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Commit 38815b78 authored by Sage Weil's avatar Sage Weil
Browse files

libceph: fix handling of short returns from get_user_pages 



get_user_pages() can return fewer pages than we ask for.  We were returning
a bogus pointer/error code in that case.  Instead, loop until we get all
the pages we want or get an error we can return to the caller.

Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent 16a8b70a

net/ceph/pagevec.c

+13 −5
Original line number Diff line number Diff line
@@ -16,22 +16,30 @@ struct page **ceph_get_direct_page_vector(const char __user *data, 
					  int num_pages, bool write_page)

{

	struct page **pages;

	int rc;

	int got = 0;

	int rc = 0;



	pages = kmalloc(sizeof(*pages) * num_pages, GFP_NOFS);

	if (!pages)

		return ERR_PTR(-ENOMEM);



	down_read(&current->mm->mmap_sem);

	rc = get_user_pages(current, current->mm, (unsigned long)data,

			    num_pages, write_page, 0, pages, NULL);

	while (got < num_pages) {

		rc = get_user_pages(current, current->mm,

		    (unsigned long)data + ((unsigned long)got * PAGE_SIZE),

		    num_pages - got, write_page, 0, pages + got, NULL);

		if (rc < 0)

			break;

		BUG_ON(rc == 0);

		got += rc;

	}

	up_read(&current->mm->mmap_sem);

	if (rc < num_pages)

	if (rc < 0)

		goto fail;

	return pages;



fail:

	ceph_put_page_vector(pages, rc > 0 ? rc : 0, false);

	ceph_put_page_vector(pages, got, false);

	return ERR_PTR(rc);

}

EXPORT_SYMBOL(ceph_get_direct_page_vector);