[02/19] dax: Pass dax_dev to dax_writeback_mapping_range()
diff mbox series

Message ID 20190821175720.25901-3-vgoyal@redhat.com
State New
Headers show
Series
  • virtio-fs: Enable DAX support
Related show

Commit Message

Vivek Goyal Aug. 21, 2019, 5:57 p.m. UTC
Right now dax_writeback_mapping_range() is passed a bdev and dax_dev
is searched from that bdev name.

virtio-fs does not have a bdev. So pass in dax_dev also to
dax_writeback_mapping_range(). If dax_dev is passed in, bdev is not
used otherwise dax_dev is searched using bdev.

Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/dax.c            | 16 ++++++++++------
 fs/ext2/inode.c     |  2 +-
 fs/ext4/inode.c     |  2 +-
 fs/xfs/xfs_aops.c   |  2 +-
 include/linux/dax.h |  6 ++++--
 5 files changed, 17 insertions(+), 11 deletions(-)

Comments

Christoph Hellwig Aug. 26, 2019, 11:53 a.m. UTC | #1
On Wed, Aug 21, 2019 at 01:57:03PM -0400, Vivek Goyal wrote:
> Right now dax_writeback_mapping_range() is passed a bdev and dax_dev
> is searched from that bdev name.
> 
> virtio-fs does not have a bdev. So pass in dax_dev also to
> dax_writeback_mapping_range(). If dax_dev is passed in, bdev is not
> used otherwise dax_dev is searched using bdev.

Please just pass in only the dax_device and get rid of the block device.
The callers should have one at hand easily, e.g. for XFS just call
xfs_find_daxdev_for_inode instead of xfs_find_bdev_for_inode.
Vivek Goyal Aug. 26, 2019, 8:33 p.m. UTC | #2
On Mon, Aug 26, 2019 at 04:53:16AM -0700, Christoph Hellwig wrote:
> On Wed, Aug 21, 2019 at 01:57:03PM -0400, Vivek Goyal wrote:
> > Right now dax_writeback_mapping_range() is passed a bdev and dax_dev
> > is searched from that bdev name.
> > 
> > virtio-fs does not have a bdev. So pass in dax_dev also to
> > dax_writeback_mapping_range(). If dax_dev is passed in, bdev is not
> > used otherwise dax_dev is searched using bdev.
> 
> Please just pass in only the dax_device and get rid of the block device.
> The callers should have one at hand easily, e.g. for XFS just call
> xfs_find_daxdev_for_inode instead of xfs_find_bdev_for_inode.

Sure. Here is the updated patch.

This patch can probably go upstream independently. If you are fine with
the patch, I can post it separately for inclusion.


Subject: dax: Pass dax_dev instead of bdev to dax_writeback_mapping_range()

As of now dax_writeback_mapping_range() takes "struct block_device" as a
parameter and dax_dev is searched from bdev name. This also involves taking
a fresh reference on dax_dev and putting that reference at the end of
function.

We are developing a new filesystem virtio-fs and using dax to access host
page cache directly. But there is no block device. IOW, we want to make
use of dax but want to get rid of this assumption that there is always
a block device associated with dax_dev.

So pass in "struct dax_device" as parameter instead of bdev.

ext2/ext4/xfs are current users and they already have a reference on
dax_device. So there is no need to take reference and drop reference to
dax_device on each call of this function.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/dax.c            |    8 +-------
 fs/ext2/inode.c     |    5 +++--
 fs/ext4/inode.c     |    2 +-
 fs/xfs/xfs_aops.c   |    2 +-
 include/linux/dax.h |    2 +-
 5 files changed, 7 insertions(+), 12 deletions(-)

