[EXT4 set 4][PATCH 3/5] i_version:ext4 inode version read/store

[EXT4 set 4][PATCH 3/5] i_version:ext4 inode version read/store

[Mingming Cao]

This patch adds 64-bit inode version support to ext4. The lower 32 bits
are stored in the osd1.linux1.l_i_version field while the high 32 bits
are stored in the i_version_hi field newly created in the ext4_inode.

Signed-off-by: Kalpak Shah <kalpak@clusterfs.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>

Index: linux-2.6.21/fs/ext4/inode.c
===================================================================
--- linux-2.6.21.orig/fs/ext4/inode.c
+++ linux-2.6.21/fs/ext4/inode.c
@@ -2709,6 +2709,13 @@ void ext4_read_inode(struct inode * inod
 	EXT4_INODE_GET_XTIME(i_atime, inode, raw_inode);
 	EXT4_EINODE_GET_XTIME(i_crtime, ei, raw_inode);

+	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))
+			inode->i_version |=
+			(__u64)(le32_to_cpu(raw_inode->i_version_hi)) << 32;
+	}
+
 	if (S_ISREG(inode->i_mode)) {
 		inode->i_op = &ext4_file_inode_operations;
 		inode->i_fop = &ext4_file_operations;
@@ -2852,8 +2859,14 @@ static int ext4_do_update_inode(handle_t
 	} else for (block = 0; block < EXT4_N_BLOCKS; block++)
 		raw_inode->i_block[block] = ei->i_data[block];

-	if (ei->i_extra_isize)
+	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)) {
+			raw_inode->i_version_hi =
+				cpu_to_le32(inode->i_version >> 32);
+		}
 		raw_inode->i_extra_isize = cpu_to_le16(ei->i_extra_isize);
+	}

 	BUFFER_TRACE(bh, "call ext4_journal_dirty_metadata");
 	rc = ext4_journal_dirty_metadata(handle, bh);
Index: linux-2.6.21/include/linux/ext4_fs.h
===================================================================
--- linux-2.6.21.orig/include/linux/ext4_fs.h
+++ linux-2.6.21/include/linux/ext4_fs.h
@@ -297,7 +297,7 @@ struct ext4_inode {
 	__le32	i_flags;	/* File flags */
 	union {
 		struct {
-			__u32  l_i_reserved1;
+			__u32  l_i_version;
 		} linux1;
 		struct {
 			__u32  h_i_translator;
@@ -406,6 +406,8 @@ do {									       \
 				       raw_inode->xtime ## _extra);	       \
 } while (0)

+#define i_disk_version osd1.linux1.l_i_version
+
 #if defined(__KERNEL__) || defined(__linux__)
 #define i_reserved1	osd1.linux1.l_i_reserved1
 #define i_frag		osd2.linux2.l_i_frag

Re: [EXT4 set 4][PATCH 3/5] i_version:ext4 inode version read/store

[Andrew Morton]

On Sun, 01 Jul 2007 03:37:36 -0400
Mingming Cao <cmm@us.ibm.com> wrote:

> This patch adds 64-bit inode version support to ext4. The lower 32 bits
> are stored in the osd1.linux1.l_i_version field while the high 32 bits
> are stored in the i_version_hi field newly created in the ext4_inode.

So reading the code here does serve to answer the question I raised against
the earlier patch.  A bit.

I'd have thought that this patch and the one which adds i_version_hi should
be folded into a single diff?

> 
> Index: linux-2.6.21/fs/ext4/inode.c
> ===================================================================
> --- linux-2.6.21.orig/fs/ext4/inode.c
> +++ linux-2.6.21/fs/ext4/inode.c
> @@ -2709,6 +2709,13 @@ void ext4_read_inode(struct inode * inod
>  	EXT4_INODE_GET_XTIME(i_atime, inode, raw_inode);
>  	EXT4_EINODE_GET_XTIME(i_crtime, ei, raw_inode);
> 
> +	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))
> +			inode->i_version |=
> +			(__u64)(le32_to_cpu(raw_inode->i_version_hi)) << 32;

<checks the precedence of "(type)" versus "<<">

<OK>

> +	}

I don't quite see how the above two tests are sufficient to unambiguously
determine that the i_version_hi field is present on-disk.

I guess we're implicitly assuming that if the on-disk inode is big enough
then it _must_ have i_version_hi in there?  If so, why is the comparison
with EXT4_GOOD_OLD_INODE_SIZE needed?

Some description of the overall approach to inode version identification
would be helpful here.

>  	if (S_ISREG(inode->i_mode)) {
>  		inode->i_op = &ext4_file_inode_operations;
>  		inode->i_fop = &ext4_file_operations;
> @@ -2852,8 +2859,14 @@ static int ext4_do_update_inode(handle_t
>  	} else for (block = 0; block < EXT4_N_BLOCKS; block++)
>  		raw_inode->i_block[block] = ei->i_data[block];
> 
> -	if (ei->i_extra_isize)
> +	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)) {

There's no comparison with EXT4_GOOD_OLD_INODE_SIZE here...

> +			raw_inode->i_version_hi =
> +				cpu_to_le32(inode->i_version >> 32);
> +		}
>  		raw_inode->i_extra_isize = cpu_to_le16(ei->i_extra_isize);
> +	}
> 

Re: [EXT4 set 4][PATCH 3/5] i_version:ext4 inode version read/store

[Andreas Dilger]

On Jul 10, 2007  16:31 -0700, Andrew Morton wrote:
> > This patch adds 64-bit inode version support to ext4. The lower 32 bits
> > are stored in the osd1.linux1.l_i_version field while the high 32 bits
> > are stored in the i_version_hi field newly created in the ext4_inode.
> 
> So reading the code here does serve to answer the question I raised against
> the earlier patch.  A bit.
> 
> I'd have thought that this patch and the one which adds i_version_hi should
> be folded into a single diff?

It could be - the original patch to reserve i_version_hi was submitted to
before the patches were ready to avoid that space being used by something
else.

> > +	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
> > +		if (EXT4_FITS_IN_INODE(raw_inode, ei, i_version_hi))
> > +			inode->i_version |=
> > +			(__u64)(le32_to_cpu(raw_inode->i_version_hi)) << 32;
> 
> <checks the precedence of "(type)" versus "<<">
> 
> <OK>
> 
> > +	}
> 
> I don't quite see how the above two tests are sufficient to unambiguously
> determine that the i_version_hi field is present on-disk.
> 
> I guess we're implicitly assuming that if the on-disk inode is big enough
> then it _must_ have i_version_hi in there?  If so, why is the comparison
> with EXT4_GOOD_OLD_INODE_SIZE needed?

The GOOT_OLD_INODE_SIZE check is needed to know if i_extra_isize is even
present or valid in the on-disk inode.

> > @@ -2852,8 +2859,14 @@ static int ext4_do_update_inode(handle_t
> > +	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)) {
> 
> There's no comparison with EXT4_GOOD_OLD_INODE_SIZE here...

Because this is the in-memory version and it is always valid (set to zero
if there is extra space in the on-disk inode).

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.