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Date:   Thu, 08 Feb 2018 17:38:13 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     darrick.wong@...cle.com
Cc:     linux-nvdimm@...ts.01.org, david@...morbit.com,
        linux-xfs@...r.kernel.org, ross.zwisler@...ux.intel.com,
        linux-ext4@...r.kernel.org, dan.j.williams@...el.com
Subject: [PATCH v3 1/3] fs: allow per-device dax status checking for
 filesystems

From: Darrick J. Wong <darrick.wong@...cle.com>

Refactor __bdev_dax_supported into a sb_dax_supported helper for
single-bdev filesystems and a regular bdev_dax_supported that takes a
bdev parameter.  This enables multi-device filesystems like xfs to check
that a dax device can work for the particular filesystem.  Once that's
in place, actually fix all the parts of XFS where we need to be able to
distinguish between datadev and rtdev.

This patch fixes the problem where we screw up the dax support checking
in xfs if the datadev and rtdev have different dax capabilities.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 drivers/dax/super.c |    9 +++++----
 fs/ext2/super.c     |    2 +-
 fs/ext4/super.c     |    2 +-
 fs/xfs/xfs_ioctl.c  |    3 ++-
 fs/xfs/xfs_iops.c   |   30 +++++++++++++++++++++++++-----
 fs/xfs/xfs_super.c  |   11 +++++++++--
 include/linux/dax.h |   16 ++++++++++++----
 7 files changed, 55 insertions(+), 18 deletions(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 3ec804672601..c4db84f26c0f 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -72,8 +72,9 @@ EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
 #endif
 
 /**
- * __bdev_dax_supported() - Check if the device supports dax for filesystem
+ * bdev_dax_supported() - Check if the device supports dax for filesystem
  * @sb: The superblock of the device
+ * @bdev: block device to check
  * @blocksize: The block size of the device
  *
  * This is a library function for filesystems to check if the block device
@@ -81,9 +82,9 @@ EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
  *
  * Return: negative errno if unsupported, 0 if supported.
  */
-int __bdev_dax_supported(struct super_block *sb, int blocksize)
+int bdev_dax_supported(struct super_block *sb, struct block_device *bdev,
+		       int blocksize)
 {
-	struct block_device *bdev = sb->s_bdev;
 	struct dax_device *dax_dev;
 	pgoff_t pgoff;
 	int err, id;
@@ -125,7 +126,7 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize)
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(__bdev_dax_supported);
+EXPORT_SYMBOL_GPL(bdev_dax_supported);
 #endif
 
 enum dax_device_flags {
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 7646818ab266..655699321c45 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -958,7 +958,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);
 
 	if (sbi->s_mount_opt & EXT2_MOUNT_DAX) {
-		err = bdev_dax_supported(sb, blocksize);
+		err = sb_dax_supported(sb, blocksize);
 		if (err)
 			goto failed_mount;
 	}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7c46693a14d7..804a2d6729af 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3712,7 +3712,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 					" that may contain inline data");
 			goto failed_mount;
 		}
-		err = bdev_dax_supported(sb, blocksize);
+		err = sb_dax_supported(sb, blocksize);
 		if (err)
 			goto failed_mount;
 	}
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 20dc65fef6a4..f9d3f4314f7c 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1102,7 +1102,8 @@ xfs_ioctl_setattr_dax_invalidate(
 	if (fa->fsx_xflags & FS_XFLAG_DAX) {
 		if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
 			return -EINVAL;
-		if (bdev_dax_supported(sb, sb->s_blocksize) < 0)
+		if (bdev_dax_supported(sb, xfs_find_bdev_for_inode(VFS_I(ip)),
+				sb->s_blocksize) < 0)
 			return -EINVAL;
 	}
 
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 56475fcd76f2..66cd61c172af 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1182,6 +1182,30 @@ static const struct inode_operations xfs_inline_symlink_inode_operations = {
 	.update_time		= xfs_vn_update_time,
 };
 
+/* Figure out if this file actually supports DAX. */
+static bool
+xfs_inode_supports_dax(
+	struct xfs_inode	*ip)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+
+	/* Only supported on non-reflinked files. */
+	if (!S_ISREG(VFS_I(ip)->i_mode) || xfs_is_reflink_inode(ip))
+		return false;
+
+	/* DAX mount option or DAX iflag must be set. */
+	if (!(mp->m_flags & XFS_MOUNT_DAX) &&
+	    !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
+		return false;
+
+	/* Block size must match page size */
+	if (mp->m_sb.sb_blocksize != PAGE_SIZE)
+		return false;
+
+	/* Device has to support DAX too. */
+	return xfs_find_daxdev_for_inode(VFS_I(ip)) != NULL;
+}
+
 STATIC void
 xfs_diflags_to_iflags(
 	struct inode		*inode,
@@ -1200,11 +1224,7 @@ xfs_diflags_to_iflags(
 		inode->i_flags |= S_SYNC;
 	if (flags & XFS_DIFLAG_NOATIME)
 		inode->i_flags |= S_NOATIME;
-	if (S_ISREG(inode->i_mode) &&
-	    ip->i_mount->m_sb.sb_blocksize == PAGE_SIZE &&
-	    !xfs_is_reflink_inode(ip) &&
-	    (ip->i_mount->m_flags & XFS_MOUNT_DAX ||
-	     ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
+	if (xfs_inode_supports_dax(ip))
 		inode->i_flags |= S_DAX;
 }
 
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 1dacccc367f8..5fd60c1fa9db 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1649,11 +1649,18 @@ xfs_fs_fill_super(
 		sb->s_flags |= SB_I_VERSION;
 
 	if (mp->m_flags & XFS_MOUNT_DAX) {
+		int	error2 = 0;
+
 		xfs_warn(mp,
 		"DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
 
-		error = bdev_dax_supported(sb, sb->s_blocksize);
-		if (error) {
+		error = bdev_dax_supported(sb, mp->m_ddev_targp->bt_bdev,
+				sb->s_blocksize);
+		if (mp->m_rtdev_targp)
+			error2 = bdev_dax_supported(sb,
+					mp->m_rtdev_targp->bt_bdev,
+					sb->s_blocksize);
+		if (error && error2) {
 			xfs_alert(mp,
 			"DAX unsupported by block device. Turning off DAX.");
 			mp->m_flags &= ~XFS_MOUNT_DAX;
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 5258346c558c..1107a980f5c3 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -40,10 +40,11 @@ static inline void put_dax(struct dax_device *dax_dev)
 
 int bdev_dax_pgoff(struct block_device *, sector_t, size_t, pgoff_t *pgoff);
 #if IS_ENABLED(CONFIG_FS_DAX)
-int __bdev_dax_supported(struct super_block *sb, int blocksize);
-static inline int bdev_dax_supported(struct super_block *sb, int blocksize)
+int bdev_dax_supported(struct super_block *sb, struct block_device *bdev,
+		       int blocksize);
+static inline int sb_dax_supported(struct super_block *sb, int blocksize)
 {
-	return __bdev_dax_supported(sb, blocksize);
+	return bdev_dax_supported(sb, sb->s_bdev, blocksize);
 }
 
 static inline struct dax_device *fs_dax_get_by_host(const char *host)
@@ -58,7 +59,14 @@ static inline void fs_put_dax(struct dax_device *dax_dev)
 
 struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
 #else
-static inline int bdev_dax_supported(struct super_block *sb, int blocksize)
+static inline int bdev_dax_supported(struct super_block *sb,
+				     struct block_device *bdev,
+				     int blocksize)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int sb_dax_supported(struct super_block *sb, int blocksize)
 {
 	return -EOPNOTSUPP;
 }

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