Patchwork [09/51] libext2fs: Create the inode bitmap checksum

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Submitter Darrick J. Wong
Date Dec. 14, 2011, 1:14 a.m.
Message ID <20111214011415.20947.77748.stgit@elm3c44.beaverton.ibm.com>
Download mbox | patch
Permalink /patch/131243/
State Superseded
Headers show

Comments

Darrick J. Wong - Dec. 14, 2011, 1:14 a.m.
Provide a field in the block group descriptor to store inode bitmap checksum,
and some helper functions to calculate and verify it.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
 lib/ext2fs/blknum.c       |   15 +++++++++++++++
 lib/ext2fs/closefs.c      |   29 +++++++++++++++++------------
 lib/ext2fs/csum.c         |   44 ++++++++++++++++++++++++++++++++++++++++++++
 lib/ext2fs/ext2_err.et.in |    3 +++
 lib/ext2fs/ext2_fs.h      |    4 ++++
 lib/ext2fs/ext2fs.h       |    6 ++++++
 lib/ext2fs/rw_bitmaps.c   |   16 ++++++++++++++++
 7 files changed, 105 insertions(+), 12 deletions(-)



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Darrick J. Wong - Dec. 19, 2011, 8:03 p.m.
On Sun, Dec 18, 2011 at 07:18:20AM -0700, Andreas Dilger wrote:
> On 2011-12-13, at 18:14, "Darrick J. Wong" <djwong@us.ibm.com> wrote:
> > Provide a field in the block group descriptor to store inode bitmap checksum,
> > and some helper functions to calculate and verify it.
> > +int ext2fs_inode_bitmap_csum_verify(ext2_filsys fs, dgrp_t group,
> > +                    char *bitmap, int size)
> > +{
> > +    struct ext4_group_desc *gdp = (struct ext4_group_desc *)
> > +            ext2fs_group_desc(fs, fs->group_desc, group);
> > +    __u32 provided, calculated;
> > +
> > +    if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
> > +                    EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
> > +        return 1;
> > +    provided = gdp->bg_inode_bitmap_csum_lo;
> > +    calculated = ext2fs_crc32c_le(~0, fs->super->s_uuid,
> > +                      sizeof(fs->super->s_uuid));
> 
> It makes sense to precompute the uuid checksum and store it in the
> ext2_filsys struct so that it is accessible everywhere, like is done in the
> kernel.

I wonder how much that'll help compared to the IO overhead, but I suppose every
bit helps.

> > +    calculated = ext2fs_crc32c_le(calculated, (unsigned char *)bitmap,
> > +                      size);
> > +    if (fs->super->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_LOCATION)
> > +        provided |= (__u32)gdp->bg_inode_bitmap_csum_hi << 16;
> > +    else
> > +        calculated &= 0xFFFF;
> > +
> > +    return provided == calculated;
> > +}
> > +
> > 
> > +++ b/lib/ext2fs/ext2_fs.h
> > @@ -191,6 +191,10 @@ struct ext4_group_desc
> >    __u32    bg_reserved;
> > };
> > 
> > +#define EXT4_BG_INODE_BITMAP_CSUM_HI_LOCATION    \
> > +    (offsetof(struct ext4_group_desc, bg_inode_bitmap_csum_hi) + \
> > +     sizeof(__u16))
> 
> It is a bit misleading to call this constant the "location" since it is
> actually the end of the csum_hi field.  Either the sizeof(__u16) should be
> moved to the caller, or this should be renamed to
> EXT4_BG_INODE_BITMAP_CSUM_HI_END or similar. 

Ok.

--D

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Patch

diff --git a/lib/ext2fs/blknum.c b/lib/ext2fs/blknum.c
index 33da7d6..190242c 100644
--- a/lib/ext2fs/blknum.c
+++ b/lib/ext2fs/blknum.c
@@ -230,6 +230,21 @@  void ext2fs_block_bitmap_loc_set(ext2_filsys fs, dgrp_t group, blk64_t blk)
 }
 