Index: rhvgoyal-linux-fuse/fs/dax.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/dax.c	2019-08-26 11:20:36.545009968 -0400
+++ rhvgoyal-linux-fuse/fs/dax.c	2019-08-26 11:24:43.973009968 -0400
@@ -936,12 +936,11 @@ static int dax_writeback_one(struct xa_s
  * on persistent storage prior to completion of the operation.
  */
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc)
+		struct dax_device *dax_dev, struct writeback_control *wbc)
 {
 	XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
 	struct inode *inode = mapping->host;
 	pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
-	struct dax_device *dax_dev;
 	void *entry;
 	int ret = 0;
 	unsigned int scanned = 0;
@@ -952,10 +951,6 @@ int dax_writeback_mapping_range(struct a
 	if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 		return 0;
 
-	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
-	if (!dax_dev)
-		return -EIO;
-
 	trace_dax_writeback_range(inode, xas.xa_index, end_index);
 
 	tag_pages_for_writeback(mapping, xas.xa_index, end_index);
@@ -976,7 +971,6 @@ int dax_writeback_mapping_range(struct a
 		xas_lock_irq(&xas);
 	}
 	xas_unlock_irq(&xas);
-	put_dax(dax_dev);
 	trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
 	return ret;
 }
Index: rhvgoyal-linux-fuse/include/linux/dax.h
===================================================================
--- rhvgoyal-linux-fuse.orig/include/linux/dax.h	2019-08-26 11:20:36.545009968 -0400
+++ rhvgoyal-linux-fuse/include/linux/dax.h	2019-08-26 11:26:08.384009968 -0400
@@ -141,7 +141,7 @@ static inline void fs_put_dax(struct dax
 
 struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc);
+		struct dax_device *dax_dev, struct writeback_control *wbc);
 
 struct page *dax_layout_busy_page(struct address_space *mapping);
 dax_entry_t dax_lock_page(struct page *page);
Index: rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/xfs/xfs_aops.c	2019-08-26 11:20:36.545009968 -0400
+++ rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c	2019-08-26 11:34:51.085009968 -0400
@@ -1120,7 +1120,7 @@ xfs_dax_writepages(
 {
 	xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
 	return dax_writeback_mapping_range(mapping,
-			xfs_find_bdev_for_inode(mapping->host), wbc);
+			xfs_find_daxdev_for_inode(mapping->host), wbc);
 }
 
 STATIC int
Index: rhvgoyal-linux-fuse/fs/ext4/inode.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/ext4/inode.c	2019-08-26 11:20:36.545009968 -0400
+++ rhvgoyal-linux-fuse/fs/ext4/inode.c	2019-08-26 11:39:56.828009968 -0400
@@ -2992,7 +2992,7 @@ static int ext4_dax_writepages(struct ad
 	percpu_down_read(&sbi->s_journal_flag_rwsem);
 	trace_ext4_writepages(inode, wbc);
 
-	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, wbc);
+	ret = dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
 	trace_ext4_writepages_result(inode, wbc, ret,
 				     nr_to_write - wbc->nr_to_write);
 	percpu_up_read(&sbi->s_journal_flag_rwsem);
Index: rhvgoyal-linux-fuse/fs/ext2/inode.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/ext2/inode.c	2019-08-26 11:20:36.545009968 -0400
+++ rhvgoyal-linux-fuse/fs/ext2/inode.c	2019-08-26 11:43:04.842009968 -0400
@@ -957,8 +957,9 @@ ext2_writepages(struct address_space *ma
 static int
 ext2_dax_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
-	return dax_writeback_mapping_range(mapping,
-			mapping->host->i_sb->s_bdev, wbc);
+	struct ext2_sb_info *sbi = EXT2_SB(mapping->host->i_sb);
+
+	return dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
 }
 
