Message-Id: <1362508235-4656-1-git-send-email-arvidjaar@gmail.com>
Date:	Tue,  5 Mar 2013 22:30:35 +0400
From:	Andrey Borzenkov <arvidjaar@...il.com>
To:	grub-devel@....org
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH] add ext4 inode inline data support to grub2

Add support for reading inode inline data as supported by ext4
as of linux kernel 3.8.

grub_ext2_inode_read() - read full inode (not only minimal compatible
ext2 part) and use it to search for inline data. Additionally it
saves inode block and offset for later use in grub_ext2_file_read for
inline data.

grub_ext2_find_inline_data() - search for extended attribute "data" in
system namespace. if present, inode has inline data. Calculate offset
and store it and size. Non-zero offset is used as flag that inline data
is present.

grub_ext2_file_read() - if inode has inline data, it is stored in up
to two chunks - in place of block pointers and in available space after
inode proper. It uses standard grub_disk_read() so all hooks are called
if present.

To actually create inline data EXT4_FEATURE_INCOMPAT_INLINE_DATA must
be present in superblock. As of today e2fsprogs refuse to touch filesystem
if this flag is present; the only way to set it is to use debugfs
directly.

Patch was lightly tested using grub-fstest on a ext4 image created under
3.8 with EXT4_FEATURE_INCOMPAT_INLINE_DATA set using debugfs. Tested were
inline files, inline directories and inline symlinks.

Signed-off-by: Andrey Borzenkov <arvidjaar@...il.com>

---
 grub-core/fs/ext2.c |  255 ++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 214 insertions(+), 41 deletions(-)

diff --git a/grub-core/fs/ext2.c b/grub-core/fs/ext2.c
index 18429ac..7304891 100644
--- a/grub-core/fs/ext2.c
+++ b/grub-core/fs/ext2.c
@@ -89,6 +89,9 @@ GRUB_MOD_LICENSE ("GPLv3+");
 #define EXT4_FEATURE_RO_COMPAT_GDT_CSUM		0x0010
 #define EXT4_FEATURE_RO_COMPAT_DIR_NLINK	0x0020
 #define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE	0x0040
+#define EXT4_FEATURE_RO_COMPAT_QUOTA            0x0100
+#define EXT4_FEATURE_RO_COMPAT_BIGALLOC         0x0200
+#define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM    0x0400
 /* Superblock filesystem feature flags (back-incompatible)
  * A filesystem with any of these enabled should not be attempted to be read
  * by a driver that does not understand them, since they usually indicate
@@ -101,13 +104,19 @@ GRUB_MOD_LICENSE ("GPLv3+");
 #define EXT4_FEATURE_INCOMPAT_EXTENTS		0x0040 /* Extents used */
 #define EXT4_FEATURE_INCOMPAT_64BIT		0x0080
 #define EXT4_FEATURE_INCOMPAT_FLEX_BG		0x0200
+#define EXT4_FEATURE_INCOMPAT_EA_INODE          0x0400 /* EA in inode */
+#define EXT4_FEATURE_INCOMPAT_DIRDATA           0x1000 /* data in dirent */
+#define EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM  0x2000 /* use crc32c for bg */
+#define EXT4_FEATURE_INCOMPAT_LARGEDIR          0x4000 /* >2GB or 3-lvl htree */
+#define EXT4_FEATURE_INCOMPAT_INLINE_DATA       0x8000 /* data in inode */
 
 /* The set of back-incompatible features this driver DOES support. Add (OR)
  * flags here as the related features are implemented into the driver.  */
 #define EXT2_DRIVER_SUPPORTED_INCOMPAT ( EXT2_FEATURE_INCOMPAT_FILETYPE \
                                        | EXT4_FEATURE_INCOMPAT_EXTENTS  \
                                        | EXT4_FEATURE_INCOMPAT_FLEX_BG \
-                                       | EXT4_FEATURE_INCOMPAT_64BIT)
+                                       | EXT4_FEATURE_INCOMPAT_64BIT \
+				       | EXT4_FEATURE_INCOMPAT_INLINE_DATA)
 /* List of rationales for the ignored "incompatible" features:
  * needs_recovery: Not really back-incompatible - was added as such to forbid
  *                 ext2 drivers from mounting an ext3 volume with a dirty
@@ -308,12 +317,40 @@ struct grub_ext4_extent_idx
   grub_uint16_t unused;
 };
 
