[RFC PATCH 6/7] fuse: Introduce fuse_dax_is_supported()

[Mathieu Desnoyers]

Use dax_is_supported() in addition to IS_ENABLED(CONFIG_FUSE_DAX) to
validate whether CONFIG_FUSE_DAX is enabled and the architecture does
not have virtually aliased caches.

This is relevant for architectures which require a dynamic check
to validate whether they have virtually aliased data caches
(ARCH_HAS_CACHE_ALIASING_DYNAMIC=y).

Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: nvdimm@xxxxxxxxxxxxxxx
Cc: linux-cxl@xxxxxxxxxxxxxxx
---
 fs/fuse/file.c      |  2 +-
 fs/fuse/fuse_i.h    | 36 +++++++++++++++++++++++++++++++++-
 fs/fuse/inode.c     | 47 +++++++++++++++++++++++----------------------
 fs/fuse/virtio_fs.c |  4 ++--
 4 files changed, 62 insertions(+), 27 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a660f1f21540..133ac8524064 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -3247,6 +3247,6 @@ void fuse_init_file_inode(struct inode *inode, unsigned int flags)
 	init_waitqueue_head(&fi->page_waitq);
 	fi->writepages = RB_ROOT;
 
-	if (IS_ENABLED(CONFIG_FUSE_DAX))
+	if (fuse_dax_is_supported())
 		fuse_dax_inode_init(inode, flags);
 }
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 1df83eebda92..1cbe37106669 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -31,6 +31,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/refcount.h>
 #include <linux/user_namespace.h>
+#include <linux/dax.h>
 
 /** Default max number of pages that can be used in a single read request */
 #define FUSE_DEFAULT_MAX_PAGES_PER_REQ 32
@@ -979,6 +980,38 @@ static inline void fuse_sync_bucket_dec(struct fuse_sync_bucket *bucket)
 	rcu_read_unlock();
 }
 
+#ifdef CONFIG_FUSE_DAX
+static inline struct fuse_inode_dax *fuse_inode_get_dax(struct fuse_inode *inode)
+{
+	return inode->dax;
+}
+
+static inline enum fuse_dax_mode fuse_conn_get_dax_mode(struct fuse_conn *fc)
+{
+	return fc->dax_mode;
+}
+
+static inline struct fuse_conn_dax *fuse_conn_get_dax(struct fuse_conn *fc)
+{
+	return fc->dax;
+}
+#else
+static inline struct fuse_inode_dax *fuse_inode_get_dax(struct fuse_inode *inode)
+{
+	return NULL;
+}
+
+static inline enum fuse_dax_mode fuse_conn_get_dax_mode(struct fuse_conn *fc)
+{
+	return FUSE_DAX_INODE_DEFAULT;
+}
+
+static inline struct fuse_conn_dax *fuse_conn_get_dax(struct fuse_conn *fc)
+{
+	return NULL;
+}
+#endif
+
 /** Device operations */
 extern const struct file_operations fuse_dev_operations;
 
@@ -1324,7 +1357,8 @@ void fuse_free_conn(struct fuse_conn *fc);
 
 /* dax.c */
 
-#define FUSE_IS_DAX(inode) (IS_ENABLED(CONFIG_FUSE_DAX) && IS_DAX(inode))
+#define fuse_dax_is_supported()	(IS_ENABLED(CONFIG_FUSE_DAX) && dax_is_supported())
+#define FUSE_IS_DAX(inode) (fuse_dax_is_supported() && IS_DAX(inode))
 
 ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to);
 ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 2a6d44f91729..030e6ce5486d 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -108,7 +108,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
 	if (!fi->forget)
 		goto out_free;
 
-	if (IS_ENABLED(CONFIG_FUSE_DAX) && !fuse_dax_inode_alloc(sb, fi))
+	if (fuse_dax_is_supported() && !fuse_dax_inode_alloc(sb, fi))
 		goto out_free_forget;
 
 	return &fi->inode;
@@ -126,9 +126,8 @@ static void fuse_free_inode(struct inode *inode)
 
 	mutex_destroy(&fi->mutex);
 	kfree(fi->forget);
-#ifdef CONFIG_FUSE_DAX
-	kfree(fi->dax);
-#endif
+	if (fuse_dax_is_supported())
+		kfree(fuse_inode_get_dax(fi));
 	kmem_cache_free(fuse_inode_cachep, fi);
 }
 
@@ -361,7 +360,7 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
 			invalidate_inode_pages2(inode->i_mapping);
 	}
 
-	if (IS_ENABLED(CONFIG_FUSE_DAX))
+	if (fuse_dax_is_supported())
 		fuse_dax_dontcache(inode, attr->flags);
 }
 
