From: Piotr Jaroszynski <pjaroszynski@xxxxxxxxxx>
migrate_page_move_mapping() expects pages with private data set to have
a page_count elevated by 1. This is what used to happen for xfs through
the buffer_heads code before the switch to iomap in 82cb14175e7d ("xfs:
add support for sub-pagesize writeback without buffer_heads"). Not
having the count elevated causes move_pages() to fail on memory mapped
files coming from xfs.
Make iomap compatible with the migrate_page_move_mapping() assumption
by elevating the page count as part of iomap_page_create() and lowering
it in iomap_page_release().
Fixes: 82cb14175e7d ("xfs: add support for sub-pagesize writeback
without buffer_heads")
Signed-off-by: Piotr Jaroszynski <pjaroszynski@xxxxxxxxxx>
---
fs/iomap.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/iomap.c b/fs/iomap.c
index 90c2febc93ac..23977f9f23a2 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -117,6 +117,12 @@ iomap_page_create(struct inode *inode, struct page *page)
atomic_set(&iop->read_count, 0);
atomic_set(&iop->write_count, 0);
bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);
+
+ /*
+ * At least migrate_page_move_mapping() assumes that pages with private
+ * data have their count elevated by 1.
+ */
+ get_page(page);
set_page_private(page, (unsigned long)iop);
SetPagePrivate(page);
return iop;
@@ -133,6 +139,7 @@ iomap_page_release(struct page *page)
WARN_ON_ONCE(atomic_read(&iop->write_count));
ClearPagePrivate(page);
set_page_private(page, 0);
+ put_page(page);
kfree(iop);
}
--
2.11.0.262.g4b0a5b2.dirty
