[PATCH 5/5] logger: clarify non-update of w_off in do_write_log_from_user

[Tim Bird <tim.bird@am.sony.com>]

Add comment to explain when w_off is not updated in case of failed second
fragment copy to buffer.

Signed-off-by: Tim Bird <tim.bird@am.sony.com>
---
 drivers/staging/android/logger.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c
index 8d9d4f1..115d8ed 100644
--- a/drivers/staging/android/logger.c
+++ b/drivers/staging/android/logger.c
@@ -330,6 +330,12 @@ static ssize_t do_write_log_from_user(struct logger_log *log,

 	if (count != len)
 		if (copy_from_user(log->buffer, buf + len, count - len))
+			/*
+			 * Note that by not updating w_off, this abandons the
+			 * portion of the new entry that *was* successfully
+			 * copied, just above.  This is intentional to avoid
+			 * message corruption from missing fragments.
+			 */
 			return -EFAULT;

 	log->w_off = logger_offset(log, log->w_off + count);
-- 
1.7.2.3