[PATCH 1/2] e2fsck: Discard only unused parts of inode table

[Lukas Czerner <lczerner@redhat.com>]

When calling e2fsck with '-E discard' option it might happen that
valid inodes are discarded accidentally. This is because we just
discard the part of inode table which lies past the highest used
inode. This is terribly wrong (sorry!).

This patch fixes it so only the free parts of an inode table
is discarded, leaving used inodes intact. This was tested with highly
fragmented inode tables with block size 4k and 1k.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reported-by: Phillip Susi <psusi@ubuntu.com>
---
 e2fsck/pass5.c |   59 +++++++++++++++++++++++++++++++++++--------------------
 1 files changed, 37 insertions(+), 22 deletions(-)

diff --git a/e2fsck/pass5.c b/e2fsck/pass5.c
index 1e836e3..9cc4a20 100644
--- a/e2fsck/pass5.c
+++ b/e2fsck/pass5.c
@@ -94,6 +94,26 @@ static void e2fsck_discard_blocks(e2fsck_t ctx, io_manager manager,
 		ctx->options &= ~E2F_OPT_DISCARD;
 }
 
+static void e2fsck_discard_inodes(e2fsck_t ctx, int group,
+				  int start, int count)
+{
+	ext2_filsys fs = ctx->fs;
+	blk64_t blk, num;
+
+	/*
+	 * We can discard only blocks containing only unused
+	 * inodes in the table.
+	 */
+	blk = DIV_ROUND_UP(start,
+		EXT2_INODES_PER_BLOCK(fs->super));
+	count -= (blk * EXT2_INODES_PER_BLOCK(fs->super) - start);
+	blk += ext2fs_inode_table_loc(fs, group);
+	num = count / EXT2_INODES_PER_BLOCK(fs->super);
+
+	if (num > 0)
+		e2fsck_discard_blocks(ctx, fs->io->manager, blk, num);
+}
+
 #define NO_BLK ((blk64_t) -1)
 
 static void print_bitmap_problem(e2fsck_t ctx, int problem,
@@ -422,6 +442,7 @@ static void check_inode_bitmaps(e2fsck_t ctx)
 	ext2_ino_t	i;
 	unsigned int	free_inodes = 0;
 	int		group_free = 0;
+	int		first_free = fs->super->s_inodes_per_group;
 	int		dirs_count = 0;
 	int		group = 0;
 	unsigned int	inodes = 0;
@@ -497,6 +518,7 @@ redo_counts:
 				 * are 0, count the free inode,
 				 * skip the current block group.
 				 */
+				first_free = 0;
 				inodes = fs->super->s_inodes_per_group - 1;
 				group_free = inodes;
 				free_inodes += inodes;
@@ -561,37 +583,27 @@ redo_counts:
 		ctx->options &= ~E2F_OPT_DISCARD;
 
 do_counts:
+		inodes++;
 		if (bitmap) {
 			if (ext2fs_test_inode_bitmap2(ctx->inode_dir_map, i))
 				dirs_count++;
+			if (inodes - 1 > first_free) {
+				e2fsck_discard_inodes(ctx, group, first_free,
+						      inodes - first_free - 1);
+				first_free = fs->super->s_inodes_per_group;
+			}
 		} else if (!skip_group || csum_flag) {
 			group_free++;
 			free_inodes++;
+			if (first_free > inodes)
+				first_free = inodes;
 		}
 
-		inodes++;
 		if ((inodes == fs->super->s_inodes_per_group) ||
 		    (i == fs->super->s_inodes_count)) {
-
-			free_array[group] = group_free;
-			dir_array[group] = dirs_count;
-
-			/* Discard inode table */
-			if (ctx->options & E2F_OPT_DISCARD) {
-				blk64_t used_blks, blk, num;
-
-				used_blks = DIV_ROUND_UP(
-					(EXT2_INODES_PER_GROUP(fs->super) -
-					group_free),
-					EXT2_INODES_PER_BLOCK(fs->super));
-
-				blk = ext2fs_inode_table_loc(fs, group) +
-				      used_blks;
-				num = fs->inode_blocks_per_group -
-				      used_blks;
-				e2fsck_discard_blocks(ctx, manager, blk, num);
-			}
-
+			if (inodes - 1 > first_free)
+				e2fsck_discard_inodes(ctx, group, first_free,
+						      inodes - first_free - 1);
 			/*
 			 * If discard zeroes data and the group inode table
 			 * was not zeroed yet, set itable as zeroed
@@ -599,12 +611,15 @@ do_counts:
 			if ((ctx->options & E2F_OPT_DISCARD) &&
 			    (io_channel_discard_zeroes_data(fs->io)) &&
 			    !(ext2fs_bg_flags_test(fs, group,
-						  EXT2_BG_INODE_ZEROED))) {
+						   EXT2_BG_INODE_ZEROED))) {
 				ext2fs_bg_flags_set(fs, group,
 						    EXT2_BG_INODE_ZEROED);
 				ext2fs_group_desc_csum_set(fs, group);
 			}
 
+			first_free = fs->super->s_inodes_per_group;
+			free_array[group] = group_free;
+			dir_array[group] = dirs_count;
 			group ++;
 			inodes = 0;
 			skip_group = 0;
-- 
1.7.4.4