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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: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil 2011-03-02 16:55:21 -08:00
parent 16a8b70a5a
commit 38815b7802
1 changed files with 13 additions and 5 deletions
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18
net/ceph/pagevec.c
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@ -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);