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Subject[PATCH v6 04/15] xfs, dax: introduce xfs_dax_aops
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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: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
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))
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