 /*
+ * Return the inode bitmap checksum of a group
+ */
+__u32 ext2fs_inode_bitmap_checksum(ext2_filsys fs, dgrp_t group)
+{
+	struct ext4_group_desc *gdp;
+	__u32 csum;
+
+	gdp = ext4fs_group_desc(fs, fs->group_desc, group);
+	csum = gdp->bg_inode_bitmap_csum_lo;
+	if (fs->super->s_desc_size < EXT4_BG_INODE_BITMAP_CSUM_HI_LOCATION)
+		csum |= ((__u32)gdp->bg_inode_bitmap_csum_hi << 16);
+	return csum;
+}
+
+/*
  * Return the inode bitmap block of a group
  */
 blk64_t ext2fs_inode_bitmap_loc(ext2_filsys fs, dgrp_t group)
diff --git a/lib/ext2fs/closefs.c b/lib/ext2fs/closefs.c
index 973c2a2..1867be3 100644
--- a/lib/ext2fs/closefs.c
+++ b/lib/ext2fs/closefs.c
@@ -288,6 +288,23 @@  errcode_t ext2fs_flush2(ext2_filsys fs, int flags)
 
 	fs->super->s_wtime = fs->now ? fs->now : time(NULL);
 	fs->super->s_block_group_nr = 0;
+
+	/*
+	 * If the write_bitmaps() function is present, call it to
+	 * flush the bitmaps.  This is done this way so that a simple
+	 * program that doesn't mess with the bitmaps doesn't need to
+	 * drag in the bitmaps.c code.
+	 *
+	 * Bitmap checksums live in the group descriptor, so the
+	 * bitmaps need to be written before the descriptors.
+	 */
+	if (fs->write_bitmaps) {
+		retval = fs->write_bitmaps(fs);
+		if (retval)
+			goto errout;
+	}
+
+	/* Prepare the group descriptors for writing */
 #ifdef WORDS_BIGENDIAN
 	retval = EXT2_ET_NO_MEMORY;
 	retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &super_shadow);
@@ -378,18 +395,6 @@  errcode_t ext2fs_flush2(ext2_filsys fs, int flags)
 
 	ext2fs_numeric_progress_close(fs, &progress, NULL);
 
-	/*
-	 * If the write_bitmaps() function is present, call it to
-	 * flush the bitmaps.  This is done this way so that a simple
-	 * program that doesn't mess with the bitmaps doesn't need to
-	 * drag in the bitmaps.c code.
-	 */
-	if (fs->write_bitmaps) {
-		retval = fs->write_bitmaps(fs);
-		if (retval)
-			goto errout;
-	}
-
 write_primary_superblock_only:
 	/*
 	 * Write out master superblock.  This has to be done
diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
index 1f7c641..47c1111 100644
--- a/lib/ext2fs/csum.c
+++ b/lib/ext2fs/csum.c
@@ -30,6 +30,50 @@ 
 #define STATIC static
 #endif
 
+int ext2fs_inode_bitmap_csum_verify(ext2_filsys fs, dgrp_t group,
+				    char *bitmap, int size)
+{
+	struct ext4_group_desc *gdp = (struct ext4_group_desc *)
+			ext2fs_group_desc(fs, fs->group_desc, group);
+	__u32 provided, calculated;
+
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 1;
+	provided = gdp->bg_inode_bitmap_csum_lo;
+	calculated = ext2fs_crc32c_le(~0, fs->super->s_uuid,
+				      sizeof(fs->super->s_uuid));
+	calculated = ext2fs_crc32c_le(calculated, (unsigned char *)bitmap,
+				      size);
+	if (fs->super->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_LOCATION)
+		provided |= (__u32)gdp->bg_inode_bitmap_csum_hi << 16;
+	else
+		calculated &= 0xFFFF;
+
+	return provided == calculated;
+}
+
+errcode_t ext2fs_inode_bitmap_csum_set(ext2_filsys fs, dgrp_t group,
+				       char *bitmap, int size)
+{
+	__u32 crc;
+	struct ext4_group_desc *gdp = (struct ext4_group_desc *)
+			ext2fs_group_desc(fs, fs->group_desc, group);
+
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 0;
+
+	crc = ext2fs_crc32c_le(~0, fs->super->s_uuid,
+			       sizeof(fs->super->s_uuid));
+	crc = ext2fs_crc32c_le(crc, (unsigned char *)bitmap, size);
+	gdp->bg_inode_bitmap_csum_lo = crc & 0xFFFF;
+	if (fs->super->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_LOCATION)
+		gdp->bg_inode_bitmap_csum_hi = crc >> 16;
+
+	return 0;
+}
+
 static errcode_t ext2fs_inode_csum(ext2_filsys fs, ext2_ino_t inum,
 			       struct ext2_inode_large *inode,
 			       __u32 *crc, int has_hi)
diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
index d4a5b10..3f5d08f 100644
--- a/lib/ext2fs/ext2_err.et.in
+++ b/lib/ext2fs/ext2_err.et.in
@@ -446,4 +446,7 @@  ec	EXT2_ET_MMP_OPEN_DIRECT,
 ec	EXT2_ET_INODE_CSUM_INVALID,
 	"Inode checksum does not match inode"
 
