dax: Avoid ABI change in 4.17.6

The return type and first parameter type for bdev_dax_supported() and
__bdev_dax_supported() were changed by commits ba23cba9b3bd "fs: allow
per-device dax status checking for filesystems" and 80660f20252d "dax:
change bdev_dax_supported() to support boolean returns".

Avoid an ABI break by renaming the new version of
__bdev_dax_supported() and reintroducing the old version as a wrapper
for it.  Add a #define so that the old version is hidden from the API,
i.e. newly built modules must use the new API.

Gbp-Pq: Topic debian
Gbp-Pq: Name dax-avoid-abi-change-in-4.17.6.patch

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 1d2de641cabb95a2459e4f6f90e55618ff9b9c7c..f446c2a54e301b37f2adb08b75c37204739462c7 100644 (file)
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -72,6 +72,8 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
 EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
 #endif
 
+#undef __bdev_dax_supported
+
 /**
  * __bdev_dax_supported() - Check if the device supports dax for filesystem
  * @bdev: block device to check
@@ -82,7 +84,7 @@ EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
  *
  * Return: true if supported, false if unsupported
  */
-bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
+bool __bdev_dax_supported_new(struct block_device *bdev, int blocksize)
 {
        struct dax_device *dax_dev;
        struct request_queue *q;
@@ -152,6 +154,13 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
 
        return true;
 }
+EXPORT_SYMBOL_GPL(__bdev_dax_supported_new);
+
+int __bdev_dax_supported(struct super_block *sb, int blocksize)
+{
+       return __bdev_dax_supported_new(sb->s_bdev, blocksize)
+               ? 0 : -EOPNOTSUPP;
+}
 EXPORT_SYMBOL_GPL(__bdev_dax_supported);
 #endif
 

diff --git a/include/linux/dax.h b/include/linux/dax.h
index c99692ddd4b5568ee79c64a6536352357c1f864a..3d9a90cb43512a353efe2aebf6be7f0d7ba34171 100644 (file)
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -64,7 +64,9 @@ 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)
-bool __bdev_dax_supported(struct block_device *bdev, int blocksize);
+int __bdev_dax_supported(struct super_block *sb, int blocksize);
+bool __bdev_dax_supported_new(struct block_device *bdev, int blocksize);
+#define __bdev_dax_supported __bdev_dax_supported_new
 static inline bool bdev_dax_supported(struct block_device *bdev, int blocksize)
 {
        return __bdev_dax_supported(bdev, blocksize);