[PATCH v3 5/6] dax: move writeback calls into the filesystems

Ross Zwisler
2016-02-17T03:34:43Z

Previously calls to dax_writeback_mapping_range() for all DAX filesystems
(ext2, ext4 & xfs) were centralized in filemap_write_and_wait_range().
dax_writeback_mapping_range() needs a struct block_device, and it used to
get that from inode->i_sb->s_bdev. This is correct for normal inodes
mounted on ext2, ext4 and XFS filesystems, but is incorrect for DAX raw
block devices and for XFS real-time files.

Instead, call dax_writeback_mapping_range() directly from the filesystem
->writepages function so that it can supply us with a valid block
device. This also fixes DAX code to properly flush caches in response to
sync(2).

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/block_dev.c | 13 ++++++++++++-
fs/dax.c | 12 +++++++-----
fs/ext2/inode.c | 8 ++++++++
fs/ext4/inode.c | 4 ++++
fs/xfs/xfs_aops.c | 4 ++++
include/linux/dax.h | 6 ++++--
mm/filemap.c | 12 ++++--------
7 files changed, 43 insertions(+), 16 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 31c6d10..826b164 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1697,13 +1697,24 @@ static int blkdev_releasepage(struct page *page, gfp_t wait)
return try_to_free_buffers(page);
}

+static int blkdev_writepages(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ if (dax_mapping(mapping)) {
+ struct block_device *bdev = I_BDEV(mapping->host);
+
+ return dax_writeback_mapping_range(mapping, bdev, wbc);
+ }
+ return generic_writepages(mapping, wbc);
+}
+
static const struct address_space_operations def_blk_aops = {
.readpage = blkdev_readpage,
.readpages = blkdev_readpages,
.writepage = blkdev_writepage,
.write_begin = blkdev_write_begin,
.write_end = blkdev_write_end,
- .writepages = generic_writepages,
+ .writepages = blkdev_writepages,
.releasepage = blkdev_releasepage,
.direct_IO = blkdev_direct_IO,
.is_dirty_writeback = buffer_check_dirty_writeback,
diff --git a/fs/dax.c b/fs/dax.c
index 9a173dd..7111724 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -484,11 +484,10 @@ static int dax_writeback_one(struct block_device *bdev,
* end]. This is required by data integrity operations to ensure file data is
* on persistent storage prior to completion of the operation.
*/
-int dax_writeback_mapping_range(struct address_space *mapping, loff_t start,
- loff_t end)
+int dax_writeback_mapping_range(struct address_space *mapping,
+ struct block_device *bdev, struct writeback_control *wbc)
{
struct inode *inode = mapping->host;
- struct block_device *bdev = inode->i_sb->s_bdev;
pgoff_t start_index, end_index, pmd_index;
pgoff_t indices[PAGEVEC_SIZE];
struct pagevec pvec;
@@ -499,8 +498,11 @@ int dax_writeback_mapping_range(struct address_space *mapping, loff_t start,
if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
return -EIO;

- start_index = start >> PAGE_CACHE_SHIFT;
- end_index = end >> PAGE_CACHE_SHIFT;
+ if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
+ return 0;
+
+ start_index = wbc->range_start >> PAGE_CACHE_SHIFT;
+ end_index = wbc->range_end >> PAGE_CACHE_SHIFT;
pmd_index = DAX_PMD_INDEX(start_index);

rcu_read_lock();
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 4467cbd..6bd58e6 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -876,6 +876,14 @@ ext2_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset)
static int
ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
+#ifdef CONFIG_FS_DAX
+ if (dax_mapping(mapping)) {
+ return dax_writeback_mapping_range(mapping,
+ mapping->host->i_sb->s_bdev,
+ wbc);
+ }
+#endif
+
return mpage_writepages(mapping, wbc, ext2_get_block);
}

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7088aa5..c2d1b51 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2450,6 +2450,10 @@ static int ext4_writepages(struct address_space *mapping,

trace_ext4_writepages(inode, wbc);

+ if (dax_mapping(mapping))
+ return dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev,
+ wbc);
+
/*
* No pages to write? This is mainly a kludge to avoid starting
* a transaction for special inodes like journal inode on last iput()
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index fc20518..a9ebabfe 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1208,6 +1208,10 @@ xfs_vm_writepages(
struct writeback_control *wbc)
{
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);
+
return generic_writepages(mapping, wbc);
}

diff --git a/include/linux/dax.h b/include/linux/dax.h
index 7b6bced..636dd59 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -52,6 +52,8 @@ static inline bool dax_mapping(struct address_space *mapping)
{
return mapping->host && IS_DAX(mapping->host);
}
-int dax_writeback_mapping_range(struct address_space *mapping, loff_t start,
- loff_t end);
+
+struct writeback_control;
+int dax_writeback_mapping_range(struct address_space *mapping,
+ struct block_device *bdev, struct writeback_control *wbc);
#endif
diff --git a/mm/filemap.c b/mm/filemap.c
index 23edcce..3461d97 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -446,7 +446,8 @@ int filemap_write_and_wait(struct address_space *mapping)
{
int err = 0;

- if (mapping->nrpages) {
+ if ((!dax_mapping(mapping) && mapping->nrpages) ||
+ (dax_mapping(mapping) && mapping->nrexceptional)) {
err = filemap_fdatawrite(mapping);
/*
* Even if the above returned error, the pages may be
@@ -482,13 +483,8 @@ int filemap_write_and_wait_range(struct address_space *mapping,
{
int err = 0;

- if (dax_mapping(mapping) && mapping->nrexceptional) {
- err = dax_writeback_mapping_range(mapping, lstart, lend);
- if (err)
- return err;
- }
-
- if (mapping->nrpages) {
+ if ((!dax_mapping(mapping) && mapping->nrpages) ||
+ (dax_mapping(mapping) && mapping->nrexceptional)) {
err = __filemap_fdatawrite_range(mapping, lstart, lend,
WB_SYNC_ALL);
/* See comment of filemap_write_and_wait() */
--
2.5.0