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From: Vivek Goyal <vgoyal@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: miklos@szeredi.hu, linux-nvdimm@lists.01.org,
	linux-kernel@vger.kernel.org, dgilbert@redhat.com,
	virtio-fs@redhat.com, stefanha@redhat.com,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 02/19] dax: Pass dax_dev to dax_writeback_mapping_range()
Date: Mon, 26 Aug 2019 16:58:29 -0400
Message-ID: <20190826205829.GC13860@redhat.com> (raw)
In-Reply-To: <20190826203326.GB13860@redhat.com>

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 = {
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  reply index

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-21 17:57 [PATCH v3 00/19][RFC] virtio-fs: Enable DAX support Vivek Goyal
2019-08-21 17:57 ` [PATCH 01/19] dax: remove block device dependencies Vivek Goyal
2019-08-26 11:51   ` Christoph Hellwig
2019-08-27 16:38     ` Vivek Goyal
2019-08-28  6:58       ` Christoph Hellwig
2019-08-28 17:58         ` Vivek Goyal
2019-08-28 22:53           ` Dave Chinner
2019-08-29  0:04             ` Dan Williams
2019-08-29  9:32               ` Christoph Hellwig
2019-12-16 18:10               ` Vivek Goyal
2020-01-07 12:51                 ` Christoph Hellwig
2020-01-07 14:22                   ` Dan Williams
2020-01-07 17:07                     ` Darrick J. Wong
2020-01-07 17:29                       ` Dan Williams
2020-01-07 18:01                         ` Vivek Goyal
2020-01-07 18:07                           ` Dan Williams
2020-01-07 18:33                             ` Vivek Goyal
2020-01-07 18:49                               ` Dan Williams
2020-01-07 19:02                                 ` Darrick J. Wong
2020-01-07 19:46                                   ` Dan Williams
2020-01-07 23:38                                     ` Dan Williams
2020-01-09 11:24                                 ` Jan Kara
2020-01-09 20:03                                   ` Dan Williams
2020-01-10 12:36                                     ` Christoph Hellwig
2020-01-14 20:31                                     ` Vivek Goyal
2020-01-14 20:39                                       ` Dan Williams
2020-01-14 21:28                                         ` Vivek Goyal
2020-01-14 22:23                                           ` Dan Williams
2020-01-15 19:56                                             ` Vivek Goyal
2020-01-15 20:17                                               ` Dan Williams
2020-01-15 21:08                                                 ` Jeff Moyer
2020-01-16 18:09                                                   ` Dan Williams
2020-01-16 18:39                                                     ` Vivek Goyal
2020-01-16 19:09                                                       ` Dan Williams
2020-01-16 19:23                                                         ` Vivek Goyal
2020-02-11 17:33                                                     ` Vivek Goyal
2020-01-15  9:03                                           ` Jan Kara
2019-08-21 17:57 ` [PATCH 02/19] dax: Pass dax_dev to dax_writeback_mapping_range() Vivek Goyal
2019-08-26 11:53   ` Christoph Hellwig
2019-08-26 20:33     ` Vivek Goyal
2019-08-26 20:58       ` Vivek Goyal [this message]
2019-08-26 21:33         ` Dan Williams
2019-08-28  6:58         ` Christoph Hellwig
2020-01-03 14:12         ` Vivek Goyal
2020-01-03 18:12           ` Dan Williams
2020-01-03 18:18             ` Dan Williams
2020-01-03 18:33               ` Vivek Goyal
2020-01-03 19:30                 ` Dan Williams
2020-01-03 18:43               ` Vivek Goyal
2019-08-27 13:45       ` Jan Kara
2019-08-21 17:57 ` [PATCH 03/19] virtio: Add get_shm_region method Vivek Goyal
2019-08-21 17:57 ` [PATCH 04/19] virtio: Implement get_shm_region for PCI transport Vivek Goyal
2019-08-26  1:43   ` [Virtio-fs] " piaojun
2019-08-26 13:06     ` Vivek Goyal
2019-08-27  9:41       ` piaojun
2019-08-27  8:34   ` Cornelia Huck
2019-08-27  8:46     ` Cornelia Huck
2019-08-27 11:53     ` Vivek Goyal
2019-08-21 17:57 ` [PATCH 05/19] virtio: Implement get_shm_region for MMIO transport Vivek Goyal
2019-08-27  8:39   ` Cornelia Huck
2019-08-27 11:54     ` Vivek Goyal
2019-08-21 17:57 ` [PATCH 06/19] fuse, dax: add fuse_conn->dax_dev field Vivek Goyal
2019-08-21 17:57 ` [PATCH 07/19] virtio_fs, dax: Set up virtio_fs dax_device Vivek Goyal
2019-08-21 17:57 ` [PATCH 08/19] fuse: Keep a list of free dax memory ranges Vivek Goyal
2019-08-21 17:57 ` [PATCH 09/19] fuse: implement FUSE_INIT map_alignment field Vivek Goyal
2019-08-21 17:57 ` [PATCH 10/19] fuse: Introduce setupmapping/removemapping commands Vivek Goyal
2019-08-21 17:57 ` [PATCH 11/19] fuse, dax: Implement dax read/write operations Vivek Goyal
2019-08-21 19:49   ` Liu Bo
2019-08-22 12:59     ` Vivek Goyal
2019-08-21 17:57 ` [PATCH 12/19] fuse, dax: add DAX mmap support Vivek Goyal
2019-08-21 17:57 ` [PATCH 13/19] fuse: Define dax address space operations Vivek Goyal
2019-08-21 17:57 ` [PATCH 14/19] fuse, dax: Take ->i_mmap_sem lock during dax page fault Vivek Goyal
2019-08-21 17:57 ` [PATCH 15/19] fuse: Maintain a list of busy elements Vivek Goyal
2019-08-21 17:57 ` [PATCH 16/19] dax: Create a range version of dax_layout_busy_page() Vivek Goyal
2019-08-21 17:57 ` [PATCH 17/19] fuse: Add logic to free up a memory range Vivek Goyal
2019-08-21 17:57 ` [PATCH 18/19] fuse: Release file in process context Vivek Goyal
2019-08-21 17:57 ` [PATCH 19/19] fuse: Take inode lock for dax inode truncation Vivek Goyal

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