/**
* read_seqbegin_or_lock - begin a sequence number check or locking block
- * lock: sequence lock
- * seq : sequence number to be checked
+ * @lock: sequence lock
+ * @seq : sequence number to be checked
*
* First try it once optimistically without taking the lock. If that fails,
* take the lock. The sequence number is also used as a marker for deciding
if (!(*seq & 1)) /* Even */
*seq = read_seqbegin(lock);
else /* Odd */
- write_seqlock(lock);
+ read_seqlock_excl(lock);
}
static inline int need_seqretry(seqlock_t *lock, int seq)
static inline void done_seqretry(seqlock_t *lock, int seq)
{
if (seq & 1)
- write_sequnlock(lock);
+ read_sequnlock_excl(lock);
}
/*
iput(inode);
}
+/*
+ * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
+ * is in use - which includes both the "real" per-superblock
+ * LRU list _and_ the DCACHE_SHRINK_LIST use.
+ *
+ * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
+ * on the shrink list (ie not on the superblock LRU list).
+ *
+ * The per-cpu "nr_dentry_unused" counters are updated with
+ * the DCACHE_LRU_LIST bit.
+ *
+ * These helper functions make sure we always follow the
+ * rules. d_lock must be held by the caller.
+ */
+#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
+static void d_lru_add(struct dentry *dentry)
+{
+ D_FLAG_VERIFY(dentry, 0);
+ dentry->d_flags |= DCACHE_LRU_LIST;
+ this_cpu_inc(nr_dentry_unused);
+ WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
+}
+
+static void d_lru_del(struct dentry *dentry)
+{
+ D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
+ dentry->d_flags &= ~DCACHE_LRU_LIST;
+ this_cpu_dec(nr_dentry_unused);
+ WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
+}
+
+static void d_shrink_del(struct dentry *dentry)
+{
+ D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
+ list_del_init(&dentry->d_lru);
+ dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
+ this_cpu_dec(nr_dentry_unused);
+}
+
+static void d_shrink_add(struct dentry *dentry, struct list_head *list)
+{
+ D_FLAG_VERIFY(dentry, 0);
+ list_add(&dentry->d_lru, list);
+ dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
+ this_cpu_inc(nr_dentry_unused);
+}
+
+/*
+ * These can only be called under the global LRU lock, ie during the
+ * callback for freeing the LRU list. "isolate" removes it from the
+ * LRU lists entirely, while shrink_move moves it to the indicated
+ * private list.
+ */
+static void d_lru_isolate(struct dentry *dentry)
+{
+ D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
+ dentry->d_flags &= ~DCACHE_LRU_LIST;
+ this_cpu_dec(nr_dentry_unused);
+ list_del_init(&dentry->d_lru);
+}
+
+static void d_lru_shrink_move(struct dentry *dentry, struct list_head *list)
+{
+ D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
+ dentry->d_flags |= DCACHE_SHRINK_LIST;
+ list_move_tail(&dentry->d_lru, list);
+}
+
/*
* dentry_lru_(add|del)_list) must be called with d_lock held.
*/
static void dentry_lru_add(struct dentry *dentry)
{
- if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) {
- if (list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
- this_cpu_inc(nr_dentry_unused);
- dentry->d_flags |= DCACHE_LRU_LIST;
- }
+ if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
+ d_lru_add(dentry);
}
/*
*/
static void dentry_lru_del(struct dentry *dentry)
{
- if (dentry->d_flags & DCACHE_SHRINK_LIST) {
- list_del_init(&dentry->d_lru);
- dentry->d_flags &= ~DCACHE_SHRINK_LIST;
- return;
+ if (dentry->d_flags & DCACHE_LRU_LIST) {
+ if (dentry->d_flags & DCACHE_SHRINK_LIST)
+ return d_shrink_del(dentry);
+ d_lru_del(dentry);
}
-
- if (list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
- this_cpu_dec(nr_dentry_unused);
- dentry->d_flags &= ~DCACHE_LRU_LIST;
}
/**
dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
if (&dentry->d_lru == list)
break; /* empty */
+
+ /*
+ * Get the dentry lock, and re-verify that the dentry is
+ * this on the shrinking list. If it is, we know that
+ * DCACHE_SHRINK_LIST and DCACHE_LRU_LIST are set.
+ */
spin_lock(&dentry->d_lock);
if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
spin_unlock(&dentry->d_lock);
* to the LRU here, so we can simply remove it from the list
* here regardless of whether it is referenced or not.
*/
- list_del_init(&dentry->d_lru);
- dentry->d_flags &= ~DCACHE_SHRINK_LIST;
+ d_shrink_del(dentry);
/*
* We found an inuse dentry which was not removed from
}
rcu_read_unlock();
+ /*
+ * If 'try_to_prune()' returns a dentry, it will
+ * be the same one we passed in, and d_lock will
+ * have been held the whole time, so it will not
+ * have been added to any other lists. We failed
+ * to get the inode lock.
+ *
+ * We just add it back to the shrink list.
+ */
dentry = try_prune_one_dentry(dentry);
rcu_read_lock();
if (dentry) {
- dentry->d_flags |= DCACHE_SHRINK_LIST;
- list_add(&dentry->d_lru, list);
+ d_shrink_add(dentry, list);
spin_unlock(&dentry->d_lock);
}
}
* another pass through the LRU.
