Commit 451d0f59 authored by John Muir's avatar John Muir Committed by Miklos Szeredi
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FUSE: Notifying the kernel of deletion.



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.

The current 'fuse_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 'fuse_notify_inval_entry' is used to notify of a deleted directory is
avoided when 'fuse_notify_delete' is used instead.

The following scenario demonstrates the difference:
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 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 the 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 'fuse_notify_delete' function, then the above
ls will find the new directory as expected.
Signed-off-by: default avatarJohn Muir <john@jmuir.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent b18da0c5
......@@ -1378,7 +1378,59 @@ static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
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;
......@@ -1597,6 +1649,9 @@ static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
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;
......
......@@ -868,7 +868,7 @@ int fuse_update_attributes(struct inode *inode, struct kstat *stat,
}
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 super_block *sb, u64 parent_nodeid,
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);
......
......@@ -755,9 +755,15 @@ int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid,
/**
* 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);
......
......@@ -53,6 +53,7 @@
*
* 7.18
* - add FUSE_IOCTL_DIR flag
* - add FUSE_NOTIFY_DELETE
*/
#ifndef _LINUX_FUSE_H
......@@ -288,6 +289,7 @@ 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,
};
......@@ -611,6 +613,13 @@ struct fuse_notify_inval_entry_out {
__u32 padding;
};
struct fuse_notify_delete_out {
__u64 parent;
__u64 child;
__u32 namelen;
__u32 padding;
};
struct fuse_notify_store_out {
__u64 nodeid;
__u64 offset;
......
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