Re: [PATCH v2 1/4] kernfs: kvmalloc xattr value instead of kmalloc

On Fri, Mar 06, 2020 at 12:49:51AM -0800, Joe Perches wrote:

On Thu, 2020-03-05 at 13:16 -0800, Daniel Xu wrote:

quoted

It's not really necessary to have contiguous physical memory for xattr
values. We no longer need to worry about higher order allocations
failing with kvmalloc, especially because the xattr size limit is at
64K.

So why use vmalloc memory at all?

quoted

diff --git a/fs/xattr.c b/fs/xattr.c

']

quoted

@@ -817,7 +817,7 @@ struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 	if (len < sizeof(*new_xattr))
 		return NULL;
 
-	new_xattr = kmalloc(len, GFP_KERNEL);
+	new_xattr = kvmalloc(len, GFP_KERNEL);

Why is this sensible?

See the thread on v1

vmalloc memory is a much more limited resource.

Large chunks of "len" is much more limited :)

thanks,

greg k-h