bug#79508: [PATCH] tail: fix seeking backward

* src/tail.c (file_lines): Seek to the previous block instead of the
beginning (or a little before) of the block that was just scanned.
Otherwise, the same block is read and scanned (at least partially)
again. This bug was introduced by commit v9.7-219-g976f8abc1.
---
 src/tail.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tail.c b/src/tail.c
index b8bef1d91..c7779c77d 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -596,7 +596,7 @@ file_lines (char const *prettyname, int fd, struct stat const *sb,
           goto free_buffer;
         }
 
-      pos = xlseek (fd, -bufsize, SEEK_CUR, prettyname);
+      pos = xlseek (fd, -(bufsize + bytes_read), SEEK_CUR, prettyname);
       bytes_read = read (fd, buffer, bufsize);
       if (bytes_read < 0)
         {
-- 
2.51.0