 const struct address_space_operations ext2_aops = {
Vivek Goyal Aug. 26, 2019, 8:58 p.m. UTC | #3
On Mon, Aug 26, 2019 at 04:33:26PM -0400, Vivek Goyal wrote:
> On Mon, Aug 26, 2019 at 04:53:16AM -0700, Christoph Hellwig wrote:
> > On Wed, Aug 21, 2019 at 01:57:03PM -0400, Vivek Goyal wrote:
> > > Right now dax_writeback_mapping_range() is passed a bdev and dax_dev
> > > is searched from that bdev name.
> > > 
> > > virtio-fs does not have a bdev. So pass in dax_dev also to
> > > dax_writeback_mapping_range(). If dax_dev is passed in, bdev is not
> > > used otherwise dax_dev is searched using bdev.
> > 
> > Please just pass in only the dax_device and get rid of the block device.
> > The callers should have one at hand easily, e.g. for XFS just call
> > xfs_find_daxdev_for_inode instead of xfs_find_bdev_for_inode.
> 
> Sure. Here is the updated patch.
> 
> This patch can probably go upstream independently. If you are fine with
> the patch, I can post it separately for inclusion.

Forgot to update function declaration in case of !CONFIG_FS_DAX. Here is
the updated patch.

Subject: dax: Pass dax_dev instead of bdev to dax_writeback_mapping_range()

As of now dax_writeback_mapping_range() takes "struct block_device" as a
parameter and dax_dev is searched from bdev name. This also involves taking
a fresh reference on dax_dev and putting that reference at the end of
function.

We are developing a new filesystem virtio-fs and using dax to access host
page cache directly. But there is no block device. IOW, we want to make
use of dax but want to get rid of this assumption that there is always
a block device associated with dax_dev.

So pass in "struct dax_device" as parameter instead of bdev.

ext2/ext4/xfs are current users and they already have a reference on
dax_device. So there is no need to take reference and drop reference to
dax_device on each call of this function.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/dax.c            |    8 +-------
 fs/ext2/inode.c     |    5 +++--
 fs/ext4/inode.c     |    2 +-
 fs/xfs/xfs_aops.c   |    2 +-
 include/linux/dax.h |    4 ++--
 5 files changed, 8 insertions(+), 13 deletions(-)

Index: rhvgoyal-linux-fuse/fs/dax.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/dax.c	2019-08-26 16:45:26.093710196 -0400
+++ rhvgoyal-linux-fuse/fs/dax.c	2019-08-26 16:45:29.462710196 -0400
@@ -936,12 +936,11 @@ static int dax_writeback_one(struct xa_s
  * on persistent storage prior to completion of the operation.
  */
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc)
+		struct dax_device *dax_dev, struct writeback_control *wbc)
 {
 	XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
 	struct inode *inode = mapping->host;
 	pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
-	struct dax_device *dax_dev;
 	void *entry;
 	int ret = 0;
 	unsigned int scanned = 0;
@@ -952,10 +951,6 @@ int dax_writeback_mapping_range(struct a
 	if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 		return 0;
 
-	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
-	if (!dax_dev)
-		return -EIO;
-
 	trace_dax_writeback_range(inode, xas.xa_index, end_index);
 
 	tag_pages_for_writeback(mapping, xas.xa_index, end_index);
@@ -976,7 +971,6 @@ int dax_writeback_mapping_range(struct a
 		xas_lock_irq(&xas);
 	}
 	xas_unlock_irq(&xas);
-	put_dax(dax_dev);
 	trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
 	return ret;
 }
Index: rhvgoyal-linux-fuse/include/linux/dax.h
===================================================================
--- rhvgoyal-linux-fuse.orig/include/linux/dax.h	2019-08-26 16:45:26.094710196 -0400
+++ rhvgoyal-linux-fuse/include/linux/dax.h	2019-08-26 16:46:08.101710196 -0400
@@ -141,7 +141,7 @@ static inline void fs_put_dax(struct dax
 
 struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc);
+		struct dax_device *dax_dev, struct writeback_control *wbc);
 
 struct page *dax_layout_busy_page(struct address_space *mapping);
 dax_entry_t dax_lock_page(struct page *page);
@@ -180,7 +180,7 @@ static inline struct page *dax_layout_bu
 }
 
