dax: change bdev_dax_supported() to support boolean returns

The function return values are confusing with the way the function is
named. We expect a true or false return value but it actually returns
0/-errno.  This makes the code very confusing. Changing the return values
to return a bool where if DAX is supported then return true and no DAX
support returns false.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

6 files changed, 22 insertions, 24 deletions

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 3943feb9a090..1d7bd96511f0 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -80,9 +80,9 @@ EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
  * This is a library function for filesystems to check if the block device
  * can be mounted with dax option.
  *
- * Return: negative errno if unsupported, 0 if supported.
+ * Return: true if supported, false if unsupported
  */
-int __bdev_dax_supported(struct block_device *bdev, int blocksize)
+bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
 {
         struct dax_device *dax_dev;
         pgoff_t pgoff;
@@ -95,21 +95,21 @@ int __bdev_dax_supported(struct block_device *bdev, int blocksize)
         if (blocksize != PAGE_SIZE) {
                 pr_debug("%s: error: unsupported blocksize for dax\n",
                                 bdevname(bdev, buf));
-                return -EINVAL;
+                return false;
         }
 
         err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff);
         if (err) {
                 pr_debug("%s: error: unaligned partition for dax\n",
                                 bdevname(bdev, buf));
-                return err;
+                return false;
         }
 
         dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
         if (!dax_dev) {
                 pr_debug("%s: error: device does not support dax\n",
                                 bdevname(bdev, buf));
-                return -EOPNOTSUPP;
+                return false;
         }
 
         id = dax_read_lock();
@@ -121,7 +121,7 @@ int __bdev_dax_supported(struct block_device *bdev, int blocksize)
         if (len < 1) {
                 pr_debug("%s: error: dax access failed (%ld)\n",
                                 bdevname(bdev, buf), len);
-                return len < 0 ? len : -EIO;
+                return false;
         }
 
         if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) {
@@ -139,10 +139,10 @@ int __bdev_dax_supported(struct block_device *bdev, int blocksize)
         } else {
                 pr_debug("%s: error: dax support not enabled\n",
                                 bdevname(bdev, buf));
-                return -EOPNOTSUPP;
+                return false;
         }
 
-        return 0;
+        return true;
 }
 EXPORT_SYMBOL_GPL(__bdev_dax_supported);
 #endif
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 9627c3054b5c..c09289a42dc5 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -961,8 +961,7 @@ 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->s_bdev, blocksize);
-                if (err) {
+                if (!bdev_dax_supported(sb->s_bdev, blocksize)) {
                         ext2_msg(sb, KERN_ERR,
                                 "DAX unsupported by block device. Turning off DAX.");
                         sbi->s_mount_opt &= ~EXT2_MOUNT_DAX;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 089170e99895..2e1622907f4a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3732,8 +3732,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                                         " that may contain inline data");
                         sbi->s_mount_opt &= ~EXT4_MOUNT_DAX;
                 }
-                err = bdev_dax_supported(sb->s_bdev, blocksize);
-                if (err) {
+                if (!bdev_dax_supported(sb->s_bdev, blocksize)) {
                         ext4_msg(sb, KERN_ERR,
                                 "DAX unsupported by block device. Turning off DAX.");
                         sbi->s_mount_opt &= ~EXT4_MOUNT_DAX;
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index c9a5b75a73a8..5dd9e22b4a4c 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1103,8 +1103,8 @@ 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(xfs_find_bdev_for_inode(VFS_I(ip)),
-                                sb->s_blocksize) < 0)
+                if (!bdev_dax_supported(xfs_find_bdev_for_inode(VFS_I(ip)),
+                                sb->s_blocksize))
                         return -EINVAL;
         }
 
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index fed63e0b8f4d..4e66e61865fb 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1701,17 +1701,17 @@ xfs_fs_fill_super(
                 sb->s_flags |= SB_I_VERSION;
 
         if (mp->m_flags & XFS_MOUNT_DAX) {
-                int     error2 = 0;
+                bool rtdev_is_dax = false, datadev_is_dax;
 
                 xfs_warn(mp,
                 "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
 
-                error = bdev_dax_supported(mp->m_ddev_targp->bt_bdev,
-                                sb->s_blocksize);
+                datadev_is_dax = bdev_dax_supported(mp->m_ddev_targp->bt_bdev,
+                        sb->s_blocksize);
                 if (mp->m_rtdev_targp)
-                        error2 = bdev_dax_supported(mp->m_rtdev_targp->bt_bdev,
-                                        sb->s_blocksize);
-                if (error && error2) {
+                        rtdev_is_dax = bdev_dax_supported(
+                                mp->m_rtdev_targp->bt_bdev, sb->s_blocksize);
+                if (!rtdev_is_dax && !datadev_is_dax) {
                         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 2a4f7295c12b..c99692ddd4b5 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -64,8 +64,8 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
 struct writeback_control;
 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 block_device *bdev, int blocksize);
-static inline int bdev_dax_supported(struct block_device *bdev, int blocksize)
+bool __bdev_dax_supported(struct block_device *bdev, int blocksize);
+static inline bool bdev_dax_supported(struct block_device *bdev, int blocksize)
 {
         return __bdev_dax_supported(bdev, blocksize);
 }
@@ -84,10 +84,10 @@ 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);
 #else
-static inline int bdev_dax_supported(struct block_device *bdev,
+static inline bool bdev_dax_supported(struct block_device *bdev,
                 int blocksize)
 {
-        return -EOPNOTSUPP;
+        return false;
 }
 
 static inline struct dax_device *fs_dax_get_by_host(const char *host)