+#define EXT4_XATTR_MAGIC	0xEA020000
+#define EXT4_XATTR_INDEX_SYSTEM	7
+#define EXT4_XATTR_SYSTEM_DATA	"data"
+#define EXT4_INLINE_DOTDOT_SIZE	4
+
+struct grub_ext4_xattr_entry
+{
+  grub_uint8_t name_len;	/* length of name */
+  grub_uint8_t name_index;	/* attribute name index */
+  grub_uint16_t value_offs;	/* offset in disk block of value */
+  grub_uint32_t value_block;	/* disk block attribute is stored on */
+  grub_uint32_t value_size;	/* size of attribute value */
+  grub_uint32_t hash;		/* hash value of name and value */
+  char name[0];			/* attribute name */
+};
+
+#define EXT4_XATTR_LEN(name_len) \
+  (((name_len) + sizeof(struct grub_ext4_xattr_entry) + 3) & ~3)
+#define EXT4_XATTR_NEXT(entry) \
+  ((struct grub_ext4_xattr_entry *)( \
+   (char *)(entry) + EXT4_XATTR_LEN((entry)->name_len)))
+#define IS_LAST_ENTRY(entry) (*(grub_uint32_t *)(entry) == 0)
+
+
 struct grub_fshelp_node
 {
   struct grub_ext2_data *data;
   struct grub_ext2_inode inode;
   int ino;
   int inode_read;
+  grub_disk_addr_t inode_base;	/* Inode filesystem block */
+  grub_off_t inode_offs;	/* Inode offset in filesystem block */
+  grub_off_t inline_offs;	/* Offset of inline data from start of inode */
+  grub_size_t inline_size;	/* Size of inline data */
 };
 
 /* Information about a "mounted" ext2 filesystem.  */
@@ -330,6 +367,61 @@ static grub_dl_t my_mod;
 
 .
 
+/* Inline data is stored using inline extended attributes. Attributes consist
+   of entry and value. Entries start after inode proper, following 4 bytes
+   magic header. Each entry is 4 bytes aligned, end of list is marked with
+   4 bytes zero. Values are stored after entries.
+   
+   Inline data is stored as system attribute with name "data". First part of
+   data is kept in space reserved for block pointers, so it is valid for value
+   size to be zero. Offset is apparently non-zero even in this case.
+ */
+inline static void
+grub_ext2_find_inline_data (struct grub_fshelp_node *node, grub_size_t isize, grub_uint8_t *inode)
+{
+  grub_size_t extra;
+  grub_uint32_t *ihdr;
+  struct grub_ext4_xattr_entry *entry;
+  grub_uint8_t *iend = inode + isize - sizeof (grub_uint32_t);
+
+  node->inline_offs = 0;
+
+  if (isize < EXT2_GOOD_OLD_INODE_SIZE + sizeof (grub_uint16_t))
+    return;
+  extra = grub_le_to_cpu16 (*(grub_uint16_t *)(inode + EXT2_GOOD_OLD_INODE_SIZE));
+  if (EXT2_GOOD_OLD_INODE_SIZE + extra + sizeof (*ihdr) > isize)
+    return;
+  ihdr = (grub_uint32_t *)(inode + EXT2_GOOD_OLD_INODE_SIZE + extra);
+  if (*ihdr != grub_cpu_to_le32_compile_time (EXT4_XATTR_MAGIC))
+    return;
+  entry = (struct grub_ext4_xattr_entry *)(ihdr + 1);
+  for (; (grub_uint8_t *)entry < iend && !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry))
+    {
+      grub_size_t value_size;
+      grub_off_t value_offs;
+
+      if (entry->value_block)
+	continue;
+      if (entry->name_index != EXT4_XATTR_INDEX_SYSTEM)
+	continue;
+      if (entry->name_len != sizeof (EXT4_XATTR_SYSTEM_DATA) - 1)
+	continue;
+      if (grub_memcmp (entry->name, EXT4_XATTR_SYSTEM_DATA, sizeof (EXT4_XATTR_SYSTEM_DATA) - 1))
+	continue;
+      value_size = grub_le_to_cpu32 (entry->value_size);
+      value_offs = grub_le_to_cpu16 (entry->value_offs);
+      /* extra is additional size of base inode. Extended attributes start
+	 after base inode, offset is calculated from the end of extended
+	 attributes header.
+      */
+      if (EXT2_GOOD_OLD_INODE_SIZE + extra + sizeof (*ihdr) + value_offs + value_size > isize)
+	continue;
+      node->inline_offs = EXT2_GOOD_OLD_INODE_SIZE + extra + sizeof (*ihdr) + value_offs;
+      node->inline_size = value_size;
+      return;
+    }
+}
+
 /* Read into BLKGRP the blockgroup descriptor of blockgroup GROUP of
    the mounted filesystem DATA.  */
 inline static grub_err_t
@@ -528,6 +620,52 @@ grub_ext2_read_file (grub_fshelp_node_t node,
 		     grub_disk_read_hook_t read_hook, void *read_hook_data,
 		     grub_off_t pos, grub_size_t len, char *buf)
 {
+  /* Does inode have inine data? */
+  if (node->inline_offs)
+    {
+      grub_size_t cp_len;
+      grub_off_t cp_pos;
+      grub_ssize_t total = 0;
+
+      if (pos < 60)
+	{
+	  cp_pos = node->inode_offs + ((char *)&node->inode.blocks - (char *)&node->inode) + pos;
+	  cp_len = 60 - pos;
+	  if (cp_len > len)
+	    cp_len = len;
+
+	  node->data->disk->read_hook = read_hook;
+	  node->data->disk->read_hook_data = read_hook_data;
+	  grub_disk_read (node->data->disk, node->inode_base, cp_pos,
+			  cp_len, buf);
+	  node->data->disk->read_hook = 0;
+	  if (grub_errno)
+	    return -1;
+	  pos += cp_len;
+	  buf += cp_len;
+	  len -= cp_len;
+	  total = cp_len;
+	}
+
+      if (len)
+	{
+	  pos -= 60;
+	  if (pos >= node->inline_size)
+	    return 0;
+	  if (pos + len > node->inline_size)
+	    len = node->inline_size - pos;
+	  cp_pos = node->inode_offs + node->inline_offs + pos;
+	  node->data->disk->read_hook = read_hook;
+	  node->data->disk->read_hook_data = read_hook_data;
+	  grub_disk_read (node->data->disk, node->inode_base, cp_pos,
+			  len, buf);
+	  node->data->disk->read_hook = 0;
+          if (!grub_errno)
+	    total += len;
+	}
+      return total;
+    }
+	  
   return grub_fshelp_read_file (node->data->disk, node,
 				read_hook, read_hook_data,
 				pos, len, buf, grub_ext2_read_block,
@@ -538,17 +676,28 @@ grub_ext2_read_file (grub_fshelp_node_t node,
 }
 
