vfs: add d_walk()
This one replaces three instances open coded tree walking (have_submounts, select_parent, d_genocide) with a common helper. In addition to slightly reducing the kernel size, this simplifies the callers and makes them less bug prone. 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
Al Viro
parent
01ddc4ede5
commit
db14fc3abc
315
fs/dcache.c
315
fs/dcache.c
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@ -1031,34 +1031,56 @@ static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq
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return new;
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}
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/*
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* Search for at least 1 mount point in the dentry's subdirs.
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* We descend to the next level whenever the d_subdirs
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* list is non-empty and continue searching.
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*/
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/**
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* have_submounts - check for mounts over a dentry
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* @parent: dentry to check.
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*
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* Return true if the parent or its subdirectories contain
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* a mount point
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* enum d_walk_ret - action to talke during tree walk
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* @D_WALK_CONTINUE: contrinue walk
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* @D_WALK_QUIT: quit walk
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* @D_WALK_NORETRY: quit when retry is needed
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* @D_WALK_SKIP: skip this dentry and its children
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*/
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int have_submounts(struct dentry *parent)
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enum d_walk_ret {
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D_WALK_CONTINUE,
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D_WALK_QUIT,
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D_WALK_NORETRY,
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D_WALK_SKIP,
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};
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/**
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* d_walk - walk the dentry tree
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* @parent: start of walk
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* @data: data passed to @enter() and @finish()
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* @enter: callback when first entering the dentry
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* @finish: callback when successfully finished the walk
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*
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* The @enter() and @finish() callbacks are called with d_lock held.
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*/
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static void d_walk(struct dentry *parent, void *data,
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enum d_walk_ret (*enter)(void *, struct dentry *),
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void (*finish)(void *))
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{
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struct dentry *this_parent;
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struct list_head *next;
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unsigned seq;
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int locked = 0;
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enum d_walk_ret ret;
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bool retry = true;
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seq = read_seqbegin(&rename_lock);
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again:
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this_parent = parent;
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if (d_mountpoint(parent))
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goto positive;
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spin_lock(&this_parent->d_lock);
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ret = enter(data, this_parent);
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switch (ret) {
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case D_WALK_CONTINUE:
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break;
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case D_WALK_QUIT:
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case D_WALK_SKIP:
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goto out_unlock;
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case D_WALK_NORETRY:
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retry = false;
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break;
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}
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repeat:
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next = this_parent->d_subdirs.next;
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resume:
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@ -1068,12 +1090,22 @@ resume:
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next = tmp->next;
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spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
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/* Have we found a mount point ? */
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if (d_mountpoint(dentry)) {
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ret = enter(data, dentry);
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switch (ret) {
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case D_WALK_CONTINUE:
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break;
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case D_WALK_QUIT:
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spin_unlock(&dentry->d_lock);
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spin_unlock(&this_parent->d_lock);
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goto positive;
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goto out_unlock;
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case D_WALK_NORETRY:
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retry = false;
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break;
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case D_WALK_SKIP:
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spin_unlock(&dentry->d_lock);
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continue;
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}
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if (!list_empty(&dentry->d_subdirs)) {
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spin_unlock(&this_parent->d_lock);
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spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
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@ -1094,26 +1126,61 @@ resume:
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next = child->d_u.d_child.next;
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goto resume;
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}
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if (!locked && read_seqretry(&rename_lock, seq)) {
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spin_unlock(&this_parent->d_lock);
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goto rename_retry;
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}
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if (finish)
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finish(data);
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out_unlock:
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spin_unlock(&this_parent->d_lock);
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if (!locked && read_seqretry(&rename_lock, seq))
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goto rename_retry;
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if (locked)
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write_sequnlock(&rename_lock);
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return 0; /* No mount points found in tree */
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positive:
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if (!locked && read_seqretry(&rename_lock, seq))
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goto rename_retry;
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if (locked)
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write_sequnlock(&rename_lock);
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return 1;
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return;
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rename_retry:
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if (!retry)
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return;
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if (locked)
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goto again;
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locked = 1;
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write_seqlock(&rename_lock);
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goto again;
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}
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/*
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* Search for at least 1 mount point in the dentry's subdirs.
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* We descend to the next level whenever the d_subdirs
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* list is non-empty and continue searching.
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*/
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/**
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* have_submounts - check for mounts over a dentry
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* @parent: dentry to check.
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*
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* Return true if the parent or its subdirectories contain
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* a mount point
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*/
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static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
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{
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int *ret = data;
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if (d_mountpoint(dentry)) {
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*ret = 1;
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return D_WALK_QUIT;
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}
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return D_WALK_CONTINUE;
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}
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int have_submounts(struct dentry *parent)
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{
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int ret = 0;
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d_walk(parent, &ret, check_mount, NULL);
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return ret;
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}
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EXPORT_SYMBOL(have_submounts);
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/*
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@ -1130,93 +1197,46 @@ EXPORT_SYMBOL(have_submounts);
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* drop the lock and return early due to latency
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* constraints.
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*/
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static int select_parent(struct dentry *parent, struct list_head *dispose)
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struct select_data {
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struct dentry *start;
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struct list_head dispose;
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int found;
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};
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static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
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{
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struct dentry *this_parent;
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struct list_head *next;
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unsigned seq;
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int found = 0;
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int locked = 0;
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struct select_data *data = _data;
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enum d_walk_ret ret = D_WALK_CONTINUE;
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seq = read_seqbegin(&rename_lock);
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again:
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this_parent = parent;
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spin_lock(&this_parent->d_lock);
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repeat:
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next = this_parent->d_subdirs.next;
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resume:
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while (next != &this_parent->d_subdirs) {
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struct list_head *tmp = next;
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struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
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next = tmp->next;
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if (data->start == dentry)
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goto out;
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spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
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/*
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* move only zero ref count dentries to the dispose list.
