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mm: replace get_user_pages_remote() write/force parameters with gup_flags

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This removes the 'write' and 'force' from get_user_pages_remote() and
replaces them with 'gup_flags' to make the use of FOLL_FORCE explicit in
callers as use of this flag can result in surprising behaviour (and
hence bugs) within the mm subsystem.

Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
2016-10-13 01:20:17 +01:00
committed by Linus Torvalds
parent 768ae309a9
commit 9beae1ea89
9 changed files with 40 additions and 27 deletions
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22
mm/gup.c
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@@ -915,9 +915,7 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
* @mm: mm_struct of target mm
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @write: whether pages will be written to by the caller
* @force: whether to force access even when user mapping is currently
* protected (but never forces write access to shared mapping).
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
@@ -946,9 +944,9 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
* or similar operation cannot guarantee anything stronger anyway because
* locks can't be held over the syscall boundary.
*
* If write=0, the page must not be written to. If the page is written to,
* set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
* after the page is finished with, and before put_page is called.
* If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
* is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
* be called after the page is finished with, and before put_page is called.
*
* get_user_pages is typically used for fewer-copy IO operations, to get a
* handle on the memory by some means other than accesses via the user virtual
@@ -965,18 +963,12 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
*/
long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
int write, int force, struct page **pages,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas)
{
unsigned int flags = FOLL_TOUCH | FOLL_REMOTE;
if (write)
flags |= FOLL_WRITE;
if (force)
flags |= FOLL_FORCE;
return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
NULL, false, flags);
NULL, false,
gup_flags | FOLL_TOUCH | FOLL_REMOTE);
}
EXPORT_SYMBOL(get_user_pages_remote);

6
mm/memory.c
View File

@@ -3873,6 +3873,10 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
{
struct vm_area_struct *vma;
void *old_buf = buf;
unsigned int flags = FOLL_FORCE;
if (write)
flags |= FOLL_WRITE;
down_read(&mm->mmap_sem);
/* ignore errors, just check how much was successfully transferred */
@@ -3882,7 +3886,7 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
struct page *page = NULL;
ret = get_user_pages_remote(tsk, mm, addr, 1,
write, 1, &page, &vma);
flags, &page, &vma);
if (ret <= 0) {
#ifndef CONFIG_HAVE_IOREMAP_PROT
break;