[PATCH 0/7] fuse updates

[PATCH 0/7] fuse updates

[Miklos Szeredi]

Hi Andrew!

Patches 1 and 2 are bugfixes, and should go into 2.6.15.

The others are cleanups and new features, which can wait for 2.6.16.

Thanks,
Miklos

[PATCH 1/7] fuse: check directory aliasing in mkdir

[Miklos Szeredi]

Check the created directory inode for aliases in the mkdir() method.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

---
Index: linux/fs/fuse/dir.c
===================================================================
--- linux.orig/fs/fuse/dir.c	2005-11-28 14:01:08.000000000 +0100
+++ linux/fs/fuse/dir.c	2005-11-28 14:01:52.000000000 +0100
@@ -74,6 +74,19 @@ static int fuse_dentry_revalidate(struct
 	return 1;
 }
 
+static int dir_alias(struct inode *inode)
+{
+	if (S_ISDIR(inode->i_mode)) {
+		/* Don't allow creating an alias to a directory  */
+		struct dentry *alias = d_find_alias(inode);
+		if (alias) {
+			dput(alias);
+			return 1;
+		}
+	}
+	return 0;
+}
+
 static struct dentry_operations fuse_dentry_operations = {
 	.d_revalidate	= fuse_dentry_revalidate,
 };
@@ -263,7 +276,7 @@ static int create_new_entry(struct fuse_
 	fuse_put_request(fc, req);
 
 	/* Don't allow userspace to do really stupid things... */
-	if ((inode->i_mode ^ mode) & S_IFMT) {
+	if (((inode->i_mode ^ mode) & S_IFMT) || dir_alias(inode)) {
 		iput(inode);
 		return -EIO;
 	}
@@ -874,14 +887,9 @@ static struct dentry *fuse_lookup(struct
 	err = fuse_lookup_iget(dir, entry, &inode);
 	if (err)
 		return ERR_PTR(err);
-	if (inode && S_ISDIR(inode->i_mode)) {
-		/* Don't allow creating an alias to a directory  */
-		struct dentry *alias = d_find_alias(inode);
-		if (alias) {
-			dput(alias);
-			iput(inode);
-			return ERR_PTR(-EIO);
-		}
+	if (inode && dir_alias(inode)) {
+		iput(inode);
+		return ERR_PTR(-EIO);
 	}
 	d_add(entry, inode);
 	return NULL;

[PATCH 2/7] fuse: check for invalid node ID in fuse_create_open()

[Miklos Szeredi]

Check for invalid node ID values in the new atomic create+open method.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

---
Index: linux/fs/fuse/dir.c
===================================================================
--- linux.orig/fs/fuse/dir.c	2005-11-28 17:24:22.000000000 +0100
+++ linux/fs/fuse/dir.c	2005-11-28 17:24:26.000000000 +0100
@@ -87,6 +87,11 @@ static int dir_alias(struct inode *inode
 	return 0;
 }
 
+static inline int invalid_nodeid(u64 nodeid)
+{
+	return !nodeid || nodeid == FUSE_ROOT_ID;
+}
+
 static struct dentry_operations fuse_dentry_operations = {
 	.d_revalidate	= fuse_dentry_revalidate,
 };
@@ -110,7 +115,7 @@ static int fuse_lookup_iget(struct inode
 	fuse_lookup_init(req, dir, entry, &outarg);
 	request_send(fc, req);
 	err = req->out.h.error;
-	if (!err && (!outarg.nodeid || outarg.nodeid == FUSE_ROOT_ID))
+	if (!err && invalid_nodeid(outarg.nodeid))
 		err = -EIO;
 	if (!err) {
 		inode = fuse_iget(dir->i_sb, outarg.nodeid, outarg.generation,
@@ -206,7 +211,7 @@ static int fuse_create_open(struct inode
 	}
 
