Allows a FUSE file-system to tell the kernel when a file or directory is deleted. If the specified dentry has the specified inode number, the kernel will unhash it.
Signed-off-by: John Muir <john@xxxxxxxxx>
---
Please find below a patch that add notification of deletion to the FUSE kernel interface. These patches allow the file-system to tell the kernel when a file (and more particularly) a directory is deleted. This is needed because using the current 'notify_inval_entry' does not cause the kernel to clean up directories that are in use properly, and as a result the users of those directories see incorrect semantics from the file-system. The error condition seen when 'notify_inval_entry' is used to notify of a deleted directory is avoided when 'notify_delete' is used instead.
I'll demonstrate below with the following scenario:
1. User A chdirs into 'testdir' and starts reading 'testfile'.
2. User B rm -rf 'testdir'.
3. User B creates 'testdir'.
4. User C chdirs into 'testdir'.
If you run the above within the same machine on any file-system (including fuse file-systems), there is no problem: user C is able to chdir into the new testdir. The old testdir is removed from the dentry tree, but still open by user A.
If, on the other hand, the operations 2 and 3 are performed via the network such that the fuse file-system uses one of the notify functions to tell the kernel that the nodes are gone, then the following error occurs for user C while user A holds the original directory open:
muirj@empacher:~> ls /test/testdir
ls: cannot access /test/testdir: No such file or directory
The issue here is that the kernel still has a dentry for testdir, and so it is requesting the attributes for the old directory, while my file-system is responding that the directory no longer exists.
If on the other hand, if the file-system can notify the kernel that the directory is deleted using the new 'notify_delete' function, then the above ls will find the new directory as expected.
diff -updr orig/fs/fuse/dev.c new/fs/fuse/dev.c
--- orig/fs/fuse/dev.c 2011-12-01 23:56:01.000000000 +0100
+++ new/fs/fuse/dev.c 2011-12-06 19:30:50.682000123 +0100
@@ -1378,7 +1378,59 @@ static int fuse_notify_inval_entry(struc
down_read(&fc->killsb);
err = -ENOENT;
if (fc->sb)
- err = fuse_reverse_inval_entry(fc->sb, outarg.parent, &name);
+ err = fuse_reverse_inval_entry(fc->sb, outarg.parent, 0, &name);
+ up_read(&fc->killsb);
+ kfree(buf);
+ return err;
+
+err:
+ kfree(buf);
+ fuse_copy_finish(cs);
+ return err;
+}
+
+static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size,
+ struct fuse_copy_state *cs)
+{
+ struct fuse_notify_delete_out outarg;
+ int err = -ENOMEM;
+ char *buf;
+ struct qstr name;
+
+ buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
+ if (!buf)
+ goto err;
+
+ err = -EINVAL;
+ if (size < sizeof(outarg))
+ goto err;
+
+ err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+ if (err)
+ goto err;
+
+ err = -ENAMETOOLONG;
+ if (outarg.namelen > FUSE_NAME_MAX)
+ goto err;
+
+ err = -EINVAL;
+ if (size != sizeof(outarg) + outarg.namelen + 1)
+ goto err;
+
+ name.name = buf;
+ name.len = outarg.namelen;
+ err = fuse_copy_one(cs, buf, outarg.namelen + 1);
+ if (err)
+ goto err;
+ fuse_copy_finish(cs);
+ buf[outarg.namelen] = 0;
+ name.hash = full_name_hash(name.name, name.len);
+
+ down_read(&fc->killsb);
+ err = -ENOENT;
+ if (fc->sb)
+ err = fuse_reverse_inval_entry(fc->sb, outarg.parent,
+ outarg.child, &name);
up_read(&fc->killsb);
kfree(buf);
return err;
@@ -1596,6 +1648,9 @@ static int fuse_notify(struct fuse_conn
case FUSE_NOTIFY_RETRIEVE:
return fuse_notify_retrieve(fc, size, cs);
+ case FUSE_NOTIFY_DELETE:
+ return fuse_notify_delete(fc, size, cs);
+
default:
fuse_copy_finish(cs);
return -EINVAL;
diff -updr orig/fs/fuse/dir.c new/fs/fuse/dir.c
--- orig/fs/fuse/dir.c 2011-12-01 23:56:01.000000000 +0100
+++ new/fs/fuse/dir.c 2011-12-06 19:30:50.683000127 +0100
@@ -868,7 +868,7 @@ int fuse_update_attributes(struct inode
}
int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,
- struct qstr *name)
+ u64 child_nodeid, struct qstr *name)
{
int err = -ENOTDIR;
struct inode *parent;
@@ -895,8 +895,36 @@ int fuse_reverse_inval_entry(struct supe
fuse_invalidate_attr(parent);
fuse_invalidate_entry(entry);
+
+ if (child_nodeid != 0 && entry->d_inode) {
+ mutex_lock(&entry->d_inode->i_mutex);
+ if (get_node_id(entry->d_inode) != child_nodeid) {
+ err = -ENOENT;
+ goto badentry;
+ }
+ if (d_mountpoint(entry)) {
+ err = -EBUSY;
+ goto badentry;
+ }
+ if (S_ISDIR(entry->d_inode->i_mode)) {
+ shrink_dcache_parent(entry);
+ if (!simple_empty(entry)) {
+ err = -ENOTEMPTY;
+ goto badentry;
+ }
+ entry->d_inode->i_flags |= S_DEAD;
+ }
+ dont_mount(entry);
+ clear_nlink(entry->d_inode);
+ err = 0;
+ badentry:
+ mutex_unlock(&entry->d_inode->i_mutex);
+ if (!err)
+ d_delete(entry);
+ } else {
+ err = 0;
+ }
dput(entry);
- err = 0;
unlock:
mutex_unlock(&parent->i_mutex);
diff -updr orig/fs/fuse/fuse_i.h new/fs/fuse/fuse_i.h
--- orig/fs/fuse/fuse_i.h 2011-12-01 23:56:01.000000000 +0100
+++ new/fs/fuse/fuse_i.h 2011-12-06 19:30:50.691000142 +0100
@@ -755,9 +755,15 @@ int fuse_reverse_inval_inode(struct supe
/**
* File-system tells the kernel to invalidate parent attributes and
* the dentry matching parent/name.
+ *
+ * If the child_nodeid is non-zero and:
+ * - matches the inode number for the dentry matching parent/name,
+ * - is not a mount point
+ * - is a file or oan empty directory
+ * then the dentry is unhashed (d_delete()).
*/
int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,
- struct qstr *name);
+ u64 child_nodeid, struct qstr *name);
int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
bool isdir);
diff -updr orig/include/linux/fuse.h new/include/linux/fuse.h
--- orig/include/linux/fuse.h 2011-12-01 23:56:01.000000000 +0100
+++ new/include/linux/fuse.h 2011-12-06 19:31:05.686000162 +0100
@@ -283,6 +283,7 @@ enum fuse_notify_code {
FUSE_NOTIFY_INVAL_ENTRY = 3,
FUSE_NOTIFY_STORE = 4,
FUSE_NOTIFY_RETRIEVE = 5,
+ FUSE_NOTIFY_DELETE = 6,
FUSE_NOTIFY_CODE_MAX,
};
@@ -605,6 +606,13 @@ struct fuse_notify_inval_entry_out {
__u32 namelen;
__u32 padding;
};
+
+struct fuse_notify_delete_out {
+ __u64 parent;
+ __u64 child;
+ __u32 namelen;
+ __u32 padding;
+};
struct fuse_notify_store_out {
__u64 nodeid;
--
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