[XFS] remove i_gen from incore inode

i_gen is incremented in directory operations when the
directory is changed. It is never read or otherwise used
so it should be removed to help reduce the size of the
struct xfs_inode.

The patch also removes a duplicate logging of the directory
inode core. We only need to do this once per transaction
so kill the one associated with the i_gen increment.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Niv Sardi <xaiki@sgi.com>

fs/xfs/xfs_inode.h

@@ -261,7 +261,6 @@ typedef struct xfs_inode {
 	unsigned short		i_flags;	/* see defined flags below */
 	unsigned char		i_update_core;	/* timestamps/size is dirty */
 	unsigned char		i_update_size;	/* di_size field is dirty */
-	unsigned int		i_gen;		/* generation count */
 	unsigned int		i_delayed_blks;	/* count of delay alloc blks */
 
 	xfs_icdinode_t		i_d;		/* most of ondisk inode */

fs/xfs/xfs_rename.c

@@ -367,19 +367,11 @@ xfs_rename(
 					&first_block, &free_list, spaceres);
 	if (error)
 		goto abort_return;
-	xfs_ichgtime(src_dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 
-	/*
-	 * Update the generation counts on all the directory inodes
-	 * that we're modifying.
-	 */
-	src_dp->i_gen++;
+	xfs_ichgtime(src_dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 	xfs_trans_log_inode(tp, src_dp, XFS_ILOG_CORE);
-
-	if (new_parent) {
-		target_dp->i_gen++;
+	if (new_parent)
 		xfs_trans_log_inode(tp, target_dp, XFS_ILOG_CORE);
-	}
 
 	/*
 	 * If this is a synchronous mount, make sure that the

fs/xfs/xfs_vnodeops.c

@@ -1599,8 +1599,6 @@ xfs_create(
 		xfs_trans_set_sync(tp);
 	}
 
-	dp->i_gen++;
-
 	/*
 	 * Attach the dquot(s) to the inodes and modify them incore.
 	 * These ids of the inode couldn't have changed since the new
@@ -1967,13 +1965,6 @@ xfs_remove(
 	}
 	xfs_ichgtime(dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 
-	/*
-	 * Bump the in memory generation count on the parent
-	 * directory so that other can know that it has changed.
-	 */
-	dp->i_gen++;
-	xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
-
 	if (is_dir) {
 		/*
 		 * Drop the link from ip's "..".
@@ -1991,8 +1982,8 @@ xfs_remove(
 	} else {
 		/*
 		 * When removing a non-directory we need to log the parent
-		 * inode here for the i_gen update.  For a directory this is
-		 * done implicitly by the xfs_droplink call for the ".." entry.
+		 * inode here.  For a directory this is done implicitly
+		 * by the xfs_droplink call for the ".." entry.
 		 */
 		xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 	}
@@ -2152,7 +2143,6 @@ xfs_link(
 	if (error)
 		goto abort_return;
 	xfs_ichgtime(tdp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
-	tdp->i_gen++;
 	xfs_trans_log_inode(tp, tdp, XFS_ILOG_CORE);
 
 	error = xfs_bumplink(tp, sip);
@@ -2329,18 +2319,10 @@ xfs_mkdir(
 	}
 	xfs_ichgtime(dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 
-	/*
-	 * Bump the in memory version number of the parent directory
-	 * so that other processes accessing it will recognize that
-	 * the directory has changed.
-	 */
-	dp->i_gen++;
-
 	error = xfs_dir_init(tp, cdp, dp);
 	if (error)
 		goto error2;
 
-	cdp->i_gen = 1;
 	error = xfs_bumplink(tp, dp);
 	if (error)
 		goto error2;
@@ -2626,13 +2608,6 @@ xfs_symlink(
 	xfs_ichgtime(dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 	xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 
-	/*
-	 * Bump the in memory version number of the parent directory
-	 * so that other processes accessing it will recognize that
-	 * the directory has changed.
-	 */
-	dp->i_gen++;
-
 	/*
 	 * If this is a synchronous mount, make sure that the
 	 * symlink transaction goes to disk before returning to