The patch titled
Subject: mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions-v3
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions-v3.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions-v3.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions-v3
Date: Fri, 18 Oct 2024 15:34:11 -0700
1) Applied the fix to check_and_migrate_movable_pages(), instead of its
caller, as per David Hildenbrand's suggestion (thanks!).
2) Dropped Alistair's reviewed-by tag, because the fix has changed.
3) Reworked the relevant documentation, and commit description.
Link: https://lkml.kernel.org/r/20241018223411.310331-1-jhubbard@xxxxxxxxxx
Fixes: 24a95998e9ba ("mm/gup.c: simplify and fix check_and_migrate_movable_pages() return codes")
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Dongwon Kim <dongwon.kim@xxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Junxiao Chang <junxiao.chang@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 33 +++++++++++++++++++--------------
1 file changed, 19 insertions(+), 14 deletions(-)
--- a/mm/gup.c~mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions-v3
+++ a/mm/gup.c
@@ -2394,20 +2394,25 @@ err:
}
/*
- * Check whether all folios are *allowed* to be pinned indefinitely (longterm).
+ * Check whether all folios are *allowed* to be pinned indefinitely (long term).
* Rather confusingly, all folios in the range are required to be pinned via
* FOLL_PIN, before calling this routine.
*
- * If any folios in the range are not allowed to be pinned, then this routine
- * will migrate those folios away, unpin all the folios in the range and return
- * -EAGAIN. The caller should re-pin the entire range with FOLL_PIN and then
- * call this routine again.
+ * Return values:
*
- * If an error other than -EAGAIN occurs, this indicates a migration failure.
- * The caller should give up, and propagate the error back up the call stack.
- *
- * If everything is OK and all folios in the range are allowed to be pinned,
+ * 0: if everything is OK and all folios in the range are allowed to be pinned,
* then this routine leaves all folios pinned and returns zero for success.
+ *
+ * -EAGAIN: if any folios in the range are not allowed to be pinned, then this
+ * routine will migrate those folios away, unpin all the folios in the range. If
+ * migration of the entire set of folios succeeds, then -EAGAIN is returned. The
+ * caller should re-pin the entire range with FOLL_PIN and then call this
+ * routine again.
+ *
+ * -ENOMEM, or any other -errno: if an error *other* than -EAGAIN occurs, this
+ * indicates a migration failure. The caller should give up, and propagate the
+ * error back up the call stack. The caller does not need to unpin any folios in
+ * that case, because this routine will do the unpinning.
*/
static long check_and_migrate_movable_folios(unsigned long nr_folios,
struct folio **folios)
@@ -2425,10 +2430,8 @@ static long check_and_migrate_movable_fo
}
/*
- * This routine just converts all the pages in the @pages array to folios and
- * calls check_and_migrate_movable_folios() to do the heavy lifting.
- *
- * Please see the check_and_migrate_movable_folios() documentation for details.
+ * Return values and behavior are the same as those for
+ * check_and_migrate_movable_folios().
*/
static long check_and_migrate_movable_pages(unsigned long nr_pages,
struct page **pages)
@@ -2437,8 +2440,10 @@ static long check_and_migrate_movable_pa
long i, ret;
folios = kmalloc_array(nr_pages, sizeof(*folios), GFP_KERNEL);
- if (!folios)
+ if (!folios) {
+ unpin_user_pages(pages, nr_pages);
return -ENOMEM;
+ }
for (i = 0; i < nr_pages; i++)
folios[i] = page_folio(pages[i]);
_
Patches currently in -mm which might be from jhubbard@xxxxxxxxxx are
mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions.patch
mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions-v3.patch
mm-gup-memfd-stop-leaking-pinned-pages-in-low-memory-conditions.patch
kaslr-rename-physmem_end-and-physmem_end-to-direct_map_physmem_end.patch