+ec	EXT2_ET_INODE_BITMAP_CSUM_INVALID,
+	"Inode bitmap checksum does not match bitmap"
+
 	end
diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h
index 4bcf1de..70b9fa2 100644
--- a/lib/ext2fs/ext2_fs.h
+++ b/lib/ext2fs/ext2_fs.h
@@ -191,6 +191,10 @@  struct ext4_group_desc
 	__u32	bg_reserved;
 };
 
+#define EXT4_BG_INODE_BITMAP_CSUM_HI_LOCATION	\
+	(offsetof(struct ext4_group_desc, bg_inode_bitmap_csum_hi) + \
+	 sizeof(__u16))
+
 #define EXT2_BG_INODE_UNINIT	0x0001 /* Inode table/bitmap not initialized */
 #define EXT2_BG_BLOCK_UNINIT	0x0002 /* Block bitmap not initialized */
 #define EXT2_BG_INODE_ZEROED	0x0004 /* On-disk itable initialized to zero */
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 822cf78..3a07f4a 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -797,6 +797,7 @@  extern errcode_t ext2fs_get_block_bitmap_range2(ext2fs_block_bitmap bmap,
 					 void *out);
 
 /* blknum.c */
+extern __u32 ext2fs_inode_bitmap_checksum(ext2_filsys fs, dgrp_t group);
 extern dgrp_t ext2fs_group_of_blk2(ext2_filsys fs, blk64_t);
 extern blk64_t ext2fs_group_first_block2(ext2_filsys fs, dgrp_t group);
 extern blk64_t ext2fs_group_last_block2(ext2_filsys fs, dgrp_t group);
@@ -827,6 +828,7 @@  extern struct ext2_group_desc *ext2fs_group_desc(ext2_filsys fs,
 extern blk64_t ext2fs_block_bitmap_loc(ext2_filsys fs, dgrp_t group);
 extern void ext2fs_block_bitmap_loc_set(ext2_filsys fs, dgrp_t group,
 					blk64_t blk);
+extern __u32 ext2fs_inode_bitmap_csum(ext2_filsys fs, dgrp_t group);
 extern blk64_t ext2fs_inode_bitmap_loc(ext2_filsys fs, dgrp_t group);
 extern void ext2fs_inode_bitmap_loc_set(ext2_filsys fs, dgrp_t group,
 					blk64_t blk);
@@ -936,6 +938,10 @@  extern __u32 ext2fs_crc32c_be(__u32 crc, unsigned char const *p, size_t len);
 extern __u32 ext2fs_crc32c_le(__u32 crc, unsigned char const *p, size_t len);
 
 /* csum.c */
+extern errcode_t ext2fs_inode_bitmap_csum_set(ext2_filsys fs, dgrp_t group,
+					      char *bitmap, int size);
+extern int ext2fs_inode_bitmap_csum_verify(ext2_filsys fs, dgrp_t group,
+					   char *bitmap, int size);
 extern errcode_t ext2fs_inode_csum_set(ext2_filsys fs, ext2_ino_t inum,
 				       struct ext2_inode_large *inode);
 extern int ext2fs_inode_csum_verify(ext2_filsys fs, ext2_ino_t inum,
diff --git a/lib/ext2fs/rw_bitmaps.c b/lib/ext2fs/rw_bitmaps.c
index 1d5f7b2..0ad5eb1 100644
--- a/lib/ext2fs/rw_bitmaps.c
+++ b/lib/ext2fs/rw_bitmaps.c
@@ -117,6 +117,12 @@  static errcode_t write_bitmaps(ext2_filsys fs, int do_inode, int do_block)
 		if (retval)
 			goto errout;
 
+		retval = ext2fs_inode_bitmap_csum_set(fs, i, inode_buf,
+						      inode_nbytes);
+		if (retval)
+			goto errout;
+		ext2fs_group_desc_csum_set(fs, i);
+
 		blk = ext2fs_inode_bitmap_loc(fs, i);
 		if (blk) {
 			retval = io_channel_write_blk64(fs->io, blk, 1,
@@ -288,6 +294,16 @@  static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
 					retval = EXT2_ET_INODE_BITMAP_READ;
 					goto cleanup;
 				}
+
+				/* verify inode bitmap checksum */
+				if (!(fs->flags &
+				      EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
+				    !ext2fs_inode_bitmap_csum_verify(fs, i,
+						inode_bitmap, inode_nbytes)) {
+					retval =
+					EXT2_ET_INODE_BITMAP_CSUM_INVALID;
+					goto cleanup;
+				}
 			} else
 				memset(inode_bitmap, 0, inode_nbytes);
 			cnt = inode_nbytes << 3;