[PATCH 6/7] ext4: determine group descriptor size for 64bit feature

[Antony Pavlov]

This is an adoption of the U-Boot commits

| commit fc214ef90910159f33fbe92a6cb77839a27fa8a6
| Author: Stefan Brüns <stefan.bruens at rwth-aachen.de>
| Date:   Sat Sep 17 02:10:07 2016 +0200
|
|     ext4: determine group descriptor size for 64bit feature
|
|     If EXT4_FEATURE_INCOMPAT_64BIT is set, the descriptor can be read from
|     the superblocks, otherwise it defaults to 32.
|
|     Signed-off-by: Stefan Brüns <stefan.bruens at rwth-aachen.de>

| commit 3cc5bbb8e68dc67b7c3d2fdebef69408e5271469
| Author: Stefan Brüns <stefan.bruens at rwth-aachen.de>
| Date:   Tue Dec 27 02:35:08 2016 +0100
|
|     fs/ext4: Initialize group descriptor size for revision level 0 filesystems
|
|     genext2fs creates revision level 0 filesystems, which are not readable
|     by u-boot due to the initialized group descriptor size field.
|     f798b1dda1c5de818b806189e523d1b75db7e72d
|
|     Reported-by: Kever Yang <kever.yang at rock-chips.com>
|     Reported-by: FrostyBytes at protonmail.com
|     Signed-off-by: Stefan Brüns <stefan.bruens at rwth-aachen.de>
|     Tested-by: Kever Yang <kever.yang at rock-chips.com>

Signed-off-by: Antony Pavlov <antonynpavlov at gmail.com>
---
 fs/ext4/ext4_common.c | 21 ++++++++++++++++-----
 fs/ext4/ext4fs.h      |  3 +++
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 9cbe3dbb1..f35eebc21 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -506,13 +506,24 @@ int ext4fs_mount(struct ext_filesystem *fs)
 		goto fail;
 	}
 
-	if (le32_to_cpu(data->sblock.revision_level) == 0)
+	if (le32_to_cpu(data->sblock.revision_level) == 0) {
 		fs->inodesz = 128;
-	else
-		fs->inodesz = le16_to_cpu(data->sblock.inode_size);
+		fs->gdsize = 32;
+	} else {
+		debug("EXT4 features COMPAT: %08x INCOMPAT: %08x RO_COMPAT: %08x\n",
+		      le32_to_cpu(data->sblock.feature_compatibility),
+		      le32_to_cpu(data->sblock.feature_incompat),
+		      le32_to_cpu(data->sblock.feature_ro_compat));
 
-	dev_info(fs->dev, "EXT2 rev %d, inode_size %d\n",
-	       le32_to_cpu(data->sblock.revision_level), fs->inodesz);
+		fs->inodesz = le16_to_cpu(data->sblock.inode_size);
+		fs->gdsize = le32_to_cpu(data->sblock.feature_incompat) &
+			EXT4_FEATURE_INCOMPAT_64BIT ?
+			le16_to_cpu(data->sblock.descriptor_size) : 32;
+	}
+
+	dev_info(fs->dev, "EXT2 rev %d, inode_size %d, descriptor size %d\n",
+	      le32_to_cpu(data->sblock.revision_level),
+	      fs->inodesz, fs->gdsize);
 
 	data->diropen.data = data;
 	data->diropen.ino = 2;
diff --git a/fs/ext4/ext4fs.h b/fs/ext4/ext4fs.h
index ead212d97..17a490a94 100644
--- a/fs/ext4/ext4fs.h
+++ b/fs/ext4/ext4fs.h
@@ -28,6 +28,7 @@
 #define EXT4_EXT_MAGIC			0xf30a
 #define EXT4_FEATURE_RO_COMPAT_GDT_CSUM	0x0010
 #define EXT4_FEATURE_INCOMPAT_EXTENTS	0x0040
+#define EXT4_FEATURE_INCOMPAT_64BIT	0x0080
 #define EXT4_INDIRECT_BLOCKS		12
 
 #define EXT4_BG_INODE_UNINIT		0x0001
@@ -81,6 +82,8 @@ struct ext_filesystem {
 	uint32_t inodesz;
 	/* Sectors per Block */
 	uint32_t sect_perblk;
+	/* Group Descriptor size */
+	uint16_t gdsize;
 	/* Group Descriptor Block Number */
 	uint32_t gdtable_blkno;
 	/* Total block groups of partition */
-- 
2.11.0