[PATCH 3.12 085/101] hfsplus: fix remount issue

[Jiri Slaby]

From: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>

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

===============

commit bd2c00353286d63542a8a0896a8c747f7c880edd upstream.

Current implementation of HFS+ driver has small issue with remount
option.  Namely, for example, you are unable to remount from RO mode
into RW mode by means of command "mount -o remount,rw /dev/loop0
/mnt/hfsplus".  Trying to execute sequence of commands results in an
error message:

  mount /dev/loop0 /mnt/hfsplus
  mount -o remount,ro /dev/loop0 /mnt/hfsplus
  mount -o remount,rw /dev/loop0 /mnt/hfsplus

  mount: you must specify the filesystem type

  mount -t hfsplus -o remount,rw /dev/loop0 /mnt/hfsplus

  mount: /mnt/hfsplus not mounted or bad option

The reason of such issue is failure of mount syscall:

  mount("/dev/loop0", "/mnt/hfsplus", 0x2282a60, MS_MGC_VAL|MS_REMOUNT, NULL) = -1 EINVAL (Invalid argument)

Namely, hfsplus_parse_options_remount() method receives empty "input"
argument and return false in such case.  As a result, hfsplus_remount()
returns -EINVAL error code.

This patch fixes the issue by means of return true for the case of empty
"input" argument in hfsplus_parse_options_remount() method.

Signed-off-by: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 fs/hfsplus/options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/hfsplus/options.c b/fs/hfsplus/options.c
index 968eab5bc1f5..68537e8b7a09 100644
--- a/fs/hfsplus/options.c
+++ b/fs/hfsplus/options.c
@@ -75,7 +75,7 @@ int hfsplus_parse_options_remount(char *input, int *force)
 	int token;
 
 	if (!input)
-		return 0;
+		return 1;
 
 	while ((p = strsep(&input, ",")) != NULL) {
 		if (!*p)
-- 
2.1.3

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