[PATCH 2/2] implement uid mount option for ext3

[Ludwig Nussel]

Signed-off-by: Ludwig Nussel <ludwig.nussel@xxxxxxx>
---
 Documentation/filesystems/ext3.txt |    2 ++
 fs/ext3/inode.c                    |   11 ++++++++++-
 fs/ext3/super.c                    |    8 +++++++-
 include/linux/ext3_fs_sb.h         |    1 +
 4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt
index 570f9bd..abdb2f6 100644
--- a/Documentation/filesystems/ext3.txt
+++ b/Documentation/filesystems/ext3.txt
@@ -121,6 +121,8 @@ resgid=n		The group ID which may use the reserved blocks.
 
 resuid=n		The user ID which may use the reserved blocks.
 
+uid=n			Map root owned files to this uid.
+
 sb=n			Use alternate superblock at this location.
 
 quota
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 5f51fed..148a4d3 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -2766,6 +2766,9 @@ struct inode *ext3_iget(struct super_block *sb, unsigned long ino)
 		inode->i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
 		inode->i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
 	}
+	if (EXT3_SB(sb)->s_uid && inode->i_uid == 0) {
+		inode->i_uid = EXT3_SB(sb)->s_uid;
+	}
 	inode->i_nlink = le16_to_cpu(raw_inode->i_links_count);
 	inode->i_size = le32_to_cpu(raw_inode->i_size);
 	inode->i_atime.tv_sec = (signed)le32_to_cpu(raw_inode->i_atime);
@@ -2905,7 +2908,13 @@ static int ext3_do_update_inode(handle_t *handle,
 
 	ext3_get_inode_flags(ei);
 	raw_inode->i_mode = cpu_to_le16(inode->i_mode);
-	if(!(test_opt(inode->i_sb, NO_UID32))) {
+	if (EXT3_SB(inode->i_sb)->s_uid &&
+	    inode->i_uid == EXT3_SB(inode->i_sb)->s_uid) {
+		raw_inode->i_uid_high = 0;
+		raw_inode->i_uid_low  = 0;
+		raw_inode->i_gid_high = 0;
+		raw_inode->i_gid_low  = 0;
+	} else if(!(test_opt(inode->i_sb, NO_UID32))) {
 		raw_inode->i_uid_low = cpu_to_le16(low_16_bits(inode->i_uid));
 		raw_inode->i_gid_low = cpu_to_le16(low_16_bits(inode->i_gid));
 /*
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 524b349..b610242 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -779,7 +779,7 @@ enum {
 	Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
 	Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
 	Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,
-	Opt_grpquota
+	Opt_grpquota, Opt_uid
 };
 
 static const match_table_t tokens = {
@@ -832,6 +832,7 @@ static const match_table_t tokens = {
 	{Opt_usrquota, "usrquota"},
 	{Opt_barrier, "barrier=%u"},
 	{Opt_resize, "resize"},
+	{Opt_uid, "uid=%u"},
 	{Opt_err, NULL},
 };
 
@@ -1183,6 +1184,11 @@ set_qf_format:
 		case Opt_bh:
 			clear_opt(sbi->s_mount_opt, NOBH);
 			break;
+		case Opt_uid:
+			if (match_int(&args[0], &option))
+				return 0;
+			sbi->s_uid = option;
+			break;
 		default:
 			printk (KERN_ERR
 				"EXT3-fs: Unrecognized mount option \"%s\" "
diff --git a/include/linux/ext3_fs_sb.h b/include/linux/ext3_fs_sb.h
index f07f34d..751058a 100644
--- a/include/linux/ext3_fs_sb.h
+++ b/include/linux/ext3_fs_sb.h
@@ -47,6 +47,7 @@ struct ext3_sb_info {
 	ext3_fsblk_t s_sb_block;
 	uid_t s_resuid;
 	gid_t s_resgid;
+	uid_t s_uid;                    /* map root owned files to this uid */
 	unsigned short s_mount_state;
 	unsigned short s_pad;
 	int s_addr_per_block_bits;
-- 
1.6.2.1

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