fat: Fix ATTR_RO for directory

FAT has the ATTR_RO (read-only) attribute. But on Windows, the ATTR_RO
of the directory will be just ignored actually, and is used by only
applications as flag. E.g. it's setted for the customized folder by
Explorer.

http://msdn2.microsoft.com/en-us/library/aa969337.aspx

This adds "rodir" option. If user specified it, ATTR_RO is used as
read-only flag even if it's the directory. Otherwise, inode->i_mode
is not used to hold ATTR_RO (i.e. fat_mode_can_save_ro() returns 0).

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 313b645b8126..e9dce5d8e7a7 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -38,7 +38,8 @@ struct fat_mount_options {
                  flush:1,         /* write things quickly */
                  nocase:1,        /* Does this need case conversion? 0=need case conversion*/
                  usefree:1,       /* Use free_clusters for FAT32 */
-                 tz_utc:1;        /* Filesystem timestamps are in UTC */
+                 tz_utc:1,        /* Filesystem timestamps are in UTC */
+                 rodir:1;         /* allow ATTR_RO for directory */
 };
 
 #define FAT_HASH_BITS   8
@@ -120,15 +121,20 @@ static inline struct msdos_inode_info *MSDOS_I(struct inode *inode)
 /*
  * If ->i_mode can't hold S_IWUGO (i.e. ATTR_RO), we use ->i_attrs to
  * save ATTR_RO instead of ->i_mode.
+ *
+ * If it's directory and !sbi->options.rodir, ATTR_RO isn't read-only
+ * bit, it's just used as flag for app.
  */
 static inline int fat_mode_can_hold_ro(struct inode *inode)
 {
         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
         mode_t mask;
 
-        if (S_ISDIR(inode->i_mode))
+        if (S_ISDIR(inode->i_mode)) {
+                if (!sbi->options.rodir)
+                        return 0;
                 mask = ~sbi->options.fs_dmask;
-        else
+        } else
                 mask = ~sbi->options.fs_fmask;
 
         if (!(mask & S_IWUGO))
@@ -140,7 +146,7 @@ static inline int fat_mode_can_hold_ro(struct inode *inode)
 static inline mode_t fat_make_mode(struct msdos_sb_info *sbi,
                                    u8 attrs, mode_t mode)
 {
-        if (attrs & ATTR_RO)
+        if (attrs & ATTR_RO && !((attrs & ATTR_DIR) && !sbi->options.rodir))
                 mode &= ~S_IWUGO;
 
         if (attrs & ATTR_DIR)