone has to deal with in practice.

Eric

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>