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fuse: use d_materialise_unique()

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Use d_materialise_unique() instead of d_splice_alias().  This allows dentry
subtrees to be moved to a new place if there moved, even if something is
referencing a dentry in the subtree (open fd, cwd, etc..).

This will also allow us to drop a subtree if it is found to be replaced by
something else.  In this case the disconnected subtree can later be
reconnected to its new location.

d_materialise_unique() ensures that a directory entry only ever has one
alias.  We keep fc->inst_mutex around the calls for d_materialise_unique()
on directories to prevent a race with mkdir "stealing" the inode.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Miklos Szeredi 2013-09-05 11:44:42 +02:00 committed by Al Viro
parent 6497d160f6
commit 5835f3390e
1 changed files with 26 additions and 43 deletions
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69
fs/fuse/dir.c
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@ -267,26 +267,6 @@ int fuse_valid_type(int m)
S_ISBLK(m) || S_ISFIFO(m) || S_ISSOCK(m);
}
/*
* Add a directory inode to a dentry, ensuring that no other dentry
* refers to this inode. Called with fc->inst_mutex.
*/
static struct dentry *fuse_d_add_directory(struct dentry *entry,
struct inode *inode)
{
struct dentry *alias = d_find_alias(inode);
if (alias && !(alias->d_flags & DCACHE_DISCONNECTED)) {
/* This tries to shrink the subtree below alias */
fuse_invalidate_entry(alias);
dput(alias);
if (!hlist_empty(&inode->i_dentry))
return ERR_PTR(-EBUSY);
} else {
dput(alias);
}
return d_splice_alias(inode, entry);
}
int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
struct fuse_entry_out *outarg, struct inode **inode)
{
@ -345,6 +325,24 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
return err;
}
static struct dentry *fuse_materialise_dentry(struct dentry *dentry,
struct inode *inode)
{
struct dentry *newent;
if (inode && S_ISDIR(inode->i_mode)) {
struct fuse_conn *fc = get_fuse_conn(inode);
mutex_lock(&fc->inst_mutex);
newent = d_materialise_unique(dentry, inode);
mutex_unlock(&fc->inst_mutex);
} else {
newent = d_materialise_unique(dentry, inode);
}
return newent;
}
static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
unsigned int flags)
{
@ -352,7 +350,6 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
struct fuse_entry_out outarg;
struct inode *inode;
struct dentry *newent;
struct fuse_conn *fc = get_fuse_conn(dir);
bool outarg_valid = true;
err = fuse_lookup_name(dir->i_sb, get_node_id(dir), &entry->d_name,
@ -368,16 +365,10 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
if (inode && get_node_id(inode) == FUSE_ROOT_ID)
goto out_iput;
if (inode && S_ISDIR(inode->i_mode)) {
mutex_lock(&fc->inst_mutex);
newent = fuse_d_add_directory(entry, inode);
mutex_unlock(&fc->inst_mutex);
err = PTR_ERR(newent);
if (IS_ERR(newent))
goto out_iput;
} else {
newent = d_splice_alias(inode, entry);
}
newent = fuse_materialise_dentry(entry, inode);
err = PTR_ERR(newent);
if (IS_ERR(newent))
goto out_err;
entry = newent ? newent : entry;
if (outarg_valid)
@ -1275,18 +1266,10 @@ static int fuse_direntplus_link(struct file *file,
if (!inode)
goto out;
if (S_ISDIR(inode->i_mode)) {
mutex_lock(&fc->inst_mutex);
alias = fuse_d_add_directory(dentry, inode);
mutex_unlock(&fc->inst_mutex);
err = PTR_ERR(alias);
if (IS_ERR(alias)) {
iput(inode);
goto out;
}
} else {
alias = d_splice_alias(inode, dentry);
}
alias = fuse_materialise_dentry(dentry, inode);
err = PTR_ERR(alias);
if (IS_ERR(alias))
goto out;
if (alias) {
dput(dentry);