*/
if (dentry->d_lockref.count) {
- list_del_init(&dentry->d_lru);
+ d_lru_isolate(dentry);
spin_unlock(&dentry->d_lock);
return LRU_REMOVED;
}
return LRU_ROTATE;
}
- dentry->d_flags |= DCACHE_SHRINK_LIST;
- list_move_tail(&dentry->d_lru, freeable);
- this_cpu_dec(nr_dentry_unused);
+ d_lru_shrink_move(dentry, freeable);
spin_unlock(&dentry->d_lock);
return LRU_REMOVED;
if (!spin_trylock(&dentry->d_lock))
return LRU_SKIP;
- dentry->d_flags |= DCACHE_SHRINK_LIST;
- list_move_tail(&dentry->d_lru, freeable);
- this_cpu_dec(nr_dentry_unused);
+ d_lru_shrink_move(dentry, freeable);
spin_unlock(&dentry->d_lock);
return LRU_REMOVED;
* list is non-empty and continue searching.
*/
-/**
- * have_submounts - check for mounts over a dentry
- * @parent: dentry to check.
- *
- * Return true if the parent or its subdirectories contain
- * a mount point
- */
-
static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
{
int *ret = data;
return D_WALK_CONTINUE;
}
+/**
+ * have_submounts - check for mounts over a dentry
+ * @parent: dentry to check.
+ *
+ * Return true if the parent or its subdirectories contain
+ * a mount point
+ */
int have_submounts(struct dentry *parent)
{
int ret = 0;
if (dentry->d_lockref.count) {
dentry_lru_del(dentry);
} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
- dentry_lru_del(dentry);
- list_add_tail(&dentry->d_lru, &data->dispose);
- dentry->d_flags |= DCACHE_SHRINK_LIST;
+ /*
+ * We can't use d_lru_shrink_move() because we
+ * need to get the global LRU lock and do the
+ * LRU accounting.
+ */
+ d_lru_del(dentry);
+ d_shrink_add(dentry, &data->dispose);
data->found++;
ret = D_WALK_NORETRY;
}
/**
* prepend_name - prepend a pathname in front of current buffer pointer
- * buffer: buffer pointer
- * buflen: allocated length of the buffer
- * name: name string and length qstr structure
+ * @buffer: buffer pointer
+ * @buflen: allocated length of the buffer
+ * @name: name string and length qstr structure
*
* With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
* make sure that either the old or the new name pointer and length are
* @buffer: pointer to the end of the buffer
* @buflen: pointer to buffer length
*
- * The function tries to write out the pathname without taking any lock other
- * than the RCU read lock to make sure that dentries won't go away. It only
- * checks the sequence number of the global rename_lock as any change in the
- * dentry's d_seq will be preceded by changes in the rename_lock sequence
- * number. If the sequence number had been change, it will restart the whole
- * pathname back-tracing sequence again. It performs a total of 3 trials of
- * lockless back-tracing sequences before falling back to take the
- * rename_lock.
+ * The function will first try to write out the pathname without taking any
+ * lock other than the RCU read lock to make sure that dentries won't go away.
+ * It only checks the sequence number of the global rename_lock as any change
+ * in the dentry's d_seq will be preceded by changes in the rename_lock
+ * sequence number. If the sequence number had been changed, it will restart
+ * the whole pathname back-tracing sequence again by taking the rename_lock.
+ * In this case, there is no need to take the RCU read lock as the recursive
+ * parent pointer references will keep the dentry chain alive as long as no
+ * rename operation is performed.
*/
static int prepend_path(const struct path *path,
const struct path *root,
return prepend(buffer, buflen, "(unreachable)", 13);
}
+static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
+{
+ unsigned seq;
+
+ do {
+ seq = read_seqcount_begin(&fs->seq);
+ *root = fs->root;
+ } while (read_seqcount_retry(&fs->seq, seq));
+}
+
/**
* d_path - return the path of a dentry
* @path: path to report
if (path->dentry->d_op && path->dentry->d_op->d_dname)
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
- get_fs_root(current->fs, &root);
+ rcu_read_lock();
+ get_fs_root_rcu(current->fs, &root);
br_read_lock(&vfsmount_lock);
error = path_with_deleted(path, &root, &res, &buflen);
br_read_unlock(&vfsmount_lock);
+ rcu_read_unlock();
+
if (error < 0)
res = ERR_PTR(error);
- path_put(&root);
return res;
}
EXPORT_SYMBOL(d_path);
return ERR_PTR(-ENAMETOOLONG);
}
+static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
+ struct path *pwd)
+{
+ unsigned seq;
+
+ do {
+ seq = read_seqcount_begin(&fs->seq);
+ *root = fs->root;
+ *pwd = fs->pwd;
+ } while (read_seqcount_retry(&fs->seq, seq));
+}
+
/*
* NOTE! The user-level library version returns a
* character pointer. The kernel system call just
{
int error;
struct path pwd, root;
- char *page = (char *) __get_free_page(GFP_USER);
+ char *page = __getname();
if (!page)
return -ENOMEM;
- get_fs_root_and_pwd(current->fs, &root, &pwd);
+ rcu_read_lock();
+ get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
error = -ENOENT;
br_read_lock(&vfsmount_lock);
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
- char *cwd = page + PAGE_SIZE;
- int buflen = PAGE_SIZE;
+ char *cwd = page + PATH_MAX;
+ int buflen = PATH_MAX;
prepend(&cwd, &buflen, "\0", 1);
error = prepend_path(&pwd, &root, &cwd, &buflen);
br_read_unlock(&vfsmount_lock);
+ rcu_read_unlock();
if (error < 0)
goto out;
}
error = -ERANGE;
- len = PAGE_SIZE + page - cwd;
+ len = PATH_MAX + page - cwd;
if (len <= size) {
error = len;
if (copy_to_user(buf, cwd, len))
}
} else {
br_read_unlock(&vfsmount_lock);
+ rcu_read_unlock();
}
out:
- path_put(&pwd);
- path_put(&root);
- free_page((unsigned long) page);
+ __putname(page);
return error;
}
projects / karo-tx-linux.git / blobdiff