 	err = -EIO;
-	if (!S_ISREG(outentry.attr.mode))
+	if (!S_ISREG(outentry.attr.mode) || invalid_nodeid(outentry.nodeid))
 		goto out_free_ff;
 
 	inode = fuse_iget(dir->i_sb, outentry.nodeid, outentry.generation,
@@ -263,7 +268,7 @@ static int create_new_entry(struct fuse_
 		fuse_put_request(fc, req);
 		return err;
 	}
-	if (!outarg.nodeid || outarg.nodeid == FUSE_ROOT_ID) {
+	if (invalid_nodeid(outarg.nodeid)) {
 		fuse_put_request(fc, req);
 		return -EIO;
 	}

[PATCH 3/7] fuse: clean up fuse_lookup()

[Miklos Szeredi]

Simplify fuse_lookup() and related functions.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

---
Index: linux/fs/fuse/dir.c
===================================================================
--- linux.orig/fs/fuse/dir.c	2005-11-28 17:24:26.000000000 +0100
+++ linux/fs/fuse/dir.c	2005-11-28 17:26:51.000000000 +0100
@@ -13,7 +13,6 @@
 #include <linux/gfp.h>
 #include <linux/sched.h>
 #include <linux/namei.h>
-#include <linux/mount.h>
 
 static inline unsigned long time_to_jiffies(unsigned long sec,
 					    unsigned long nsec)
@@ -22,6 +21,13 @@ static inline unsigned long time_to_jiff
 	return jiffies + timespec_to_jiffies(&ts);
 }
 
+static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o)
+{
+	struct fuse_inode *fi = get_fuse_inode(entry->d_inode);
+	entry->d_time = time_to_jiffies(o->entry_valid, o->entry_valid_nsec);
+	fi->i_time = time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
+}
+
 static void fuse_lookup_init(struct fuse_req *req, struct inode *dir,
 			     struct dentry *entry,
 			     struct fuse_entry_out *outarg)
@@ -66,10 +72,7 @@ static int fuse_dentry_revalidate(struct
 			return 0;
 
 		fuse_change_attributes(inode, &outarg.attr);
-		entry->d_time = time_to_jiffies(outarg.entry_valid,
-						outarg.entry_valid_nsec);
-		fi->i_time = time_to_jiffies(outarg.attr_valid,
-					     outarg.attr_valid_nsec);
+		fuse_change_timeout(entry, &outarg);
 	}
 	return 1;
 }
@@ -96,8 +99,8 @@ static struct dentry_operations fuse_den
 	.d_revalidate	= fuse_dentry_revalidate,
 };
 
-static int fuse_lookup_iget(struct inode *dir, struct dentry *entry,
-			    struct inode **inodep)
+static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
+				  struct nameidata *nd)
 {
 	int err;
 	struct fuse_entry_out outarg;
@@ -106,11 +109,11 @@ static int fuse_lookup_iget(struct inode
 	struct fuse_req *req;
 
 	if (entry->d_name.len > FUSE_NAME_MAX)
-		return -ENAMETOOLONG;
+		return ERR_PTR(-ENAMETOOLONG);
 
 	req = fuse_get_request(fc);
 	if (!req)
-		return -EINTR;
+		return ERR_PTR(-EINTR);
 
 	fuse_lookup_init(req, dir, entry, &outarg);
 	request_send(fc, req);
@@ -122,24 +125,22 @@ static int fuse_lookup_iget(struct inode
 				  &outarg.attr);
 		if (!inode) {
 			fuse_send_forget(fc, req, outarg.nodeid, 1);
-			return -ENOMEM;
+			return ERR_PTR(-ENOMEM);
 		}
 	}
 	fuse_put_request(fc, req);
 	if (err && err != -ENOENT)
-		return err;
+		return ERR_PTR(err);
 
