[U-Boot] [PATCH v3 2/6] fat: write: fix broken write at non-zero file offset

[Tom Rini]

On Tue, Nov 26, 2019 at 09:15:08AM +0100, Marek Szyprowski wrote:

> Handling of the start file offset was broken in the current code. Although
> the code skipped the needed clusters, it then tried to continue write with
> current cluster set to EOF, what caused assertion. It also lacked adjusting
> filesize in case of writing at the end of file and adjusting in-cluster
> offset for partial overwrite.
> 
> This patch fixes all those issues.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
> ---
>  fs/fat/fat_write.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
> index 6cfa5b4565..7fb373589d 100644
> --- a/fs/fat/fat_write.c
> +++ b/fs/fat/fat_write.c
> @@ -756,14 +756,12 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
>  	/* go to cluster at pos */
>  	cur_pos = bytesperclust;
>  	while (1) {
> +		newclust = get_fatent(mydata, curclust);
>  		if (pos <= cur_pos)
>  			break;
> -		if (IS_LAST_CLUST(curclust, mydata->fatsize))
> +		if (IS_LAST_CLUST(newclust, mydata->fatsize))
>  			break;
> -
> -		newclust = get_fatent(mydata, curclust);
> -		if (!IS_LAST_CLUST(newclust, mydata->fatsize) &&
> -		    CHECK_CLUST(newclust, mydata->fatsize)) {
> +		if (CHECK_CLUST(newclust, mydata->fatsize)) {
>  			debug("curclust: 0x%x\n", curclust);
>  			debug("Invalid FAT entry\n");
>  			return -1;
> @@ -772,8 +770,8 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
>  		cur_pos += bytesperclust;
>  		curclust = newclust;
>  	}
> -	if (IS_LAST_CLUST(curclust, mydata->fatsize)) {
> -		assert(pos == cur_pos);
> +	if (pos == cur_pos && IS_LAST_CLUST(newclust, mydata->fatsize)) {
> +		filesize -= pos;
>  		goto set_clusters;
>  	}
>  
> @@ -814,6 +812,7 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
>  		else
>  			offset = pos - cur_pos;
>  		wsize = min_t(unsigned long long, actsize, filesize - cur_pos);
> +		wsize -= offset;
>  		if (get_set_cluster(mydata, curclust, offset,
>  				    buffer, wsize, &actsize)) {
>  			printf("Error get-and-setting cluster\n");

Adding in Heinrich and Akashi-san for more review on this, thanks!

-- 
Tom
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