 static inline int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc)
+		struct dax_device *dax_dev, struct writeback_control *wbc)
 {
 	return -EOPNOTSUPP;
 }
Index: rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/xfs/xfs_aops.c	2019-08-26 16:45:26.094710196 -0400
+++ rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c	2019-08-26 16:45:29.471710196 -0400
@@ -1120,7 +1120,7 @@ xfs_dax_writepages(
 {
 	xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
 	return dax_writeback_mapping_range(mapping,
-			xfs_find_bdev_for_inode(mapping->host), wbc);
+			xfs_find_daxdev_for_inode(mapping->host), wbc);
 }
 
 STATIC int
Index: rhvgoyal-linux-fuse/fs/ext4/inode.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/ext4/inode.c	2019-08-26 16:45:26.093710196 -0400
+++ rhvgoyal-linux-fuse/fs/ext4/inode.c	2019-08-26 16:45:29.475710196 -0400
@@ -2992,7 +2992,7 @@ static int ext4_dax_writepages(struct ad
 	percpu_down_read(&sbi->s_journal_flag_rwsem);
 	trace_ext4_writepages(inode, wbc);
 
-	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, wbc);
+	ret = dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
 	trace_ext4_writepages_result(inode, wbc, ret,
 				     nr_to_write - wbc->nr_to_write);
 	percpu_up_read(&sbi->s_journal_flag_rwsem);
Index: rhvgoyal-linux-fuse/fs/ext2/inode.c
===================================================================
--- rhvgoyal-linux-fuse.orig/fs/ext2/inode.c	2019-08-26 16:45:26.093710196 -0400
+++ rhvgoyal-linux-fuse/fs/ext2/inode.c	2019-08-26 16:45:29.477710196 -0400
@@ -957,8 +957,9 @@ ext2_writepages(struct address_space *ma
 static int
 ext2_dax_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
-	return dax_writeback_mapping_range(mapping,
-			mapping->host->i_sb->s_bdev, wbc);
+	struct ext2_sb_info *sbi = EXT2_SB(mapping->host->i_sb);
+
+	return dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
 }
 
 const struct address_space_operations ext2_aops = {
Dan Williams Aug. 26, 2019, 9:33 p.m. UTC | #4
[ add Jan ]

On Mon, Aug 26, 2019 at 1:58 PM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> On Mon, Aug 26, 2019 at 04:33:26PM -0400, Vivek Goyal wrote:
> > On Mon, Aug 26, 2019 at 04:53:16AM -0700, Christoph Hellwig wrote:
> > > On Wed, Aug 21, 2019 at 01:57:03PM -0400, Vivek Goyal wrote:
> > > > Right now dax_writeback_mapping_range() is passed a bdev and dax_dev
> > > > is searched from that bdev name.
> > > >
> > > > virtio-fs does not have a bdev. So pass in dax_dev also to
> > > > dax_writeback_mapping_range(). If dax_dev is passed in, bdev is not
> > > > used otherwise dax_dev is searched using bdev.
> > >
> > > Please just pass in only the dax_device and get rid of the block device.
> > > The callers should have one at hand easily, e.g. for XFS just call
> > > xfs_find_daxdev_for_inode instead of xfs_find_bdev_for_inode.
> >
> > Sure. Here is the updated patch.
> >
> > This patch can probably go upstream independently. If you are fine with
> > the patch, I can post it separately for inclusion.
>
> Forgot to update function declaration in case of !CONFIG_FS_DAX. Here is
> the updated patch.
>
> Subject: dax: Pass dax_dev instead of bdev to dax_writeback_mapping_range()
>
> As of now dax_writeback_mapping_range() takes "struct block_device" as a
> parameter and dax_dev is searched from bdev name. This also involves taking
> a fresh reference on dax_dev and putting that reference at the end of
> function.
>
> We are developing a new filesystem virtio-fs and using dax to access host
> page cache directly. But there is no block device. IOW, we want to make
> use of dax but want to get rid of this assumption that there is always
> a block device associated with dax_dev.
>
> So pass in "struct dax_device" as parameter instead of bdev.
>
> ext2/ext4/xfs are current users and they already have a reference on
> dax_device. So there is no need to take reference and drop reference to
> dax_device on each call of this function.
>
> Suggested-by: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
>  fs/dax.c            |    8 +-------
>  fs/ext2/inode.c     |    5 +++--
>  fs/ext4/inode.c     |    2 +-
>  fs/xfs/xfs_aops.c   |    2 +-
>  include/linux/dax.h |    4 ++--

