ext4: optimize Hurd tests when reading/writing inodes

Set a in-memory superblock flag to indicate whether the file system is
designed to support the Hurd.

Also, add a sanity check to make sure the 64-bit feature is not set
for Hurd file systems, since i_file_acl_high conflicts with a
Hurd-specific field.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

3 files changed, 15 insertions, 6 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f4f889e6df83..e01135d791ca 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1001,6 +1001,8 @@ struct ext4_inode_info {
 #define EXT4_MOUNT2_STD_GROUP_SIZE      0x00000002 /* We have standard group
                                                       size of blocksize * 8
                                                       blocks */
+#define EXT4_MOUNT2_HURD_COMPAT         0x00000004 /* Support HURD-castrated
+                                                      file systems */
 
 #define clear_opt(sb, opt)              EXT4_SB(sb)->s_mount_opt &= \
                                                 ~EXT4_MOUNT_##opt
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ed2c13a7f293..b5e182acf9b9 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4168,8 +4168,7 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
         EXT4_INODE_GET_XTIME(i_atime, inode, raw_inode);
         EXT4_EINODE_GET_XTIME(i_crtime, ei, raw_inode);
 
-        if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
-            cpu_to_le32(EXT4_OS_HURD)) {
+        if (likely(!test_opt2(inode->i_sb, HURD_COMPAT))) {
                 inode->i_version = le32_to_cpu(raw_inode->i_disk_version);
                 if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
                         if (EXT4_FITS_IN_INODE(raw_inode, ei, i_version_hi))
@@ -4345,8 +4344,7 @@ static int ext4_do_update_inode(handle_t *handle,
                 goto out_brelse;
         raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
         raw_inode->i_flags = cpu_to_le32(ei->i_flags & 0xFFFFFFFF);
-        if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
-            cpu_to_le32(EXT4_OS_HURD))
+        if (likely(!test_opt2(inode->i_sb, HURD_COMPAT)))
                 raw_inode->i_file_acl_high =
                         cpu_to_le16(ei->i_file_acl >> 32);
         raw_inode->i_file_acl_lo = cpu_to_le32(ei->i_file_acl);
@@ -4391,8 +4389,7 @@ static int ext4_do_update_inode(handle_t *handle,
                         raw_inode->i_block[block] = ei->i_data[block];
         }
 
-        if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
-            cpu_to_le32(EXT4_OS_HURD)) {
+        if (likely(!test_opt2(inode->i_sb, HURD_COMPAT))) {
                 raw_inode->i_disk_version = cpu_to_le32(inode->i_version);
                 if (ei->i_extra_isize) {
                         if (EXT4_FITS_IN_INODE(raw_inode, ei, i_version_hi))
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 5a51af7d0335..f3c667091618 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3580,6 +3580,16 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                        "feature flags set on rev 0 fs, "
                        "running e2fsck is recommended");
 
+        if (es->s_creator_os == cpu_to_le32(EXT4_OS_HURD)) {
+                set_opt2(sb, HURD_COMPAT);
+                if (EXT4_HAS_INCOMPAT_FEATURE(sb,
+                                              EXT4_FEATURE_INCOMPAT_64BIT)) {
+                        ext4_msg(sb, KERN_ERR,
+                                 "The Hurd can't support 64-bit file systems");
+                        goto failed_mount;
+                }
+        }
+
         if (IS_EXT2_SB(sb)) {
                 if (ext2_feature_set_ok(sb))
                         ext4_msg(sb, KERN_INFO, "mounting ext2 file system "