 
-/* Read the inode INO for the file described by DATA into INODE.  */
+/* Read the inode NODE->INO for the file described by NODE->DATA into NODE->INODE.  */
 static grub_err_t
-grub_ext2_read_inode (struct grub_ext2_data *data,
-		      int ino, struct grub_ext2_inode *inode)
+grub_ext2_read_inode (struct grub_fshelp_node *node)
 {
+  struct grub_ext2_data *data = node->data;
+  int ino = node->ino;
   struct grub_ext2_block_group blkgrp;
   struct grub_ext2_sblock *sblock = &data->sblock;
   int inodes_per_block;
   unsigned int blkno;
   unsigned int blkoff;
   grub_disk_addr_t base;
+  grub_uint8_t *full_inode;
+  grub_size_t full_isize;
+
+  if (node->inode_read)
+    return 0;
+
+  full_isize = EXT2_INODE_SIZE (data);
+  full_inode = grub_malloc (full_isize);
+  if (!full_inode)
+    return 0;
 
   /* It is easier to calculate if the first inode is 0.  */
   ino--;
@@ -557,9 +706,12 @@ grub_ext2_read_inode (struct grub_ext2_data *data,
                         ino / grub_le_to_cpu32 (sblock->inodes_per_group),
 			&blkgrp);
   if (grub_errno)
-    return grub_errno;
+    {
+      grub_free (full_inode);
+      return grub_errno;
+    }
 
-  inodes_per_block = EXT2_BLOCK_SIZE (data) / EXT2_INODE_SIZE (data);
+  inodes_per_block = EXT2_BLOCK_SIZE (data) / full_isize;
   blkno = (ino % grub_le_to_cpu32 (sblock->inodes_per_group))
     / inodes_per_block;
   blkoff = (ino % grub_le_to_cpu32 (sblock->inodes_per_group))
@@ -571,12 +723,18 @@ grub_ext2_read_inode (struct grub_ext2_data *data,
 	     << 32);
 
   /* Read the inode.  */
-  if (grub_disk_read (data->disk,
-		      ((base + blkno) << LOG2_EXT2_BLOCK_SIZE (data)),
-		      EXT2_INODE_SIZE (data) * blkoff,
-		      sizeof (struct grub_ext2_inode), inode))
-    return grub_errno;
+  node->inode_base = (base + blkno) << LOG2_EXT2_BLOCK_SIZE (data);
+  node->inode_offs = full_isize * blkoff;
+  if (grub_disk_read (data->disk, node->inode_base, node->inode_offs,
+		      full_isize, full_inode))
+    {
+      grub_free (full_inode);
+      return grub_errno;
+    }
+  grub_memcpy (&node->inode, full_inode, sizeof (struct grub_ext2_inode));
 
+  node->inode_read = 1;
+  grub_ext2_find_inline_data (node, full_isize, full_inode);
   return 0;
 }
 
@@ -632,11 +790,9 @@ grub_ext2_mount (grub_disk_t disk)
 
   data->diropen.data = data;
   data->diropen.ino = 2;
-  data->diropen.inode_read = 1;
-
   data->inode = &data->diropen.inode;
 
