Merge tag 'fuse-fixes-6.7-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse fixes from Miklos Szeredi:

 - Fix a couple of potential crashes, one introduced in 6.6 and one
   in 5.10

 - Fix misbehavior of virtiofs submounts on memory pressure

 - Clarify naming in the uAPI for a recent feature

* tag 'fuse-fixes-6.7-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: disable FOPEN_PARALLEL_DIRECT_WRITES with FUSE_DIRECT_IO_ALLOW_MMAP
  fuse: dax: set fc->dax to NULL in fuse_dax_conn_free()
  fuse: share lookup state between submount and its parent
  docs/fuse-io: Document the usage of DIRECT_IO_ALLOW_MMAP
  fuse: Rename DIRECT_IO_RELAX to DIRECT_IO_ALLOW_MMAP

Documentation/filesystems/fuse-io.rst

@@ -15,7 +15,8 @@ The direct-io mode can be selected with the FOPEN_DIRECT_IO flag in the
 FUSE_OPEN reply.
 
 In direct-io mode the page cache is completely bypassed for reads and writes.
-No read-ahead takes place. Shared mmap is disabled.
+No read-ahead takes place. Shared mmap is disabled by default. To allow shared
+mmap, the FUSE_DIRECT_IO_ALLOW_MMAP flag may be enabled in the FUSE_INIT reply.
 
 In cached mode reads may be satisfied from the page cache, and data may be
 read-ahead by the kernel to fill the cache.  The cache is always kept consistent

fs/fuse/dax.c

@@ -1222,6 +1222,7 @@ void fuse_dax_conn_free(struct fuse_conn *fc)
 	if (fc->dax) {
 		fuse_free_dax_mem_ranges(&fc->dax->free_ranges);
 		kfree(fc->dax);
+		fc->dax = NULL;
 	}
 }
 

fs/fuse/file.c

@@ -1448,7 +1448,7 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
 	if (!ia)
 		return -ENOMEM;
 
-	if (fopen_direct_io && fc->direct_io_relax) {
+	if (fopen_direct_io && fc->direct_io_allow_mmap) {
 		res = filemap_write_and_wait_range(mapping, pos, pos + count - 1);
 		if (res) {
 			fuse_io_free(ia);
@@ -1574,6 +1574,7 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ssize_t res;
 	bool exclusive_lock =
 		!(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES) ||
+		get_fuse_conn(inode)->direct_io_allow_mmap ||
 		iocb->ki_flags & IOCB_APPEND ||
 		fuse_direct_write_extending_i_size(iocb, from);
 
@@ -1581,6 +1582,7 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	 * Take exclusive lock if
 	 * - Parallel direct writes are disabled - a user space decision
 	 * - Parallel direct writes are enabled and i_size is being extended.
+	 * - Shared mmap on direct_io file is supported (FUSE_DIRECT_IO_ALLOW_MMAP).
 	 *   This might not be needed at all, but needs further investigation.
 	 */
 	if (exclusive_lock)
@@ -2466,9 +2468,9 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
 
 	if (ff->open_flags & FOPEN_DIRECT_IO) {
 		/* Can't provide the coherency needed for MAP_SHARED
-		 * if FUSE_DIRECT_IO_RELAX isn't set.
+		 * if FUSE_DIRECT_IO_ALLOW_MMAP isn't set.
 		 */
-		if ((vma->vm_flags & VM_MAYSHARE) && !fc->direct_io_relax)
+		if ((vma->vm_flags & VM_MAYSHARE) && !fc->direct_io_allow_mmap)
 			return -ENODEV;
 
 		invalidate_inode_pages2(file->f_mapping);

fs/fuse/fuse_i.h

@@ -63,6 +63,19 @@ struct fuse_forget_link {
 	struct fuse_forget_link *next;
 };
 
+/* Submount lookup tracking */
+struct fuse_submount_lookup {
+	/** Refcount */
+	refcount_t count;
+
+	/** Unique ID, which identifies the inode between userspace
+	 * and kernel */
+	u64 nodeid;
+
+	/** The request used for sending the FORGET message */
+	struct fuse_forget_link *forget;
+};
+
 /** FUSE inode */
 struct fuse_inode {
 	/** Inode data */
@@ -158,6 +171,8 @@ struct fuse_inode {
 	 */
 	struct fuse_inode_dax *dax;
 #endif
+	/** Submount specific lookup tracking */
+	struct fuse_submount_lookup *submount_lookup;
 };
 
