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

[Marek Szyprowski]

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");
-- 
2.17.1