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bz 450641 try2 - fix gfs2 block allocation (cleaned up)

PATCH New Benjamin Marzinski 1 participant 1 message Jun 24, 2008 GFS2 file system

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Benjamin Marzinski

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PATCH 1/1 bz 450641 try2 - fix gfs2 block allocation (cleaned up)

This patch fixes bz 450641.

This patch changes the computation for zero_metapath_length(), which it renames to metapath_branch_start(). When you are extending the metadata tree, The indirect blocks that point to the new data block must either diverge from the existing tree either at the inode, or at the first indirect block. They can diverge at the first indirect block because the inode has room for 483 pointers while the indirect blocks have room for 509 pointers, so when the tree is grown, there is some free space in the first indirect block. What metapath_branch_start() now computes is the height where the first indirect block for the new data block is located. It can either be 1 (if the indirect block diverges from the inode) or 2 (if it diverges from the first indirect block).

This patch is the same as the last one, plus some cosmetic changes.

-Ben

Signed-off-by Benjamin Marzinski <[email protected]>
---
 bmap.c |   23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

-------------- next part --------------

fs/gfs2/bmap.c +9 -14
Index: gfs2-2.6-nmw-patched/fs/gfs2/bmap.c
===================================================================
@@ -246,15 +246,11 @@ static void find_metapath(const struct g
 
 }
 
-static inline unsigned int zero_metapath_length(const struct metapath *mp,
-						unsigned height)
+static inline unsigned int metapath_branch_start(const struct metapath *mp)
 {
-	unsigned int i;
-	for (i = 0; i < height - 1; i++) {
-		if (mp->mp_list[i] != 0)
-			return i;
-	}
-	return height;
+	if (mp->mp_list[0] == 0)
+		return 2;
+	return 1;
 }
 
 /**

@@ -436,7 +432,7 @@ static int gfs2_bmap_alloc(struct inode 
 	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct buffer_head *dibh = mp->mp_bh[0];
 	u64 bn, dblock = 0;
-	unsigned n, i, blks, alloced = 0, iblks = 0, zmpl = 0;
+	unsigned n, i, blks, alloced = 0, iblks = 0, branch_start = 0;
 	unsigned dblks = 0;
 	unsigned ptrs_per_blk;
 	const unsigned end_of_metadata = height - 1;

@@ -471,9 +467,8 @@ static int gfs2_bmap_alloc(struct inode 
 			/* Building up tree height */
 			state = ALLOC_GROW_HEIGHT;
 			iblks = height - ip->i_height;
-			zmpl = zero_metapath_length(mp, height);
-			iblks -= zmpl;
-			iblks += height;
+			branch_start = metapath_branch_start(mp);
+			iblks += (height - branch_start);
 		}
 	}
 

@@ -509,13 +504,13 @@ static int gfs2_bmap_alloc(struct inode 
 					sizeof(struct gfs2_meta_header));
 				*ptr = zero_bn;
 				state = ALLOC_GROW_DEPTH;
-				for(i = zmpl; i < height; i++) {
+				for(i = branch_start; i < height; i++) {
 					if (mp->mp_bh[i] == NULL)
 						break;
 					brelse(mp->mp_bh[i]);
 					mp->mp_bh[i] = NULL;
 				}
-				i = zmpl;
+				i = branch_start;
 			}
 			if (n == 0)
 				break;