 /** FUSE inode state bits */
@@ -797,8 +812,8 @@ struct fuse_conn {
 	/* Is tmpfile not implemented by fs? */
 	unsigned int no_tmpfile:1;
 
-	/* relax restrictions in FOPEN_DIRECT_IO mode */
-	unsigned int direct_io_relax:1;
+	/* Relax restrictions to allow shared mmap in FOPEN_DIRECT_IO mode */
+	unsigned int direct_io_allow_mmap:1;
 
 	/* Is statx not implemented by fs? */
 	unsigned int no_statx:1;

fs/fuse/inode.c

@@ -68,6 +68,24 @@ struct fuse_forget_link *fuse_alloc_forget(void)
 	return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL_ACCOUNT);
 }
 
+static struct fuse_submount_lookup *fuse_alloc_submount_lookup(void)
+{
+	struct fuse_submount_lookup *sl;
+
+	sl = kzalloc(sizeof(struct fuse_submount_lookup), GFP_KERNEL_ACCOUNT);
+	if (!sl)
+		return NULL;
+	sl->forget = fuse_alloc_forget();
+	if (!sl->forget)
+		goto out_free;
+
+	return sl;
+
+out_free:
+	kfree(sl);
+	return NULL;
+}
+
 static struct inode *fuse_alloc_inode(struct super_block *sb)
 {
 	struct fuse_inode *fi;
@@ -83,6 +101,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
 	fi->attr_version = 0;
 	fi->orig_ino = 0;
 	fi->state = 0;
+	fi->submount_lookup = NULL;
 	mutex_init(&fi->mutex);
 	spin_lock_init(&fi->lock);
 	fi->forget = fuse_alloc_forget();
@@ -113,6 +132,17 @@ static void fuse_free_inode(struct inode *inode)
 	kmem_cache_free(fuse_inode_cachep, fi);
 }
 
+static void fuse_cleanup_submount_lookup(struct fuse_conn *fc,
+					 struct fuse_submount_lookup *sl)
+{
+	if (!refcount_dec_and_test(&sl->count))
+		return;
+
+	fuse_queue_forget(fc, sl->forget, sl->nodeid, 1);
+	sl->forget = NULL;
+	kfree(sl);
+}
+
 static void fuse_evict_inode(struct inode *inode)
 {
 	struct fuse_inode *fi = get_fuse_inode(inode);
@@ -132,6 +162,11 @@ static void fuse_evict_inode(struct inode *inode)
 					  fi->nlookup);
 			fi->forget = NULL;
 		}
+
+		if (fi->submount_lookup) {
+			fuse_cleanup_submount_lookup(fc, fi->submount_lookup);
+			fi->submount_lookup = NULL;
+		}
 	}
 	if (S_ISREG(inode->i_mode) && !fuse_is_bad(inode)) {
 		WARN_ON(!list_empty(&fi->write_files));
@@ -330,6 +365,13 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
 		fuse_dax_dontcache(inode, attr->flags);
 }
 
+static void fuse_init_submount_lookup(struct fuse_submount_lookup *sl,
+				      u64 nodeid)
+{
+	sl->nodeid = nodeid;
+	refcount_set(&sl->count, 1);
+}
+
 static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr,
 			    struct fuse_conn *fc)
 {
@@ -392,12 +434,22 @@ struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
 	 */
 	if (fc->auto_submounts && (attr->flags & FUSE_ATTR_SUBMOUNT) &&
 	    S_ISDIR(attr->mode)) {
+		struct fuse_inode *fi;
+
 		inode = new_inode(sb);
 		if (!inode)
 			return NULL;
 
 		fuse_init_inode(inode, attr, fc);
-		get_fuse_inode(inode)->nodeid = nodeid;
+		fi = get_fuse_inode(inode);
+		fi->nodeid = nodeid;
+		fi->submount_lookup = fuse_alloc_submount_lookup();
+		if (!fi->submount_lookup) {
+			iput(inode);
+			return NULL;
+		}
+		/* Sets nlookup = 1 on fi->submount_lookup->nlookup */
+		fuse_init_submount_lookup(fi->submount_lookup, nodeid);
 		inode->i_flags |= S_AUTOMOUNT;
 		goto done;
 	}
@@ -420,11 +472,11 @@ struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
 		iput(inode);
 		goto retry;
 	}
-done:
 	fi = get_fuse_inode(inode);
 	spin_lock(&fi->lock);
 	fi->nlookup++;
 	spin_unlock(&fi->lock);
+done:
 	fuse_change_attributes(inode, attr, NULL, attr_valid, attr_version);
 
