[U-Boot] [PATCH v3 1/6] fat: write: fix broken write to fragmented files

[Marek Szyprowski]

The code for handing file overwrite incorrectly assumed that the file on
disk is always contiguous. This resulted in corrupting disk structure
every time when write to existing fragmented file happened. Fix this
by adding proper check for cluster discontinuity and adjust chunk size
on each partial write.

Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov at toradex.com>
Reviewed-by: Lukasz Majewski <lukma at denx.de>
---
 fs/fat/fat_write.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
index 729cf39630..6cfa5b4565 100644
--- a/fs/fat/fat_write.c
+++ b/fs/fat/fat_write.c
@@ -794,6 +794,8 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
 
 			newclust = get_fatent(mydata, endclust);
 
+			if ((newclust - 1) != endclust)
+				break;
 			if (IS_LAST_CLUST(newclust, mydata->fatsize))
 				break;
 			if (CHECK_CLUST(newclust, mydata->fatsize)) {
@@ -811,7 +813,7 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
 			offset = 0;
 		else
 			offset = pos - cur_pos;
-		wsize = min(cur_pos + actsize, filesize) - pos;
+		wsize = min_t(unsigned long long, actsize, filesize - cur_pos);
 		if (get_set_cluster(mydata, curclust, offset,
 				    buffer, wsize, &actsize)) {
 			printf("Error get-and-setting cluster\n");
@@ -824,8 +826,6 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
 		if (filesize <= cur_pos)
 			break;
 
-		/* CHECK: newclust = get_fatent(mydata, endclust); */
-
 		if (IS_LAST_CLUST(newclust, mydata->fatsize))
 			/* no more clusters */
 			break;
-- 
2.17.1