3.13.11.10 -stable review patch.  If anyone has any objections, please let me 
know.

------------------

From: Artem Bityutskiy <[email protected]>

commit ba29e721eb2df6df8f33c1f248388bb037a47914 upstream.

Hu (hujianyang <[email protected]>) discovered an issue in the
'empty_log_bytes()' function, which calculates how many bytes are left in the
log:

"
If 'c->lhead_lnum + 1 == c->ltail_lnum' and 'c->lhead_offs == c->leb_size', 'h'
would equalent to 't' and 'empty_log_bytes()' would return 'c->log_bytes'
instead of 0.
"

At this point it is not clear what would be the consequences of this, and
whether this may lead to any problems, but this patch addresses the issue just
in case.

Tested-by: hujianyang <[email protected]>
Reported-by: hujianyang <[email protected]>
Signed-off-by: Artem Bityutskiy <[email protected]>
Signed-off-by: Kamal Mostafa <[email protected]>
---
 fs/ubifs/log.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ubifs/log.c b/fs/ubifs/log.c
index 36bd4ef..bcae6d4 100644
--- a/fs/ubifs/log.c
+++ b/fs/ubifs/log.c
@@ -106,10 +106,14 @@ static inline long long empty_log_bytes(const struct 
ubifs_info *c)
        h = (long long)c->lhead_lnum * c->leb_size + c->lhead_offs;
        t = (long long)c->ltail_lnum * c->leb_size;
 
-       if (h >= t)
+       if (h > t)
                return c->log_bytes - h + t;
-       else
+       else if (h != t)
                return t - h;
+       else if (c->lhead_lnum != c->ltail_lnum)
+               return 0;
+       else
+               return c->log_bytes;
 }
 
 /**
-- 
1.9.1

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