-	if (inode) {
-		struct fuse_inode *fi = get_fuse_inode(inode);
-		entry->d_time =	time_to_jiffies(outarg.entry_valid,
-						outarg.entry_valid_nsec);
-		fi->i_time = time_to_jiffies(outarg.attr_valid,
-					     outarg.attr_valid_nsec);
+	if (inode && dir_alias(inode)) {
+		iput(inode);
+		return ERR_PTR(-EIO);
 	}
-
+	d_add(entry, inode);
 	entry->d_op = &fuse_dentry_operations;
-	*inodep = inode;
-	return 0;
+	if (inode)
+		fuse_change_timeout(entry, &outarg);
+	return NULL;
 }
 
 void fuse_invalidate_attr(struct inode *inode)
@@ -163,7 +164,6 @@ static int fuse_create_open(struct inode
 	struct fuse_open_in inarg;
 	struct fuse_open_out outopen;
 	struct fuse_entry_out outentry;
-	struct fuse_inode *fi;
 	struct fuse_file *ff;
 	struct file *file;
 	int flags = nd->intent.open.flags - 1;
@@ -224,13 +224,8 @@ static int fuse_create_open(struct inode
 		goto out_put_request;
 	}
 	fuse_put_request(fc, req);
-	entry->d_time =	time_to_jiffies(outentry.entry_valid,
-					outentry.entry_valid_nsec);
-	fi = get_fuse_inode(inode);
-	fi->i_time = time_to_jiffies(outentry.attr_valid,
-				     outentry.attr_valid_nsec);
-
 	d_instantiate(entry, inode);
+	fuse_change_timeout(entry, &outentry);
 	file = lookup_instantiate_filp(nd, entry, generic_file_open);
 	if (IS_ERR(file)) {
 		ff->fh = outopen.fh;
@@ -254,7 +249,6 @@ static int create_new_entry(struct fuse_
 {
 	struct fuse_entry_out outarg;
 	struct inode *inode;
-	struct fuse_inode *fi;
 	int err;
 
 	req->in.h.nodeid = get_node_id(dir);
@@ -286,14 +280,8 @@ static int create_new_entry(struct fuse_
 		return -EIO;
 	}
 
-	entry->d_time = time_to_jiffies(outarg.entry_valid,
-					outarg.entry_valid_nsec);
-
-	fi = get_fuse_inode(inode);
-	fi->i_time = time_to_jiffies(outarg.attr_valid,
-				     outarg.attr_valid_nsec);
-
 	d_instantiate(entry, inode);
+	fuse_change_timeout(entry, &outarg);
 	fuse_invalidate_attr(dir);
 	return 0;
 }
@@ -883,23 +871,6 @@ static int fuse_getattr(struct vfsmount 
 	return err;
 }
 
-static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
-				  struct nameidata *nd)
-{
-	struct inode *inode;
-	int err;
-
-	err = fuse_lookup_iget(dir, entry, &inode);
-	if (err)
-		return ERR_PTR(err);
-	if (inode && dir_alias(inode)) {
-		iput(inode);
-		return ERR_PTR(-EIO);
-	}
-	d_add(entry, inode);
-	return NULL;
-}
-
 static int fuse_setxattr(struct dentry *entry, const char *name,
 			 const void *value, size_t size, int flags)
 {

[PATCH 4/7] fuse: clean up page offset calculation

[Miklos Szeredi]

Use page_offset() instead of doing page offset calculation by hand.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

