[U-Boot] [PATCH 1/2] ext4: Allow reading files with non-zero offset, clamp read len

[Stephen Warren]

On 11/05/2016 06:32 PM, Stefan Brüns wrote:
> Support was already implemented, but not hooked up. This fixes several
> fails in the test cases.

> diff --git a/fs/ext4/ext4fs.c b/fs/ext4/ext4fs.c

> @@ -217,21 +217,16 @@ int ext4_read_file(const char *filename, void *buf, loff_t offset, loff_t len,

> -	if (len == 0)
> -		len = file_len;
> +	if ((len == 0) || (offset + len > file_len))
> +		len = (file_len - offset);

Isn't (offset + len > file_len) an error? It seems find to "read to EOF" 
if the caller specified len==0, but if they specified a specific len, 
then isn't it an error if len+offset exceeds the length of the file?

On the other hand, if this is how other filesystems work in U-Boot, it's 
fine. I suppose this is consistent with how POSIX read() works.

> diff --git a/include/ext4fs.h b/include/ext4fs.h

> -int ext4fs_read(char *buf, loff_t len, loff_t *actread);
> +int ext4fs_read(char *buf, loff_t offset, loff_t len, loff_t *actread);

Don't you need to update all callers of this function in this patch so 
the build doesn't break?