From: Miklos Szeredi <mszeredi@xxxxxxx>
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@xxxxxxx>
---
fs/fuse/dir.c | 69 ++++++++++++++++++++++-------------------------------------
1 file changed, 26 insertions(+), 43 deletions(-)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 72a5d5b..131d14b 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -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);
--
1.8.1.4
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