Re: [PATCH v7 04/14] xfs, dax: introduce xfs_dax_aops

Jan Kara
2018-03-29T15:30:54Z

On Wed 21-03-18 15:57:32, Dan Williams wrote:
> In preparation for the dax implementation to start associating dax pages
> to inodes via page->mapping, we need to provide a 'struct
> address_space_operations' instance for dax. Otherwise, direct-I/O
> triggers incorrect page cache assumptions and warnings like the
> following:
>
> WARNING: CPU: 27 PID: 1783 at fs/xfs/xfs_aops.c:1468
> xfs_vm_set_page_dirty+0xf3/0x1b0 [xfs]
> [..]
> CPU: 27 PID: 1783 Comm: dma-collision Tainted: G O 4.15.0-rc2+ #984
> [..]
> Call Trace:
> set_page_dirty_lock+0x40/0x60
> bio_set_pages_dirty+0x37/0x50
> iomap_dio_actor+0x2b7/0x3b0
> ? iomap_dio_zero+0x110/0x110
> iomap_apply+0xa4/0x110
> iomap_dio_rw+0x29e/0x3b0
> ? iomap_dio_zero+0x110/0x110
> ? xfs_file_dio_aio_read+0x7c/0x1a0 [xfs]
> xfs_file_dio_aio_read+0x7c/0x1a0 [xfs]
> xfs_file_read_iter+0xa0/0xc0 [xfs]
> __vfs_read+0xf9/0x170
> vfs_read+0xa6/0x150
> SyS_pread64+0x93/0xb0
> entry_SYSCALL_64_fastpath+0x1f/0x96
>
> ...where the default set_page_dirty() handler assumes that dirty state
> is being tracked in 'struct page' flags.
>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Matthew Wilcox <mawilcox@microsoft.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Suggested-by: Jan Kara <jack@suse.cz>
> Suggested-by: Dave Chinner <david@fromorbit.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/xfs/xfs_aops.c | 21 +++++++++++++++++----
> fs/xfs/xfs_aops.h | 1 +
> fs/xfs/xfs_iops.c | 5 ++++-
> 3 files changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 9c6a830da0ee..5f1f5948ecc2 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1194,16 +1194,22 @@ xfs_vm_writepages(
> int ret;
>
> xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
> - if (dax_mapping(mapping))
> - return dax_writeback_mapping_range(mapping,
> - xfs_find_bdev_for_inode(mapping->host), wbc);
> -
> ret = write_cache_pages(mapping, wbc, xfs_do_writepage, &wpc);
> if (wpc.ioend)
> ret = xfs_submit_ioend(wbc, wpc.ioend, ret);
> return ret;
> }
>
> +STATIC int
> +xfs_dax_writepages(
> + struct address_space *mapping,
> + struct writeback_control *wbc)
> +{
> + xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
> + return dax_writeback_mapping_range(mapping,
> + xfs_find_bdev_for_inode(mapping->host), wbc);
> +}
> +
> /*
> * Called to move a page into cleanable state - and from there
> * to be released. The page should already be clean. We always
> @@ -1505,3 +1511,10 @@ const struct address_space_operations xfs_address_space_operations = {
> .is_partially_uptodate = block_is_partially_uptodate,
> .error_remove_page = generic_error_remove_page,
> };
> +
> +const struct address_space_operations xfs_dax_aops = {
> + .direct_IO = xfs_vm_direct_IO,
> + .writepages = xfs_dax_writepages,
> + .set_page_dirty = noop_set_page_dirty,
> + .invalidatepage = noop_invalidatepage,
> +};
> diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
> index 88c85ea63da0..69346d460dfa 100644
> --- a/fs/xfs/xfs_aops.h
> +++ b/fs/xfs/xfs_aops.h
> @@ -54,6 +54,7 @@ struct xfs_ioend {
> };
>
> extern const struct address_space_operations xfs_address_space_operations;
> +extern const struct address_space_operations xfs_dax_aops;
>
> int xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
>
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 56475fcd76f2..951e84df5576 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -1272,7 +1272,10 @@ xfs_setup_iops(
> case S_IFREG:
> inode->i_op = &xfs_inode_operations;
> inode->i_fop = &xfs_file_operations;
> - inode->i_mapping->a_ops = &xfs_address_space_operations;
> + if (IS_DAX(inode))
> + inode->i_mapping->a_ops = &xfs_dax_aops;
> + else
> + inode->i_mapping->a_ops = &xfs_address_space_operations;
> break;
> case S_IFDIR:
> if (xfs_sb_version_hasasciici(&XFS_M(inode->i_sb)->m_sb))
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR