[PATCH 16/21] fat: Fix ATTR_RO for directory

OGAWA Hirofumi
2008-10-15T14:07:31Z

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>
---

Documentation/filesystems/vfat.txt | 8 ++++++++
fs/fat/fat.h | 14 ++++++++++----
fs/fat/file.c | 16 ++++++++++++----
fs/fat/inode.c | 17 +++++++++++++----
4 files changed, 43 insertions(+), 12 deletions(-)

diff -puN fs/fat/inode.c~fat-attrs-add-rodir fs/fat/inode.c
--- linux-2.6/fs/fat/inode.c~fat-attrs-add-rodir 2008-10-15 20:33:17.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/inode.c 2008-10-15 20:33:17.000000000 +0900
@@ -813,8 +813,10 @@ static int fat_show_options(struct seq_f
seq_puts(m, ",uni_xlate");
if (!opts->numtail)
seq_puts(m, ",nonumtail");
+ if (opts->rodir)
+ seq_puts(m, ",rodir");
}
- if (sbi->options.flush)
+ if (opts->flush)
seq_puts(m, ",flush");
if (opts->tz_utc)
seq_puts(m, ",tz=UTC");
@@ -830,7 +832,7 @@ enum {
Opt_charset, Opt_shortname_lower, Opt_shortname_win95,
Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
- Opt_obsolate, Opt_flush, Opt_tz_utc, Opt_err,
+ Opt_obsolate, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err,
};

static const match_table_t fat_tokens = {
@@ -902,6 +904,7 @@ static const match_table_t vfat_tokens =
{Opt_nonumtail_yes, "nonumtail=yes"},
{Opt_nonumtail_yes, "nonumtail=true"},
{Opt_nonumtail_yes, "nonumtail"},
+ {Opt_rodir, "rodir"},
{Opt_err, NULL}
};

@@ -921,10 +924,13 @@ static int parse_options(char *options,
opts->allow_utime = -1;
opts->codepage = fat_default_codepage;
opts->iocharset = fat_default_iocharset;
- if (is_vfat)
+ if (is_vfat) {
opts->shortname = VFAT_SFN_DISPLAY_LOWER|VFAT_SFN_CREATE_WIN95;
- else
+ opts->rodir = 0;
+ } else {
opts->shortname = 0;
+ opts->rodir = 1;
+ }
opts->name_check = 'n';
opts->quiet = opts->showexec = opts->sys_immutable = opts->dotsOK = 0;
opts->utf8 = opts->unicode_xlate = 0;
@@ -1075,6 +1081,9 @@ static int parse_options(char *options,
case Opt_nonumtail_yes: /* empty or 1 or yes or true */
opts->numtail = 0; /* negated option */
break;
+ case Opt_rodir:
+ opts->rodir = 1;
+ break;

/* obsolete mount options */
case Opt_obsolate:
diff -puN fs/fat/fat.h~fat-attrs-add-rodir fs/fat/fat.h
--- linux-2.6/fs/fat/fat.h~fat-attrs-add-rodir 2008-10-15 20:33:17.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/fat.h 2008-10-15 20:33:17.000000000 +0900
@@ -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 *M
/*
* 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(s
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)
diff -puN fs/fat/file.c~fat-attrs-add-rodir fs/fat/file.c
--- linux-2.6/fs/fat/file.c~fat-attrs-add-rodir 2008-10-15 20:33:17.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/file.c 2008-10-15 20:33:17.000000000 +0900
@@ -282,11 +282,18 @@ static int fat_sanitize_mode(const struc
/*
* 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, s
{
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, s
attr->ia_valid &= ~ATTR_MODE;
}

- error = inode_setattr(inode, attr);
+ if (attr->ia_valid)
+ error = inode_setattr(inode, attr);
out:
return error;
}
diff -puN Documentation/filesystems/vfat.txt~fat-attrs-add-rodir Documentation/filesystems/vfat.txt
--- linux-2.6/Documentation/filesystems/vfat.txt~fat-attrs-add-rodir 2008-10-15 20:33:17.000000000 +0900
+++ linux-2.6-hirofumi/Documentation/filesystems/vfat.txt 2008-10-15 20:33:17.000000000 +0900
@@ -124,6 +124,14 @@ sys_immutable -- If set, ATTR_SYS attrib
flush -- If set, the filesystem will try to flush to disk more
early than normal. Not set by default.

+rodir -- 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.
+
+ If you want to use ATTR_RO as read-only flag even for
+ the directory, set this option.
+
<bool>: 0,1,yes,no,true,false

TODO
_