Looks good to me. Would be nice to get some ext4 and xfs acks then
I'll take it through the dax tree for v5.4.

>  5 files changed, 8 insertions(+), 13 deletions(-)
>
> Index: rhvgoyal-linux-fuse/fs/dax.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/dax.c   2019-08-26 16:45:26.093710196 -0400
> +++ rhvgoyal-linux-fuse/fs/dax.c        2019-08-26 16:45:29.462710196 -0400
> @@ -936,12 +936,11 @@ static int dax_writeback_one(struct xa_s
>   * on persistent storage prior to completion of the operation.
>   */
>  int dax_writeback_mapping_range(struct address_space *mapping,
> -               struct block_device *bdev, struct writeback_control *wbc)
> +               struct dax_device *dax_dev, struct writeback_control *wbc)
>  {
>         XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
>         struct inode *inode = mapping->host;
>         pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
> -       struct dax_device *dax_dev;
>         void *entry;
>         int ret = 0;
>         unsigned int scanned = 0;
> @@ -952,10 +951,6 @@ int dax_writeback_mapping_range(struct a
>         if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
>                 return 0;
>
> -       dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
> -       if (!dax_dev)
> -               return -EIO;
> -
>         trace_dax_writeback_range(inode, xas.xa_index, end_index);
>
>         tag_pages_for_writeback(mapping, xas.xa_index, end_index);
> @@ -976,7 +971,6 @@ int dax_writeback_mapping_range(struct a
>                 xas_lock_irq(&xas);
>         }
>         xas_unlock_irq(&xas);
> -       put_dax(dax_dev);
>         trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
>         return ret;
>  }
> Index: rhvgoyal-linux-fuse/include/linux/dax.h
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/include/linux/dax.h        2019-08-26 16:45:26.094710196 -0400
> +++ rhvgoyal-linux-fuse/include/linux/dax.h     2019-08-26 16:46:08.101710196 -0400
> @@ -141,7 +141,7 @@ static inline void fs_put_dax(struct dax
>
>  struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
>  int dax_writeback_mapping_range(struct address_space *mapping,
> -               struct block_device *bdev, struct writeback_control *wbc);
> +               struct dax_device *dax_dev, struct writeback_control *wbc);
>
>  struct page *dax_layout_busy_page(struct address_space *mapping);
>  dax_entry_t dax_lock_page(struct page *page);
> @@ -180,7 +180,7 @@ static inline struct page *dax_layout_bu
>  }
>
>  static inline int dax_writeback_mapping_range(struct address_space *mapping,
> -               struct block_device *bdev, struct writeback_control *wbc)
> +               struct dax_device *dax_dev, struct writeback_control *wbc)
>  {
>         return -EOPNOTSUPP;
>  }
> Index: rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/xfs/xfs_aops.c  2019-08-26 16:45:26.094710196 -0400
> +++ rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c       2019-08-26 16:45:29.471710196 -0400
> @@ -1120,7 +1120,7 @@ xfs_dax_writepages(
>  {
>         xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
>         return dax_writeback_mapping_range(mapping,
> -                       xfs_find_bdev_for_inode(mapping->host), wbc);
> +                       xfs_find_daxdev_for_inode(mapping->host), wbc);