---
Index: linux/fs/fuse/file.c
===================================================================
--- linux.orig/fs/fuse/file.c	2005-11-28 14:01:07.000000000 +0100
+++ linux/fs/fuse/file.c	2005-11-28 14:02:07.000000000 +0100
@@ -272,7 +272,6 @@ static int fuse_readpage(struct file *fi
 {
 	struct inode *inode = page->mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
-	loff_t pos = (loff_t) page->index << PAGE_CACHE_SHIFT;
 	struct fuse_req *req = fuse_get_request(fc);
 	int err = -EINTR;
 	if (!req)
@@ -281,7 +280,7 @@ static int fuse_readpage(struct file *fi
 	req->out.page_zeroing = 1;
 	req->num_pages = 1;
 	req->pages[0] = page;
-	fuse_send_read(req, file, inode, pos, PAGE_CACHE_SIZE);
+	fuse_send_read(req, file, inode, page_offset(page), PAGE_CACHE_SIZE);
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
 	if (!err)
@@ -295,7 +294,7 @@ static int fuse_readpage(struct file *fi
 static int fuse_send_readpages(struct fuse_req *req, struct file *file,
 			       struct inode *inode)
 {
-	loff_t pos = (loff_t) req->pages[0]->index << PAGE_CACHE_SHIFT;
+	loff_t pos = page_offset(req->pages[0]);
 	size_t count = req->num_pages << PAGE_CACHE_SHIFT;
 	unsigned i;
 	req->out.page_zeroing = 1;
@@ -402,7 +401,7 @@ static int fuse_commit_write(struct file
 	unsigned count = to - offset;
 	struct inode *inode = page->mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
-	loff_t pos = ((loff_t) page->index << PAGE_CACHE_SHIFT) + offset;
+	loff_t pos = page_offset(page) + offset;
 	struct fuse_req *req = fuse_get_request(fc);
 	if (!req)
 		return -EINTR;

[PATCH 5/7] fuse: bump interface version

[Miklos Szeredi]

Change interface version to 7.4.

Following changes will need backward compatibility support, so store
the minor version returned by userspace.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

---
Index: linux/fs/fuse/dev.c
===================================================================
--- linux.orig/fs/fuse/dev.c	2005-11-22 14:45:54.000000000 +0100
+++ linux/fs/fuse/dev.c	2005-11-28 12:02:10.000000000 +0100
@@ -178,6 +178,8 @@ static void request_end(struct fuse_conn
 		if (req->misc.init_in_out.major != FUSE_KERNEL_VERSION)
 			fc->conn_error = 1;
 
+		fc->minor = req->misc.init_in_out.minor;
+
 		/* After INIT reply is received other requests can go
 		   out.  So do (FUSE_MAX_OUTSTANDING - 1) number of
 		   up()s on outstanding_sem.  The last up() is done in
Index: linux/include/linux/fuse.h
===================================================================
--- linux.orig/include/linux/fuse.h	2005-11-22 14:45:58.000000000 +0100
+++ linux/include/linux/fuse.h	2005-11-28 11:59:01.000000000 +0100
@@ -14,7 +14,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 3
+#define FUSE_KERNEL_MINOR_VERSION 4
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
Index: linux/fs/fuse/fuse_i.h
===================================================================
--- linux.orig/fs/fuse/fuse_i.h	2005-11-22 14:45:54.000000000 +0100
+++ linux/fs/fuse/fuse_i.h	2005-11-28 12:02:36.000000000 +0100
@@ -272,6 +272,9 @@ struct fuse_conn {
 	/** Is create not implemented by fs? */
 	unsigned no_create : 1;
 
+	/** Negotiated minor version */
+	unsigned minor;
+
 	/** Backing dev info */
 	struct backing_dev_info bdi;
 };

[PATCH 6/7] fuse: add frsize to statfs reply

[Miklos Szeredi]

Add 'frsize' member to the statfs reply.

I'm not sure if sending f_fsid will ever be needed, but just in case
leave some space at the end of the structure, so less compatibility
mess would be required.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

---
Index: linux/fs/fuse/inode.c
===================================================================
--- linux.orig/fs/fuse/inode.c	2005-11-28 14:01:07.000000000 +0100
+++ linux/fs/fuse/inode.c	2005-11-28 16:45:12.000000000 +0100
@@ -218,6 +218,7 @@ static void convert_fuse_statfs(struct k
 {
 	stbuf->f_type    = FUSE_SUPER_MAGIC;
 	stbuf->f_bsize   = attr->bsize;
+	stbuf->f_frsize  = attr->frsize;
 	stbuf->f_blocks  = attr->blocks;
 	stbuf->f_bfree   = attr->bfree;
 	stbuf->f_bavail  = attr->bavail;
@@ -238,10 +239,12 @@ static int fuse_statfs(struct super_bloc
 	if (!req)
 		return -EINTR;
 
