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, 12 insertions, 4 deletions

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 81b15c623803..f06a4e525ece 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -282,11 +282,18 @@ static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
 	/*
 	 * Of the r and x bits, all (subject to umask) must be present. Of the
 	 * w bits, either all (subject to umask) or none must be present.
+	 *
+	 * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
 	 */
 	if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 		return -EPERM;
-	if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
-		return -EPERM;
+	if (fat_mode_can_hold_ro(inode)) {
+		if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
+			return -EPERM;
+	} else {
+		if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
+			return -EPERM;
+	}
 
 	*mode_ptr &= S_IFMT | perm;
 
@@ -316,8 +323,8 @@ int fat_setattr(struct dentry *dentry, struct iattr *attr)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 	struct inode *inode = dentry->d_inode;
-	int error = 0;
 	unsigned int ia_valid;
+	int error;
 
 	/*
 	 * Expand the file. Since inode_setattr() updates ->i_size
@@ -371,7 +378,8 @@ int fat_setattr(struct dentry *dentry, struct iattr *attr)
 			attr->ia_valid &= ~ATTR_MODE;
 	}
 
-	error = inode_setattr(inode, attr);
+	if (attr->ia_valid)
+		error = inode_setattr(inode, attr);
 out:
 	return error;
 }