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authorTavian Barnes <tavianator@tavianator.com>2023-03-23 13:59:48 -0400
committerTavian Barnes <tavianator@tavianator.com>2023-06-13 11:06:47 -0400
commit6719107e95a41b9ef241bdaa272eed505865710c (patch)
tree0d44c4640ef123ee8f74e051b6fe5c628d62de95
parent9dca9f2bcd06f921312762e0b07254f5f8f51fc2 (diff)
downloadbfs-6719107e95a41b9ef241bdaa272eed505865710c.tar.xz
dir: New bfs_polldir() function for directory readahead
-rw-r--r--src/dir.c88
-rw-r--r--src/dir.h10
-rw-r--r--src/ioq.c4
3 files changed, 80 insertions, 22 deletions
diff --git a/src/dir.c b/src/dir.c
index 126f473..b9fd74d 100644
--- a/src/dir.c
+++ b/src/dir.c
@@ -107,7 +107,10 @@ struct bfs_dir {
// sys_dirent buf[];
#else
DIR *dir;
+ struct dirent *de;
#endif
+
+ bool eof;
};
#if BFS_GETDENTS
@@ -152,8 +155,10 @@ struct bfs_dir *bfs_opendir(int at_fd, const char *at_path) {
free(dir);
return NULL;
}
+ dir->de = NULL;
#endif
+ dir->eof = false;
return dir;
}
@@ -165,38 +170,52 @@ int bfs_dirfd(const struct bfs_dir *dir) {
#endif
}
-/** Convert de->d_type to a bfs_type, if it exists. */
-static enum bfs_type bfs_d_type(const sys_dirent *de) {
-#ifdef DTTOIF
- return bfs_mode_to_type(DTTOIF(de->d_type));
-#else
- return BFS_UNKNOWN;
-#endif
-}
-
-/** Read a single directory entry. */
-static int bfs_getdent(struct bfs_dir *dir, const sys_dirent **de) {
+int bfs_polldir(struct bfs_dir *dir) {
#if BFS_GETDENTS
+ if (dir->pos < dir->size) {
+ return 1;
+ } else if (dir->eof) {
+ return 0;
+ }
+
char *buf = (char *)(dir + 1);
+ ssize_t size = bfs_getdents(dir->fd, buf, BUF_SIZE);
+ if (size == 0) {
+ dir->eof = true;
+ return 0;
+ } else if (size < 0) {
+ return -1;
+ }
- if (dir->pos >= dir->size) {
- ssize_t ret = bfs_getdents(dir->fd, buf, BUF_SIZE);
- if (ret <= 0) {
- return ret;
+ dir->pos = 0;
+ dir->size = size;
+
+ // Like read(), getdents() doesn't indicate EOF until another call returns zero.
+ // Check that eagerly here to hopefully avoid a syscall in the last bfs_readdir().
+ size_t rest = BUF_SIZE - size;
+ if (rest >= sizeof(sys_dirent)) {
+ size = bfs_getdents(dir->fd, buf + size, rest);
+ if (size > 0) {
+ dir->size += size;
+ } else if (size == 0) {
+ dir->eof = true;
}
- dir->pos = 0;
- dir->size = ret;
}
- *de = (void *)(buf + dir->pos);
- dir->pos += (*de)->d_reclen;
return 1;
-#else
+#else // !BFS_GETDENTS
+ if (dir->de) {
+ return 1;
+ } else if (dir->eof) {
+ return 0;
+ }
+
errno = 0;
- *de = readdir(dir->dir);
- if (*de) {
+ dir->de = readdir(dir->dir);
+ if (dir->de) {
return 1;
} else if (errno == 0) {
+ dir->eof = true;
return 0;
} else {
return -1;
@@ -204,6 +223,22 @@ static int bfs_getdent(struct bfs_dir *dir, const sys_dirent **de) {
#endif
}
+/** Read a single directory entry. */
+static int bfs_getdent(struct bfs_dir *dir, const sys_dirent **de) {
+ int ret = bfs_polldir(dir);
+ if (ret > 0) {
+#if BFS_GETDENTS
+ char *buf = (char *)(dir + 1);
+ *de = (const sys_dirent *)(buf + dir->pos);
+ dir->pos += (*de)->d_reclen;
+#else
+ *de = dir->de;
+ dir->de = NULL;
+#endif
+ }
+ return ret;
+}
+
/** Skip ".", "..", and deleted/empty dirents. */
static bool skip_dirent(const sys_dirent *de) {
#if __FreeBSD__
@@ -217,6 +252,15 @@ static bool skip_dirent(const sys_dirent *de) {
return name[0] == '.' && (name[1] == '\0' || (name[1] == '.' && name[2] == '\0'));
}
+/** Convert de->d_type to a bfs_type, if it exists. */
+static enum bfs_type bfs_d_type(const sys_dirent *de) {
+#ifdef DTTOIF
+ return bfs_mode_to_type(DTTOIF(de->d_type));
+#else
+ return BFS_UNKNOWN;
+#endif
+}
+
int bfs_readdir(struct bfs_dir *dir, struct bfs_dirent *de) {
while (true) {
const sys_dirent *sysde;
diff --git a/src/dir.h b/src/dir.h
index e0fe913..6fe7ae2 100644
--- a/src/dir.h
+++ b/src/dir.h
@@ -80,6 +80,16 @@ struct bfs_dir *bfs_opendir(int at_fd, const char *at_path);
int bfs_dirfd(const struct bfs_dir *dir);
/**
+ * Performs any I/O necessary for the next bfs_readdir() call.
+ *
+ * @param dir
+ * The directory to poll.
+ * @return
+ * 1 on success, 0 on EOF, or -1 on failure.
+ */
+int bfs_polldir(struct bfs_dir *dir);
+
+/**
* Read a directory entry.
*
* @param dir
diff --git a/src/ioq.c b/src/ioq.c
index 1b61fb0..74d2e09 100644
--- a/src/ioq.c
+++ b/src/ioq.c
@@ -158,6 +158,10 @@ static void *ioq_work(void *ptr) {
res->ptr = req.ptr;
res->dir = bfs_opendir(req.dfd, req.path);
res->error = errno;
+ if (res->dir) {
+ bfs_polldir(res->dir);
+ }
+
ioqq_push(ioq->ready, cmd);
}