+	memset(&outarg, 0, sizeof(outarg));
 	req->in.numargs = 0;
 	req->in.h.opcode = FUSE_STATFS;
 	req->out.numargs = 1;
-	req->out.args[0].size = sizeof(outarg);
+	req->out.args[0].size =
+		fc->minor < 4 ? FUSE_COMPAT_STATFS_SIZE : sizeof(outarg);
 	req->out.args[0].value = &outarg;
 	request_send(fc, req);
 	err = req->out.h.error;
Index: linux/include/linux/fuse.h
===================================================================
--- linux.orig/include/linux/fuse.h	2005-11-28 14:02:09.000000000 +0100
+++ linux/include/linux/fuse.h	2005-11-28 15:25:14.000000000 +0100
@@ -53,6 +53,9 @@ struct fuse_kstatfs {
 	__u64	ffree;
 	__u32	bsize;
 	__u32	namelen;
+	__u32	frsize;
+	__u32	padding;
+	__u32	spare[6];
 };
 
 #define FATTR_MODE	(1 << 0)
@@ -213,6 +216,8 @@ struct fuse_write_out {
 	__u32	padding;
 };
 
+#define FUSE_COMPAT_STATFS_SIZE 48
+
 struct fuse_statfs_out {
 	struct fuse_kstatfs st;
 };

[PATCH 7/7] fuse: support caching negative dentries

[Miklos Szeredi]

Add support for caching negative dentries.

Up till now, ->d_revalidate() always forced a new lookup on these.
Now let the lookup method return a zero node ID (not used for anything
else) meaning a negative entry, but with a positive cache timeout.
The old way of signaling negative entry (replying ENOENT) still works.

Userspace should check the ABI minor version to see whether sending a
zero ID is allowed by the kernel or not.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

---
Index: linux/fs/fuse/dir.c
===================================================================
--- linux.orig/fs/fuse/dir.c	2005-11-28 17:55:27.000000000 +0100
+++ linux/fs/fuse/dir.c	2005-11-28 18:07:23.000000000 +0100
@@ -23,9 +23,26 @@ static inline unsigned long time_to_jiff
 
 static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o)
 {
-	struct fuse_inode *fi = get_fuse_inode(entry->d_inode);
 	entry->d_time = time_to_jiffies(o->entry_valid, o->entry_valid_nsec);
-	fi->i_time = time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
+	if (entry->d_inode)
+		get_fuse_inode(entry->d_inode)->i_time =
+			time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
+}
+
+void fuse_invalidate_attr(struct inode *inode)
+{
+	get_fuse_inode(inode)->i_time = jiffies - 1;
+}
+
+static void fuse_invalidate_entry_cache(struct dentry *entry)
+{
+	entry->d_time = jiffies - 1;
+}
+
+static void fuse_invalidate_entry(struct dentry *entry)
+{
+	d_invalidate(entry);
+	fuse_invalidate_entry_cache(entry);
 }
 
 static void fuse_lookup_init(struct fuse_req *req, struct inode *dir,
@@ -45,15 +62,22 @@ static void fuse_lookup_init(struct fuse
 
 static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
 {
-	if (!entry->d_inode || is_bad_inode(entry->d_inode))
+	struct inode *inode = entry->d_inode;
+
+	if (inode && is_bad_inode(inode))
 		return 0;
 	else if (time_after(jiffies, entry->d_time)) {
 		int err;
 		struct fuse_entry_out outarg;
-		struct inode *inode = entry->d_inode;
-		struct fuse_inode *fi = get_fuse_inode(inode);
-		struct fuse_conn *fc = get_fuse_conn(inode);
-		struct fuse_req *req = fuse_get_request(fc);
+		struct fuse_conn *fc;
+		struct fuse_req *req;
+
+		fuse_invalidate_entry_cache(entry);
+		if (!inode)
+			return 0;
+
+		fc = get_fuse_conn(inode);
+		req = fuse_get_request(fc);
 		if (!req)
 			return 0;
 