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*
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* Those which are presently on the shrink list, being processed
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* by shrink_dentry_list(), shouldn't be moved. Otherwise the
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* loop in shrink_dcache_parent() might not make any progress
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* and loop forever.
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*/
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if (dentry->d_lockref.count) {
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dentry_lru_del(dentry);
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} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
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dentry_lru_move_list(dentry, dispose);
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dentry->d_flags |= DCACHE_SHRINK_LIST;
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found++;
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}
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/*
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* We can return to the caller if we have found some (this
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* ensures forward progress). We'll be coming back to find
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* the rest.
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*/
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if (found && need_resched()) {
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spin_unlock(&dentry->d_lock);
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goto out;
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}
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/*
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* Descend a level if the d_subdirs list is non-empty.
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*/
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if (!list_empty(&dentry->d_subdirs)) {
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spin_unlock(&this_parent->d_lock);
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spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
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this_parent = dentry;
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spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
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goto repeat;
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}
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spin_unlock(&dentry->d_lock);
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/*
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* move only zero ref count dentries to the dispose list.
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*
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* Those which are presently on the shrink list, being processed
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* by shrink_dentry_list(), shouldn't be moved. Otherwise the
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* loop in shrink_dcache_parent() might not make any progress
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* and loop forever.
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*/
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if (dentry->d_lockref.count) {
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dentry_lru_del(dentry);
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} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
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dentry_lru_move_list(dentry, &data->dispose);
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dentry->d_flags |= DCACHE_SHRINK_LIST;
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data->found++;
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ret = D_WALK_NORETRY;
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}
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/*
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* All done at this level ... ascend and resume the search.
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* We can return to the caller if we have found some (this
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* ensures forward progress). We'll be coming back to find
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* the rest.
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*/
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if (this_parent != parent) {
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struct dentry *child = this_parent;
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this_parent = try_to_ascend(this_parent, locked, seq);
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if (!this_parent)
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goto rename_retry;
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next = child->d_u.d_child.next;
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goto resume;
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}
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if (data->found && need_resched())
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ret = D_WALK_QUIT;
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out:
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spin_unlock(&this_parent->d_lock);
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if (!locked && read_seqretry(&rename_lock, seq))
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goto rename_retry;
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if (locked)
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write_sequnlock(&rename_lock);
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return found;
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rename_retry:
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if (found)
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return found;
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if (locked)
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goto again;
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locked = 1;
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write_seqlock(&rename_lock);
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goto again;
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return ret;
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}
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/**
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@ -1225,13 +1245,20 @@ rename_retry:
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*
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* Prune the dcache to remove unused children of the parent dentry.
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*/
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void shrink_dcache_parent(struct dentry * parent)
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void shrink_dcache_parent(struct dentry *parent)
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{
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LIST_HEAD(dispose);
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int found;
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for (;;) {
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struct select_data data;
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while ((found = select_parent(parent, &dispose)) != 0) {
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shrink_dentry_list(&dispose);
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INIT_LIST_HEAD(&data.dispose);
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data.start = parent;
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data.found = 0;
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d_walk(parent, &data, select_collect, NULL);
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if (!data.found)
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break;
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shrink_dentry_list(&data.dispose);
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cond_resched();
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}
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}
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@ -2928,64 +2955,24 @@ int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
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return result;
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}
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void d_genocide(struct dentry *root)
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static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
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{
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struct dentry *this_parent;
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struct list_head *next;
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unsigned seq;
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int locked = 0;
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struct dentry *root = data;
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if (dentry != root) {
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if (d_unhashed(dentry) || !dentry->d_inode)
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return D_WALK_SKIP;
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seq = read_seqbegin(&rename_lock);
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again:
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this_parent = root;
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spin_lock(&this_parent->d_lock);
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repeat:
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next = this_parent->d_subdirs.next;
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resume:
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while (next != &this_parent->d_subdirs) {
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struct list_head *tmp = next;
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struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
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next = tmp->next;
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spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
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if (d_unhashed(dentry) || !dentry->d_inode) {
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spin_unlock(&dentry->d_lock);
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continue;
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}
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if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
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dentry->d_flags |= DCACHE_GENOCIDE;
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dentry->d_lockref.count--;
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}
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if (!list_empty(&dentry->d_subdirs)) {
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spin_unlock(&this_parent->d_lock);
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spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
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this_parent = dentry;
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spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
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goto repeat;
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}
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spin_unlock(&dentry->d_lock);
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}
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if (this_parent != root) {
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struct dentry *child = this_parent;
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this_parent = try_to_ascend(this_parent, locked, seq);
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if (!this_parent)
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goto rename_retry;
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next = child->d_u.d_child.next;
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goto resume;
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}
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spin_unlock(&this_parent->d_lock);
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if (!locked && read_seqretry(&rename_lock, seq))
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goto rename_retry;
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if (locked)
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write_sequnlock(&rename_lock);
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return;
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return D_WALK_CONTINUE;
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}
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rename_retry:
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if (locked)
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goto again;
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locked = 1;
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write_seqlock(&rename_lock);
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goto again;
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void d_genocide(struct dentry *parent)
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{
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d_walk(parent, parent, d_genocide_kill, NULL);
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}
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void d_tmpfile(struct dentry *dentry, struct inode *inode)
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