@@ -856,14 +855,16 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
 		if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
 			seq_printf(m, ",blksize=%lu", sb->s_blocksize);
 	}
-#ifdef CONFIG_FUSE_DAX
-	if (fc->dax_mode == FUSE_DAX_ALWAYS)
-		seq_puts(m, ",dax=always");
-	else if (fc->dax_mode == FUSE_DAX_NEVER)
-		seq_puts(m, ",dax=never");
-	else if (fc->dax_mode == FUSE_DAX_INODE_USER)
-		seq_puts(m, ",dax=inode");
-#endif
+	if (fuse_dax_is_supported()) {
+		enum fuse_dax_mode dax_mode = fuse_conn_get_dax_mode(fc);
+
+		if (dax_mode == FUSE_DAX_ALWAYS)
+			seq_puts(m, ",dax=always");
+		else if (dax_mode == FUSE_DAX_NEVER)
+			seq_puts(m, ",dax=never");
+		else if (dax_mode == FUSE_DAX_INODE_USER)
+			seq_puts(m, ",dax=inode");
+	}
 
 	return 0;
 }
@@ -936,7 +937,7 @@ void fuse_conn_put(struct fuse_conn *fc)
 		struct fuse_iqueue *fiq = &fc->iq;
 		struct fuse_sync_bucket *bucket;
 
-		if (IS_ENABLED(CONFIG_FUSE_DAX))
+		if (fuse_dax_is_supported())
 			fuse_dax_conn_free(fc);
 		if (fiq->ops->release)
 			fiq->ops->release(fiq);
@@ -1264,7 +1265,7 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
 					min_t(unsigned int, fc->max_pages_limit,
 					max_t(unsigned int, arg->max_pages, 1));
 			}
-			if (IS_ENABLED(CONFIG_FUSE_DAX)) {
+			if (fuse_dax_is_supported()) {
 				if (flags & FUSE_MAP_ALIGNMENT &&
 				    !fuse_dax_check_alignment(fc, arg->map_alignment)) {
 					ok = false;
@@ -1331,12 +1332,12 @@ void fuse_send_init(struct fuse_mount *fm)
 		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_INIT_EXT |
 		FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP |
 		FUSE_HAS_EXPIRE_ONLY | FUSE_DIRECT_IO_ALLOW_MMAP;
-#ifdef CONFIG_FUSE_DAX
-	if (fm->fc->dax)
-		flags |= FUSE_MAP_ALIGNMENT;
-	if (fuse_is_inode_dax_mode(fm->fc->dax_mode))
-		flags |= FUSE_HAS_INODE_DAX;
-#endif
+	if (fuse_dax_is_supported()) {
+		if (fuse_conn_get_dax(fm->fc))
+			flags |= FUSE_MAP_ALIGNMENT;
+		if (fuse_is_inode_dax_mode(fuse_conn_get_dax_mode(fm->fc)))
+			flags |= FUSE_HAS_INODE_DAX;
+	}
 	if (fm->fc->auto_submounts)
 		flags |= FUSE_SUBMOUNTS;
 
@@ -1643,7 +1644,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 
 	sb->s_subtype = ctx->subtype;
 	ctx->subtype = NULL;
-	if (IS_ENABLED(CONFIG_FUSE_DAX)) {
+	if (fuse_dax_is_supported()) {
 		err = fuse_dax_conn_alloc(fc, ctx->dax_mode, ctx->dax_dev);
 		if (err)
 			goto err;
@@ -1709,7 +1710,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 	if (fud)
 		fuse_dev_free(fud);
  err_free_dax:
-	if (IS_ENABLED(CONFIG_FUSE_DAX))
+	if (fuse_dax_is_supported())
 		fuse_dax_conn_free(fc);
  err:
 	return err;
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 5f1be1da92ce..99f8f2a18ee4 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -801,7 +801,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
 	struct dev_pagemap *pgmap;
 	bool have_cache;
 
-	if (!IS_ENABLED(CONFIG_FUSE_DAX))
+	if (fuse_dax_is_supported())
 		return 0;
 
 	/* Get cache region */
@@ -1366,7 +1366,7 @@ static void virtio_fs_conn_destroy(struct fuse_mount *fm)
 	/* Stop dax worker. Soon evict_inodes() will be called which
 	 * will free all memory ranges belonging to all inodes.
 	 */
-	if (IS_ENABLED(CONFIG_FUSE_DAX))
+	if (fuse_dax_is_supported())
 		fuse_dax_cancel_work(fc);
 
 	/* Stop forget queue. Soon destroy will be sent */
-- 
2.39.2