fix loop checks in d_materialise_unique()
Both __d_unalias() and __d_materialise_dentry() need loop prevention. Grab rename_lock in caller, check for loops there... As a side benefit, we have dentry_lock_for_move() called only under rename_lock, which seriously reduces deadlock potential of the execrable "locking order" used for ->d_lock. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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parent
94c0d4ecbe
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1836750115
51
fs/dcache.c
51
fs/dcache.c
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@ -2213,14 +2213,15 @@ static void dentry_unlock_parents_for_move(struct dentry *dentry,
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* The hash value has to match the hash queue that the dentry is on..
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*/
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/*
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* d_move - move a dentry
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* __d_move - move a dentry
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* @dentry: entry to move
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* @target: new dentry
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*
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* Update the dcache to reflect the move of a file name. Negative
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* dcache entries should not be moved in this way.
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* dcache entries should not be moved in this way. Caller hold
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* rename_lock.
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*/
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void d_move(struct dentry * dentry, struct dentry * target)
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static void __d_move(struct dentry * dentry, struct dentry * target)
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{
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if (!dentry->d_inode)
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printk(KERN_WARNING "VFS: moving negative dcache entry\n");
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@ -2228,8 +2229,6 @@ void d_move(struct dentry * dentry, struct dentry * target)
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BUG_ON(d_ancestor(dentry, target));
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BUG_ON(d_ancestor(target, dentry));
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write_seqlock(&rename_lock);
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dentry_lock_for_move(dentry, target);
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write_seqcount_begin(&dentry->d_seq);
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@ -2275,6 +2274,20 @@ void d_move(struct dentry * dentry, struct dentry * target)
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spin_unlock(&target->d_lock);
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fsnotify_d_move(dentry);
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spin_unlock(&dentry->d_lock);
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}
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/*
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* d_move - move a dentry
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* @dentry: entry to move
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* @target: new dentry
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*
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* Update the dcache to reflect the move of a file name. Negative
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* dcache entries should not be moved in this way.
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*/
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void d_move(struct dentry *dentry, struct dentry *target)
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{
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write_seqlock(&rename_lock);
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__d_move(dentry, target);
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write_sequnlock(&rename_lock);
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}
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EXPORT_SYMBOL(d_move);
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@ -2302,7 +2315,7 @@ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
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* This helper attempts to cope with remotely renamed directories
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*
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* It assumes that the caller is already holding
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* dentry->d_parent->d_inode->i_mutex and the inode->i_lock
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* dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
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*
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* Note: If ever the locking in lock_rename() changes, then please
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* remember to update this too...
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@ -2317,11 +2330,6 @@ static struct dentry *__d_unalias(struct inode *inode,
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if (alias->d_parent == dentry->d_parent)
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goto out_unalias;
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/* Check for loops */
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ret = ERR_PTR(-ELOOP);
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if (d_ancestor(alias, dentry))
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goto out_err;
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/* See lock_rename() */
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ret = ERR_PTR(-EBUSY);
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if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
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@ -2331,7 +2339,7 @@ static struct dentry *__d_unalias(struct inode *inode,
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goto out_err;
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m2 = &alias->d_parent->d_inode->i_mutex;
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out_unalias:
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d_move(alias, dentry);
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__d_move(alias, dentry);
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ret = alias;
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out_err:
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spin_unlock(&inode->i_lock);
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@ -2416,15 +2424,24 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
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alias = __d_find_alias(inode, 0);
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if (alias) {
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actual = alias;
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/* Is this an anonymous mountpoint that we could splice
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* into our tree? */
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if (IS_ROOT(alias)) {
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write_seqlock(&rename_lock);
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if (d_ancestor(alias, dentry)) {
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/* Check for loops */
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actual = ERR_PTR(-ELOOP);
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} else if (IS_ROOT(alias)) {
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/* Is this an anonymous mountpoint that we
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* could splice into our tree? */
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__d_materialise_dentry(dentry, alias);
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write_sequnlock(&rename_lock);
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__d_drop(alias);
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goto found;
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}
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/* Nope, but we must(!) avoid directory aliasing */
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} else {
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/* Nope, but we must(!) avoid directory
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* aliasing */
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actual = __d_unalias(inode, dentry, alias);
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}
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write_sequnlock(&rename_lock);
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if (IS_ERR(actual))
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dput(alias);
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goto out_nolock;
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