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

[Stefan Bruens]

On Samstag, 5. November 2016 21:22:43 CET Stephen Warren wrote:
> 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.

It matches behaviour of POSIX read() and u-boot's FAT implementation, and 
there is also the actread parameter the caller could/should check. 

> > 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?

Missed the calls from spl_ext.c, will send v2.

Kind regards,

Stefan

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