stat-in-cached-readdir.patch

From 5f767dec5b3fc07f665fdd4fbd9eb728a790f35f Mon Sep 17 00:00:00 2001
From: Jan Palus <jpalus@fastmail.com>
Date: Mon, 17 Jun 2024 11:48:44 +0200
Subject: [PATCH] Fill stat info when returning cached data for readdir

Uncached and cached results for readdir were inconsistent -- the former
returned correct stat info for directory entries while the latter
didn't. That's because only names of entries were saved in cache without
stat info. In turn this leads to issues like
https://github.com/junegunn/fzf/issues/3832 since directory traversal
library (https://github.com/charlievieth/fastwalk in this case) relies
on proper stat info returned by readdir. Hence when unchached result was
returned it gave proper outcome, while with cached result it was wrong.

Cache stat info next to entry name to fix the issue. While file
attributes are saved in cache already, they use full path as key. To
avoid potentially plenty of allocations, string copying and cache
lookups to get each attr, let's keep a copy of stat struct independently
to be on the fast path.
---
 cache.c | 43 +++++++++++++++++++++++++++++++------------
 1 file changed, 31 insertions(+), 12 deletions(-)

diff --git a/cache.c b/cache.c
index 9436c5a7..c57829dc 100644
--- a/cache.c
+++ b/cache.c
@@ -14,6 +14,7 @@
 #include <errno.h>
 #include <glib.h>
 #include <pthread.h>
+#include <sys/stat.h>
 
 #define DEFAULT_CACHE_TIMEOUT_SECS 20
 #define DEFAULT_MAX_CACHE_SIZE 10000
@@ -40,7 +41,7 @@ static struct cache cache;
 struct node {
 	struct stat stat;
 	time_t stat_valid;
-	char **dir;
+	GPtrArray *dir;
 	time_t dir_valid;
 	char *link;
 	time_t link_valid;
@@ -63,14 +64,28 @@ struct file_handle {
 	unsigned long fs_fh;
 };
 
+struct cache_dirent {
+	char *name;
+	struct stat stat;
+};
+
 static void free_node(gpointer node_)
 {
 	struct node *node = (struct node *) node_;
-	g_strfreev(node->dir);
+	if (node->dir != NULL)
+		g_ptr_array_free(node->dir, TRUE);
 	g_free(node->link);
 	g_free(node);
 }
 
+static void free_cache_dirent(gpointer data) {
+	struct cache_dirent *cache_dirent = (struct cache_dirent *) data;
+	if (cache_dirent != NULL) {
+		g_free(cache_dirent->name);
+		g_free(cache_dirent);
+	}
+}
+
 static int cache_clean_entry(void *key_, struct node *node, time_t *now)
 {
 	(void) key_;
@@ -186,13 +201,14 @@ void cache_add_attr(const char *path, const struct stat *stbuf, uint64_t wrctr)
 	pthread_mutex_unlock(&cache.lock);
 }
 
-static void cache_add_dir(const char *path, char **dir)
+static void cache_add_dir(const char *path, GPtrArray *dir)
 {
 	struct node *node;
 
 	pthread_mutex_lock(&cache.lock);
 	node = cache_get(path);
-	g_strfreev(node->dir);
+	if (node->dir != NULL)
+		g_ptr_array_free(node->dir, TRUE);
 	node->dir = dir;
 	node->dir_valid = time(NULL) + cache.dir_timeout_secs;
 	if (node->dir_valid > node->valid)
@@ -341,7 +357,10 @@ static int cache_dirfill (void *buf, const char *name,
 	ch = (struct readdir_handle*) buf;
 	err = ch->filler(ch->buf, name, stbuf, off, flags);
 	if (!err) {
-		g_ptr_array_add(ch->dir, g_strdup(name));
+		struct cache_dirent *cdent = g_malloc(sizeof(struct cache_dirent));
+		cdent->name = g_strdup(name);
+		cdent->stat = *stbuf;
+		g_ptr_array_add(ch->dir, cdent);
 		if (stbuf->st_mode & S_IFMT) {
 			char *fullpath;
 			const char *basepath = !ch->path[1] ? "" : ch->path;
@@ -361,8 +380,9 @@ static int cache_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
 	struct readdir_handle ch;
 	struct file_handle *cfi;
 	int err;
-	char **dir;
+	GPtrArray *dir;
 	struct node *node;
+	struct cache_dirent **cdent;
 
 	assert(offset == 0);
 
@@ -371,9 +391,8 @@ static int cache_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
 	if (node != NULL && node->dir != NULL) {
 		time_t now = time(NULL);
 		if (node->dir_valid - now >= 0) {
-			for(dir = node->dir; *dir != NULL; dir++)
-				// FIXME: What about st_mode?
-				filler(buf, *dir, NULL, 0, 0);
+			for(cdent = (struct cache_dirent**)node->dir->pdata; *cdent != NULL; cdent++)
+				filler(buf, (*cdent)->name, &(*cdent)->stat, 0, 0);
 			pthread_mutex_unlock(&cache.lock);
 			return 0;
 		}
@@ -397,16 +416,16 @@ static int cache_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
 	ch.buf = buf;
 	ch.filler = filler;
 	ch.dir = g_ptr_array_new();
+	g_ptr_array_set_free_func(ch.dir, free_cache_dirent);
 	ch.wrctr = cache_get_write_ctr();
 	err = cache.next_oper->readdir(path, &ch, cache_dirfill, offset, fi, flags);
 	g_ptr_array_add(ch.dir, NULL);
-	dir = (char **) ch.dir->pdata;
+	dir = ch.dir;
 	if (!err) {
 		cache_add_dir(path, dir);
 	} else {
-		g_strfreev(dir);
+		g_ptr_array_free(dir, TRUE);
 	}
-	g_ptr_array_free(ch.dir, FALSE);
 
 	return err;
 }