@@ -61,6 +85,7 @@ static int fuse_dentry_revalidate(struct
 		request_send(fc, req);
 		err = req->out.h.error;
 		if (!err) {
+			struct fuse_inode *fi = get_fuse_inode(inode);
 			if (outarg.nodeid != get_node_id(inode)) {
 				fuse_send_forget(fc, req, outarg.nodeid, 1);
 				return 0;
@@ -118,9 +143,9 @@ static struct dentry *fuse_lookup(struct
 	fuse_lookup_init(req, dir, entry, &outarg);
 	request_send(fc, req);
 	err = req->out.h.error;
-	if (!err && invalid_nodeid(outarg.nodeid))
+	if (!err && outarg.nodeid && invalid_nodeid(outarg.nodeid))
 		err = -EIO;
-	if (!err) {
+	if (!err && outarg.nodeid) {
 		inode = fuse_iget(dir->i_sb, outarg.nodeid, outarg.generation,
 				  &outarg.attr);
 		if (!inode) {
@@ -138,22 +163,13 @@ static struct dentry *fuse_lookup(struct
 	}
 	d_add(entry, inode);
 	entry->d_op = &fuse_dentry_operations;
-	if (inode)
+	if (!err)
 		fuse_change_timeout(entry, &outarg);
+	else
+		fuse_invalidate_entry_cache(entry);
 	return NULL;
 }
 
-void fuse_invalidate_attr(struct inode *inode)
-{
-	get_fuse_inode(inode)->i_time = jiffies - 1;
-}
-
-static void fuse_invalidate_entry(struct dentry *entry)
-{
-	d_invalidate(entry);
-	entry->d_time = jiffies - 1;
-}
-
 static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
 			    struct nameidata *nd)
 {
@@ -387,6 +403,7 @@ static int fuse_unlink(struct inode *dir
 		inode->i_nlink = 0;
 		fuse_invalidate_attr(inode);
 		fuse_invalidate_attr(dir);
+		fuse_invalidate_entry_cache(entry);
 	} else if (err == -EINTR)
 		fuse_invalidate_entry(entry);
 	return err;
@@ -412,6 +429,7 @@ static int fuse_rmdir(struct inode *dir,
 	if (!err) {
 		entry->d_inode->i_nlink = 0;
 		fuse_invalidate_attr(dir);
+		fuse_invalidate_entry_cache(entry);
 	} else if (err == -EINTR)
 		fuse_invalidate_entry(entry);
 	return err;
@@ -447,6 +465,10 @@ static int fuse_rename(struct inode *old
 		fuse_invalidate_attr(olddir);
 		if (olddir != newdir)
 			fuse_invalidate_attr(newdir);
+
+		/* newent will end up negative */
+		if (newent->d_inode)
+			fuse_invalidate_entry_cache(newent);
 	} else if (err == -EINTR) {
 		/* If request was interrupted, DEITY only knows if the
 		   rename actually took place.  If the invalidation

Re: [PATCH 7/7] fuse: support caching negative dentries

[Andrew Morton]

Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> +void fuse_invalidate_attr(struct inode *inode)
>  +{
>  +	get_fuse_inode(inode)->i_time = jiffies - 1;
>  +}
>  +
>  +static void fuse_invalidate_entry_cache(struct dentry *entry)
>  +{
>  +	entry->d_time = jiffies - 1;
>  +}
>  +

I'd normally have a little whine about lack of comments here - pity the
poor programmer who is trying to work out why on earth that code is doing
that.

But fuse is pretty much a comment-free zone anyway.  Please don't go near
any buses.  