>  }
>
>  STATIC int
> Index: rhvgoyal-linux-fuse/fs/ext4/inode.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/ext4/inode.c    2019-08-26 16:45:26.093710196 -0400
> +++ rhvgoyal-linux-fuse/fs/ext4/inode.c 2019-08-26 16:45:29.475710196 -0400
> @@ -2992,7 +2992,7 @@ static int ext4_dax_writepages(struct ad
>         percpu_down_read(&sbi->s_journal_flag_rwsem);
>         trace_ext4_writepages(inode, wbc);
>
> -       ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, wbc);
> +       ret = dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
>         trace_ext4_writepages_result(inode, wbc, ret,
>                                      nr_to_write - wbc->nr_to_write);
>         percpu_up_read(&sbi->s_journal_flag_rwsem);
> Index: rhvgoyal-linux-fuse/fs/ext2/inode.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/ext2/inode.c    2019-08-26 16:45:26.093710196 -0400
> +++ rhvgoyal-linux-fuse/fs/ext2/inode.c 2019-08-26 16:45:29.477710196 -0400
> @@ -957,8 +957,9 @@ ext2_writepages(struct address_space *ma
>  static int
>  ext2_dax_writepages(struct address_space *mapping, struct writeback_control *wbc)
>  {
> -       return dax_writeback_mapping_range(mapping,
> -                       mapping->host->i_sb->s_bdev, wbc);
> +       struct ext2_sb_info *sbi = EXT2_SB(mapping->host->i_sb);
> +
> +       return dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
>  }
>
>  const struct address_space_operations ext2_aops = {
Jan Kara Aug. 27, 2019, 1:45 p.m. UTC | #5
On Mon 26-08-19 16:33:26, Vivek Goyal wrote:
> On Mon, Aug 26, 2019 at 04:53:16AM -0700, Christoph Hellwig wrote:
> > On Wed, Aug 21, 2019 at 01:57:03PM -0400, Vivek Goyal wrote:
> > > Right now dax_writeback_mapping_range() is passed a bdev and dax_dev
> > > is searched from that bdev name.
> > > 
> > > virtio-fs does not have a bdev. So pass in dax_dev also to
> > > dax_writeback_mapping_range(). If dax_dev is passed in, bdev is not
> > > used otherwise dax_dev is searched using bdev.
> > 
> > Please just pass in only the dax_device and get rid of the block device.
> > The callers should have one at hand easily, e.g. for XFS just call
> > xfs_find_daxdev_for_inode instead of xfs_find_bdev_for_inode.
> 
> Sure. Here is the updated patch.
> 
> This patch can probably go upstream independently. If you are fine with
> the patch, I can post it separately for inclusion.
> 
> 
> Subject: dax: Pass dax_dev instead of bdev to dax_writeback_mapping_range()
> 
> As of now dax_writeback_mapping_range() takes "struct block_device" as a
> parameter and dax_dev is searched from bdev name. This also involves taking
> a fresh reference on dax_dev and putting that reference at the end of
> function.
> 
> We are developing a new filesystem virtio-fs and using dax to access host
> page cache directly. But there is no block device. IOW, we want to make
> use of dax but want to get rid of this assumption that there is always
> a block device associated with dax_dev.
> 
> So pass in "struct dax_device" as parameter instead of bdev.
> 
> ext2/ext4/xfs are current users and they already have a reference on
> dax_device. So there is no need to take reference and drop reference to
> dax_device on each call of this function.
> 
> Suggested-by: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Looks good to me. You can add:

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

								Honza
> ---
>  fs/dax.c            |    8 +-------
>  fs/ext2/inode.c     |    5 +++--
>  fs/ext4/inode.c     |    2 +-
>  fs/xfs/xfs_aops.c   |    2 +-
>  include/linux/dax.h |    2 +-
>  5 files changed, 7 insertions(+), 12 deletions(-)
> 
> Index: rhvgoyal-linux-fuse/fs/dax.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/dax.c	2019-08-26 11:20:36.545009968 -0400
> +++ rhvgoyal-linux-fuse/fs/dax.c	2019-08-26 11:24:43.973009968 -0400
> @@ -936,12 +936,11 @@ static int dax_writeback_one(struct xa_s
>   * on persistent storage prior to completion of the operation.
>   */
>  int dax_writeback_mapping_range(struct address_space *mapping,
> -		struct block_device *bdev, struct writeback_control *wbc)
> +		struct dax_device *dax_dev, struct writeback_control *wbc)
>  {
>  	XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
>  	struct inode *inode = mapping->host;
>  	pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
> -	struct dax_device *dax_dev;
>  	void *entry;
>  	int ret = 0;
>  	unsigned int scanned = 0;
> @@ -952,10 +951,6 @@ int dax_writeback_mapping_range(struct a
>  	if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
>  		return 0;
>  
> -	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
> -	if (!dax_dev)
> -		return -EIO;
> -
>  	trace_dax_writeback_range(inode, xas.xa_index, end_index);
>  
>  	tag_pages_for_writeback(mapping, xas.xa_index, end_index);
> @@ -976,7 +971,6 @@ int dax_writeback_mapping_range(struct a
>  		xas_lock_irq(&xas);
>  	}
>  	xas_unlock_irq(&xas);
> -	put_dax(dax_dev);
>  	trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
>  	return ret;
>  }
> Index: rhvgoyal-linux-fuse/include/linux/dax.h
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/include/linux/dax.h	2019-08-26 11:20:36.545009968 -0400
> +++ rhvgoyal-linux-fuse/include/linux/dax.h	2019-08-26 11:26:08.384009968 -0400
> @@ -141,7 +141,7 @@ static inline void fs_put_dax(struct dax
>  
>  struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
>  int dax_writeback_mapping_range(struct address_space *mapping,
> -		struct block_device *bdev, struct writeback_control *wbc);
> +		struct dax_device *dax_dev, struct writeback_control *wbc);
>  
>  struct page *dax_layout_busy_page(struct address_space *mapping);
>  dax_entry_t dax_lock_page(struct page *page);
> Index: rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/xfs/xfs_aops.c	2019-08-26 11:20:36.545009968 -0400
> +++ rhvgoyal-linux-fuse/fs/xfs/xfs_aops.c	2019-08-26 11:34:51.085009968 -0400
> @@ -1120,7 +1120,7 @@ xfs_dax_writepages(
>  {
>  	xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
>  	return dax_writeback_mapping_range(mapping,
> -			xfs_find_bdev_for_inode(mapping->host), wbc);
> +			xfs_find_daxdev_for_inode(mapping->host), wbc);
>  }
>  
>  STATIC int
> Index: rhvgoyal-linux-fuse/fs/ext4/inode.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/ext4/inode.c	2019-08-26 11:20:36.545009968 -0400
> +++ rhvgoyal-linux-fuse/fs/ext4/inode.c	2019-08-26 11:39:56.828009968 -0400
> @@ -2992,7 +2992,7 @@ static int ext4_dax_writepages(struct ad
>  	percpu_down_read(&sbi->s_journal_flag_rwsem);
>  	trace_ext4_writepages(inode, wbc);
>  
> -	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, wbc);
> +	ret = dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
>  	trace_ext4_writepages_result(inode, wbc, ret,
>  				     nr_to_write - wbc->nr_to_write);
>  	percpu_up_read(&sbi->s_journal_flag_rwsem);
> Index: rhvgoyal-linux-fuse/fs/ext2/inode.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/fs/ext2/inode.c	2019-08-26 11:20:36.545009968 -0400
> +++ rhvgoyal-linux-fuse/fs/ext2/inode.c	2019-08-26 11:43:04.842009968 -0400
> @@ -957,8 +957,9 @@ ext2_writepages(struct address_space *ma
>  static int
>  ext2_dax_writepages(struct address_space *mapping, struct writeback_control *wbc)
>  {
> -	return dax_writeback_mapping_range(mapping,
> -			mapping->host->i_sb->s_bdev, wbc);
> +	struct ext2_sb_info *sbi = EXT2_SB(mapping->host->i_sb);
> +
> +	return dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
>  }
>  
>  const struct address_space_operations ext2_aops = {
Christoph Hellwig Aug. 28, 2019, 6:58 a.m. UTC | #6
Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Patch
diff mbox series

