| Message ID | 20190121151702.28863-1-hch@lst.de (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | iomap: get/put the page in iomap_page_create/release() | expand |
On Mon, Jan 21, 2019 at 04:17:02PM +0100, Christoph Hellwig wrote: > From: Piotr Jaroszynski <pjaroszynski@nvidia.com> > > 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. > > Fixes: 82cb14175e7d ("xfs: add support for sub-pagesize writeback without buffer_heads") > Signed-off-by: Piotr Jaroszynski <pjaroszynski@nvidia.com> > [hch: actually get/put the page iomap_migrate_page() to make it work > properly] > Signed-off-by: Christoph Hellwig <hch@lst.de> Looks ok (apparently I forgot to ack this explicitly...) Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> --D > --- > fs/iomap.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/fs/iomap.c b/fs/iomap.c > index 987fefc054b4..47362397cb82 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); > SetPagePrivate(page); > return iop; > @@ -132,6 +138,7 @@ 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); > } > > @@ -569,8 +576,10 @@ iomap_migrate_page(struct address_space *mapping, struct page *newpage, > > if (page_has_private(page)) { > ClearPagePrivate(page); > + get_page(newpage); > set_page_private(newpage, page_private(page)); > set_page_private(page, 0); > + put_page(page); > SetPagePrivate(newpage); > } > > -- > 2.20.1 >
diff --git a/fs/iomap.c b/fs/iomap.c index 987fefc054b4..47362397cb82 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); SetPagePrivate(page); return iop; @@ -132,6 +138,7 @@ 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); } @@ -569,8 +576,10 @@ iomap_migrate_page(struct address_space *mapping, struct page *newpage, if (page_has_private(page)) { ClearPagePrivate(page); + get_page(newpage); set_page_private(newpage, page_private(page)); set_page_private(page, 0); + put_page(page); SetPagePrivate(newpage); }