 	return inode;
@@ -1230,8 +1282,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
 				fc->init_security = 1;
 			if (flags & FUSE_CREATE_SUPP_GROUP)
 				fc->create_supp_group = 1;
-			if (flags & FUSE_DIRECT_IO_RELAX)
-				fc->direct_io_relax = 1;
+			if (flags & FUSE_DIRECT_IO_ALLOW_MMAP)
+				fc->direct_io_allow_mmap = 1;
 		} else {
 			ra_pages = fc->max_read / PAGE_SIZE;
 			fc->no_lock = 1;
@@ -1278,7 +1330,7 @@ void fuse_send_init(struct fuse_mount *fm)
 		FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
 		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_INIT_EXT |
 		FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP |
-		FUSE_HAS_EXPIRE_ONLY | FUSE_DIRECT_IO_RELAX;
+		FUSE_HAS_EXPIRE_ONLY | FUSE_DIRECT_IO_ALLOW_MMAP;
 #ifdef CONFIG_FUSE_DAX
 	if (fm->fc->dax)
 		flags |= FUSE_MAP_ALIGNMENT;
@@ -1465,6 +1517,8 @@ static int fuse_fill_super_submount(struct super_block *sb,
 	struct super_block *parent_sb = parent_fi->inode.i_sb;
 	struct fuse_attr root_attr;
 	struct inode *root;
+	struct fuse_submount_lookup *sl;
+	struct fuse_inode *fi;
 
 	fuse_sb_defaults(sb);
 	fm->sb = sb;
@@ -1487,12 +1541,27 @@ static int fuse_fill_super_submount(struct super_block *sb,
 	 * its nlookup should not be incremented.  fuse_iget() does
 	 * that, though, so undo it here.
 	 */
-	get_fuse_inode(root)->nlookup--;
+	fi = get_fuse_inode(root);
+	fi->nlookup--;
+
 	sb->s_d_op = &fuse_dentry_operations;
 	sb->s_root = d_make_root(root);
 	if (!sb->s_root)
 		return -ENOMEM;
 
+	/*
+	 * Grab the parent's submount_lookup pointer and take a
+	 * reference on the shared nlookup from the parent.  This is to
+	 * prevent the last forget for this nodeid from getting
+	 * triggered until all users have finished with it.
+	 */
+	sl = parent_fi->submount_lookup;
+	WARN_ON(!sl);
+	if (sl) {
+		refcount_inc(&sl->count);
+		fi->submount_lookup = sl;
+	}
+
 	return 0;
 }
 

include/uapi/linux/fuse.h

@@ -209,7 +209,7 @@
  *  - add FUSE_HAS_EXPIRE_ONLY
  *
  *  7.39
- *  - add FUSE_DIRECT_IO_RELAX
+ *  - add FUSE_DIRECT_IO_ALLOW_MMAP
  *  - add FUSE_STATX and related structures
  */
 
@@ -409,8 +409,7 @@ struct fuse_file_lock {
  * FUSE_CREATE_SUPP_GROUP: add supplementary group info to create, mkdir,
  *			symlink and mknod (single group that matches parent)
  * FUSE_HAS_EXPIRE_ONLY: kernel supports expiry-only entry invalidation
- * FUSE_DIRECT_IO_RELAX: relax restrictions in FOPEN_DIRECT_IO mode, for now
- *                       allow shared mmap
+ * FUSE_DIRECT_IO_ALLOW_MMAP: allow shared mmap in FOPEN_DIRECT_IO mode.
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -449,7 +448,10 @@ struct fuse_file_lock {
 #define FUSE_HAS_INODE_DAX	(1ULL << 33)
 #define FUSE_CREATE_SUPP_GROUP	(1ULL << 34)
 #define FUSE_HAS_EXPIRE_ONLY	(1ULL << 35)
-#define FUSE_DIRECT_IO_RELAX	(1ULL << 36)
+#define FUSE_DIRECT_IO_ALLOW_MMAP (1ULL << 36)
+
+/* Obsolete alias for FUSE_DIRECT_IO_ALLOW_MMAP */
+#define FUSE_DIRECT_IO_RELAX	FUSE_DIRECT_IO_ALLOW_MMAP
 
 /**
  * CUSE INIT request/reply flags