diff --git a/fs/dax.c b/fs/dax.c
index a11147bbaf9e..60620a37030c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -936,12 +936,12 @@  static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
  * on persistent storage prior to completion of the operation.
  */
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc)
+		struct block_device *bdev, struct dax_device *dax_dev,
+		struct writeback_control *wbc)
 {
 	XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
 	struct inode *inode = mapping->host;
 	pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
-	struct dax_device *dax_dev;
 	void *entry;
 	int ret = 0;
 	unsigned int scanned = 0;
@@ -952,9 +952,12 @@  int dax_writeback_mapping_range(struct address_space *mapping,
 	if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 		return 0;
 
-	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
-	if (!dax_dev)
-		return -EIO;
+	if (bdev) {
+		WARN_ON(dax_dev);
+		dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+		if (!dax_dev)
+			return -EIO;
+	}
 
 	trace_dax_writeback_range(inode, xas.xa_index, end_index);
 
@@ -976,7 +979,8 @@  int dax_writeback_mapping_range(struct address_space *mapping,
 		xas_lock_irq(&xas);
 	}
 	xas_unlock_irq(&xas);
-	put_dax(dax_dev);
+	if (bdev)
+		put_dax(dax_dev);
 	trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
 	return ret;
 }
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 7004ce581a32..4e3870c4e255 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -958,7 +958,7 @@  static int
 ext2_dax_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
 	return dax_writeback_mapping_range(mapping,
-			mapping->host->i_sb->s_bdev, wbc);
+			mapping->host->i_sb->s_bdev, NULL, wbc);
 }
 
 const struct address_space_operations ext2_aops = {
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 420fe3deed39..75b85c56c732 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2992,7 +2992,7 @@  static int ext4_dax_writepages(struct address_space *mapping,
 	percpu_down_read(&sbi->s_journal_flag_rwsem);
 	trace_ext4_writepages(inode, wbc);
 
-	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, wbc);
+	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, NULL, wbc);
 	trace_ext4_writepages_result(inode, wbc, ret,
 				     nr_to_write - wbc->nr_to_write);
 	percpu_up_read(&sbi->s_journal_flag_rwsem);
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index f16d5f196c6b..71a7007509c4 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1120,7 +1120,7 @@  xfs_dax_writepages(
 {
 	xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
 	return dax_writeback_mapping_range(mapping,
-			xfs_find_bdev_for_inode(mapping->host), wbc);
+			xfs_find_bdev_for_inode(mapping->host), NULL, wbc);
 }
 
 STATIC int
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 9bd8528bd305..e7f40108f2c9 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -141,7 +141,8 @@  static inline void fs_put_dax(struct dax_device *dax_dev)
 
 struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc);
+		struct block_device *bdev, struct dax_device *dax_dev,
+		struct writeback_control *wbc);
 
 struct page *dax_layout_busy_page(struct address_space *mapping);
 dax_entry_t dax_lock_page(struct page *page);
@@ -180,7 +181,8 @@  static inline struct page *dax_layout_busy_page(struct address_space *mapping)
 }
 
 static inline int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc)
+		struct block_device *bdev, struct dax_device *dax_dev,
+		struct writeback_control *wbc)
 {
 	return -EOPNOTSUPP;
 }