Re: [PATCH 7/7] fuse: support caching negative dentries

[Miklos Szeredi]

> >
> > +void fuse_invalidate_attr(struct inode *inode)
> >  +{
> >  +	get_fuse_inode(inode)->i_time = jiffies - 1;
> >  +}
> >  +
> >  +static void fuse_invalidate_entry_cache(struct dentry *entry)
> >  +{
> >  +	entry->d_time = jiffies - 1;
> >  +}
> >  +
> 
> I'd normally have a little whine about lack of comments here - pity the
> poor programmer who is trying to work out why on earth that code is doing
> that.

Well, I thought it was evident, but it seems not.  I'll add some
comments.

> But fuse is pretty much a comment-free zone anyway.

I think most of FUSE is really-really obvious.  The most complex parts
are in the device handling, which is now quite well commented (thanks
to your earlier whining :).

> Please don't go near any buses.

Don't worry, I usually go by tram.

Miklos

Re: [PATCH 1/7] fuse: check directory aliasing in mkdir

[Trond Myklebust]

On Mon, 2005-11-28 at 20:43 +0100, Miklos Szeredi wrote:
> Check the created directory inode for aliases in the mkdir() method.


Can't you use d_add_unique() here?

Cheers,
  Trond

> Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
> 
> ---
> Index: linux/fs/fuse/dir.c
> ===================================================================
> --- linux.orig/fs/fuse/dir.c	2005-11-28 14:01:08.000000000 +0100
> +++ linux/fs/fuse/dir.c	2005-11-28 14:01:52.000000000 +0100
> @@ -74,6 +74,19 @@ static int fuse_dentry_revalidate(struct
>  	return 1;
>  }
>  
> +static int dir_alias(struct inode *inode)
> +{
> +	if (S_ISDIR(inode->i_mode)) {
> +		/* Don't allow creating an alias to a directory  */
> +		struct dentry *alias = d_find_alias(inode);
> +		if (alias) {
> +			dput(alias);
> +			return 1;
> +		}
> +	}
> +	return 0;
> +}
> +
>  static struct dentry_operations fuse_dentry_operations = {
>  	.d_revalidate	= fuse_dentry_revalidate,
>  };
> @@ -263,7 +276,7 @@ static int create_new_entry(struct fuse_
>  	fuse_put_request(fc, req);
>  
>  	/* Don't allow userspace to do really stupid things... */
> -	if ((inode->i_mode ^ mode) & S_IFMT) {
> +	if (((inode->i_mode ^ mode) & S_IFMT) || dir_alias(inode)) {
>  		iput(inode);
>  		return -EIO;
>  	}
> @@ -874,14 +887,9 @@ static struct dentry *fuse_lookup(struct
>  	err = fuse_lookup_iget(dir, entry, &inode);
>  	if (err)
>  		return ERR_PTR(err);
> -	if (inode && S_ISDIR(inode->i_mode)) {
> -		/* Don't allow creating an alias to a directory  */
> -		struct dentry *alias = d_find_alias(inode);
> -		if (alias) {
> -			dput(alias);
> -			iput(inode);
> -			return ERR_PTR(-EIO);
> -		}
> +	if (inode && dir_alias(inode)) {
> +		iput(inode);
> +		return ERR_PTR(-EIO);
>  	}
>  	d_add(entry, inode);
>  	return NULL;
> -
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Re: [PATCH 1/7] fuse: check directory aliasing in mkdir

[Miklos Szeredi]

> > Check the created directory inode for aliases in the mkdir() method.
> 
> 
> Can't you use d_add_unique() here?

The patch is checking for hashed aliases of an inode.  E.g. if /foo is
a directory and has a ID of 28, and mkdir /bar returns the same ID,
then the mkdir should fail.

It's an illegal for the filesystem to create two directories refering
to the same inode.

OTOH d_add_unique() is looking for unhashed aliases to resurrect,
which may or may not make sense in fuse.  I'll think about it a bit
more.

Thanks,
Miklos