[PATCH v2 4/4] fs: fat: Support basic file rename

[Daniel Venzin]

This implementation currently does not support
moving files between directories.

Signed-off-by: Daniel Venzin <Daniel.Venzin at mt.com>

---

Changes in v2:
- Separate the rename implementation from changes in the filesystem layer
- Eliminate code duplication with delete_dentry_long(..)
- Ensure that the source file exists, but not the destination file
- Free the fatbuf if it has been reinitialized with fat_itr_root
- Delete orphaned FAT entry after copying file metadata

 fs/fat/fat_write.c | 110 +++++++++++++++++++++++++++++++++++++++++++++
 fs/fs.c            |   2 +-
 include/fat.h      |   1 +
 3 files changed, 112 insertions(+), 1 deletion(-)

diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
index c78b80e0b7a..2273bf16053 100644
--- a/fs/fat/fat_write.c
+++ b/fs/fat/fat_write.c
@@ -1821,3 +1821,113 @@ exit:
 	free(dotdent);
 	return ret;
 }
+
+int file_fat_rename(const char *path, const char *new_filename)
+{
+	fsdata datablock = { .fatbuf = NULL, };
+	fat_itr *itr = NULL;
+
+	dir_entry *dentry;
+
+	char new_path[VFAT_MAXLEN_BYTES];
+	char *path_copy, *dirname, *basename;
+
+	loff_t actwrite;
+
+	__u16 starthi, start;
+	__u32 size, entry;
+
+	int ret = -1;
+
+	path_copy = strdup(path);
+	if (!path_copy)
+		goto exit;
+
+	split_filename(path_copy, &dirname, &basename);
+	snprintf(new_path, sizeof(new_path), "%s/%s", dirname, new_filename);
+
+	if (!fat_exists(path)) {
+		ret = -ENOENT;
+		goto exit;
+	}
+
+	if (fat_exists(new_path)) {
+		ret = -EEXIST;
+		goto exit;
+	}
+
+	ret = file_fat_write(new_path, &actwrite, 0, 0, &actwrite);
+	if (ret)
+		goto exit;
+
+	itr = malloc_cache_aligned(sizeof(*itr));
+	if (!itr) {
+		ret = -ENOMEM;
+		goto exit;
+	}
+
+	ret = fat_itr_root(itr, &datablock);
+	if (ret)
+		goto exit;
+
+	ret = fat_itr_resolve(itr, path, TYPE_FILE);
+	if (ret)
+		goto exit;
+
+	dentry = itr->dent;
+
+	starthi = dentry->starthi;
+	start = dentry->start;
+	size = dentry->size;
+
+	free(datablock.fatbuf);
+	datablock.fatbuf = NULL;
+
+	ret = fat_itr_root(itr, &datablock);
+	if (ret)
+		goto exit;
+
+	ret = fat_itr_resolve(itr, new_path, TYPE_FILE);
+	if (ret)
+		goto exit;
+
+	dentry = itr->dent;
+
+	fsdata *mydata = itr->fsdata;
+
+	entry = START(dentry);
+
+	dentry->starthi = starthi;
+	dentry->start = start;
+	dentry->size = size;
+
+	ret = flush_dir(itr);
+	if (ret)
+		goto exit;
+
+	clear_fatent(mydata, entry);
+	if (flush_dirty_fat_buffer(mydata) < 0) {
+		printf("Error: flush fat buffer\n");
+		ret = -EIO;
+		goto exit;
+	}
+
+	free(datablock.fatbuf);
+	datablock.fatbuf = NULL;
+
+	ret = fat_itr_root(itr, &datablock);
+	if (ret)
+		goto exit;
+
+	ret = fat_itr_resolve(itr, path, TYPE_FILE);
+	if (ret)
+		goto exit;
+
+	ret = delete_dentry_long(itr, FATENT_CLEAR_SKIP);
+
+exit:
+	free(path_copy);
+	free(datablock.fatbuf);
+	free(itr);
+	return ret;
+}
diff --git a/fs/fs.c b/fs/fs.c
index b746d05ebcd..3576d5c6644 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -208,7 +208,7 @@ static struct fstype_info fstypes[] = {
 		.write = file_fat_write,
 		.unlink = fat_unlink,
 		.mkdir = fat_mkdir,
-		.rename = fs_rename_unsupported,
+		.rename = file_fat_rename,
 #else
 		.write = fs_write_unsupported,
 		.unlink = fs_unlink_unsupported,
diff --git a/include/fat.h b/include/fat.h
index 3dce99a23cf..415ebd7b7c8 100644
--- a/include/fat.h
+++ b/include/fat.h
@@ -207,6 +207,7 @@ int fat_readdir(struct fs_dir_stream *dirs, struct fs_dirent **dentp);
 void fat_closedir(struct fs_dir_stream *dirs);
 int fat_unlink(const char *filename);
 int fat_mkdir(const char *dirname);
+int file_fat_rename(const char *path, const char *new_filename);
 void fat_close(void);
 void *fat_next_cluster(fat_itr *itr, unsigned int *nbytes);
 
-- 
2.47.2