-  grub_ext2_read_inode (data, 2, data->inode);
+  grub_ext2_read_inode (&data->diropen);
   if (grub_errno)
     goto fail;
 
@@ -656,12 +812,9 @@ grub_ext2_read_symlink (grub_fshelp_node_t node)
   char *symlink;
   struct grub_fshelp_node *diro = node;
 
-  if (! diro->inode_read)
-    {
-      grub_ext2_read_inode (diro->data, diro->ino, &diro->inode);
-      if (grub_errno)
-	return 0;
-    }
+  grub_ext2_read_inode (diro);
+  if (grub_errno)
+    return 0;
 
   symlink = grub_malloc (grub_le_to_cpu32 (diro->inode.size) + 1);
   if (! symlink)
@@ -697,11 +850,42 @@ grub_ext2_iterate_dir (grub_fshelp_node_t dir,
   unsigned int fpos = 0;
   struct grub_fshelp_node *diro = (struct grub_fshelp_node *) dir;
 
-  if (! diro->inode_read)
+  grub_ext2_read_inode (diro);
+  if (grub_errno)
+    return 0;
+
+  /* Inline directory has only parent inode number and no explicit entries
+     for . or ..; simulate them */
+  if (diro->inline_offs)
     {
-      grub_ext2_read_inode (diro->data, diro->ino, &diro->inode);
+      struct grub_fshelp_node *dot, *dotdot;
+      grub_uint32_t inum;
+
+      dot = grub_malloc (sizeof (struct grub_fshelp_node));
+      if (!dot)
+	return 0;
+
+      dot->inode_read = 0;
+      dot->ino = dir->ino;
+      dot->data = diro->data;
+      if (hook (".", FILETYPE_DIRECTORY, dot, hook_data))
+	return 1;
+
+      /* First 4 bytes of inline directory data is parent inode number */
+      grub_ext2_read_file (diro, 0, 0, 0, EXT4_INLINE_DOTDOT_SIZE, (char *) &inum);
       if (grub_errno)
 	return 0;
+      dotdot = grub_malloc (sizeof (struct grub_fshelp_node));
+      if (!dotdot)
+	return 0;
+
+      dotdot->inode_read = 0;
+      dotdot->ino = grub_le_to_cpu32 (inum);
+      dotdot->data = diro->data;
+      if (hook ("..", FILETYPE_DIRECTORY, dotdot, hook_data))
+	return 1;
+
+      fpos = EXT4_INLINE_DOTDOT_SIZE;
     }
 
   /* Search the file.  */
@@ -752,17 +936,13 @@ grub_ext2_iterate_dir (grub_fshelp_node_t dir,
 	    {
 	      /* The filetype can not be read from the dirent, read
 		 the inode to get more information.  */
-	      grub_ext2_read_inode (diro->data,
-                                    grub_le_to_cpu32 (dirent.inode),
-				    &fdiro->inode);
+	      grub_ext2_read_inode (fdiro);
 	      if (grub_errno)
 		{
 		  grub_free (fdiro);
 		  return 0;
 		}
 
-	      fdiro->inode_read = 1;
-
 	      if ((grub_le_to_cpu16 (fdiro->inode.mode)
 		   & FILETYPE_INO_MASK) == FILETYPE_INO_DIRECTORY)
 		type = GRUB_FSHELP_DIR;
@@ -807,14 +987,11 @@ grub_ext2_open (struct grub_file *file, const char *name)
   if (err)
     goto fail;
 
-  if (! fdiro->inode_read)
-    {
-      err = grub_ext2_read_inode (data, fdiro->ino, &fdiro->inode);
-      if (err)
-	goto fail;
-    }
+  err = grub_ext2_read_inode (fdiro);
+  if (err)
+    goto fail;
 
-  grub_memcpy (data->inode, &fdiro->inode, sizeof (struct grub_ext2_inode));
+  grub_memcpy (&data->diropen, fdiro, sizeof (struct grub_fshelp_node));
   grub_free (fdiro);
 
   file->size = grub_le_to_cpu32 (data->inode->size);
@@ -873,13 +1050,9 @@ grub_ext2_dir_iter (const char *filename, enum grub_fshelp_filetype filetype,
   struct grub_dirhook_info info;
 
   grub_memset (&info, 0, sizeof (info));
-  if (! node->inode_read)
-    {
-      grub_ext2_read_inode (ctx->data, node->ino, &node->inode);
-      if (!grub_errno)
-	node->inode_read = 1;
-      grub_errno = GRUB_ERR_NONE;
-    }
+  grub_ext2_read_inode (node);
+  grub_errno = GRUB_ERR_NONE;
+
   if (node->inode_read)
     {
       info.mtimeset = 1;
-- 
tg: (ddda55c..) e/ext4 (depends on: master)
--
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