Add ability to keep proc entry metadata

entries and their metadirectories may sometimes need to keep some extra
data around for file operations in them, so this lets them define
functions that can refcount this.

fs/proc.c

@@ -16,6 +16,9 @@ static int proc_lookup(const char *path, struct proc_entry *entry) {
         unsigned long index = 0;
         struct proc_entry next_entry;
         char entry_name[MAX_NAME];
+        if (entry->meta->ref) {
+            entry->meta->ref(entry);
+        }
         while (proc_dir_read(entry, &index, &next_entry)) {
             // tack on some dynamically generated attributes
             if (next_entry.meta->parent == NULL)
@@ -30,8 +33,14 @@ static int proc_lookup(const char *path, struct proc_entry *entry) {
             if (strcmp(entry_name, component) == 0)
                 goto found;
         }
+        if (entry->meta->unref) {
+            entry->meta->unref(entry);
+        }
         return _ENOENT;
 found:
+        if (entry->meta->unref) {
+            entry->meta->unref(entry);
+        }
         *entry = next_entry;
     }
     return err;
@@ -44,6 +53,9 @@ static struct fd *proc_open(struct mount *UNUSED(mount), const char *path, int U
     int err = proc_lookup(path, &entry);
     if (err < 0)
         return ERR_PTR(err);
+    if (entry.meta->ref) {
+        entry.meta->ref(&entry);
+    }
     struct fd *fd = fd_create(&procfs_fdops);
     fd->proc.entry = entry;
     fd->proc.data.data = NULL;
@@ -74,7 +86,14 @@ static int proc_stat(struct mount *UNUSED(mount), const char *path, struct statb
     int err = proc_lookup(path, &entry);
     if (err < 0)
         return err;
-    return proc_entry_stat(&entry, stat);
+    if (entry.meta->ref) {
+        entry.meta->ref(&entry);
+    }
+    int ret = proc_entry_stat(&entry, stat);
+    if (entry.meta->unref) {
+        entry.meta->unref(&entry);
+    }
+    return ret;
 }
 
 static int proc_fstat(struct fd *fd, struct statbuf *stat) {
@@ -165,6 +184,9 @@ static int proc_readdir(struct fd *fd, struct dir_entry *entry) {
 static int proc_close(struct fd *fd) {
     if (fd->proc.data.data != NULL)
         free(fd->proc.data.data);
+    if (fd->proc.entry.meta->unref) {
+        fd->proc.entry.meta->unref(&fd->proc.entry);
+    }
     return 0;
 }
 
@@ -184,7 +206,13 @@ static ssize_t proc_readlink(struct mount *UNUSED(mount), const char *path, char
         return _EINVAL;
 
     char target[MAX_PATH + 1];
+    if (entry.meta->ref) {
+        entry.meta->ref(&entry);
+    }
     err = entry.meta->readlink(&entry, target);
+    if (entry.meta->unref) {
+        entry.meta->unref(&entry);
+    }
     if (err < 0)
         return err;
     if (bufsize > strlen(target))

fs/proc.h

@@ -20,6 +20,10 @@ struct proc_dir_entry {
     const char *name;
     mode_t_ mode;
 
+    // files that need extra resource management
+    void (*ref)(struct proc_entry *entry);
+    void (*unref)(struct proc_entry *entry);
+
     // file with dynamic name
     void (*getname)(struct proc_entry *entry, char *buf);