diff options
authorPiotr Jaroszynski <pjaroszynski@nvidia.com>2018-12-14 14:17:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-14 15:05:45 -0800
commit61c6de667263184125d5ca75e894fcad632b0dd3 (patch)
parent8ace22bce84014957da37e6b8baa49ee81c03366 (diff)
fs/iomap.c: get/put the page in iomap_page_create/release()
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 commit 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(). It causes the move_pages() syscall to misbehave on memory mapped files from xfs. It does not not move any pages, which I suppose is "just" a perf issue, but it also ends up returning a positive number which is out of spec for the syscall. Talking to Michal Hocko, it sounds like returning positive numbers might be a necessary update to move_pages() anyway though (https://lkml.kernel.org/r/20181116114955.GJ14706@dhcp22.suse.cz). I only hit this in tests that verify that move_pages() actually moved the pages. The test also got confused by the positive return from move_pages() (it got treated as a success as positive numbers were not expected and not handled) making it a bit harder to track down what's going on. Link: http://lkml.kernel.org/r/20181115184140.1388751-1-pjaroszynski@nvidia.com Fixes: 82cb14175e7d ("xfs: add support for sub-pagesize writeback without buffer_heads") Signed-off-by: Piotr Jaroszynski <pjaroszynski@nvidia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: William Kucharski <william.kucharski@oracle.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Brian Foster <bfoster@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/iomap.c b/fs/iomap.c
index d6bc98ae8d35..5bc172f3dfe8 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -116,6 +116,12 @@ 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);
+ /*
+ * 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);
return iop;
@@ -132,6 +138,7 @@ iomap_page_release(struct page *page)
set_page_private(page, 0);
+ put_page(page);