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Date: Thu, 13 Sep 2012 18:49:17 -0400
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>
Subject: [PATCH 2/5] resize2fs: fix overhead calculation for meta_bg file systems
The file system overhead calculation in calculate_minimum_resize_size
was incorrect meta_bg file systems. This caused the minimum size to
underflow for very large file systems, which threw resize2fs into a
loop generally lasted longer than the user's patience.
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
resize/resize2fs.c | 77 +++++++++++++++++++++++++++++++-----------------------
1 file changed, 45 insertions(+), 32 deletions(-)
diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index dc2805d..85de144 100644
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -62,10 +62,6 @@ static errcode_t fix_sb_journal_backup(ext2_filsys fs);
((blk) < (ext2fs_inode_table_loc((fs), (i)) + \
(fs)->inode_blocks_per_group)))
-#define META_OVERHEAD(fs) (2 + (fs)->inode_blocks_per_group)
-#define SUPER_OVERHEAD(fs) (1 + (fs)->desc_blocks +\
- (fs)->super->s_reserved_gdt_blocks)
-
/*
* This is the top-level routine which does the dirty deed....
*/
@@ -1880,6 +1876,27 @@ static errcode_t fix_sb_journal_backup(ext2_filsys fs)
return 0;
}
+static int calc_group_overhead(ext2_filsys fs, blk64_t grp,
+ int old_desc_blocks)
+{
+ blk64_t super_blk, old_desc_blk, new_desc_blk;
+ int overhead;
+
+ /* inode table blocks plus allocation bitmaps */
+ overhead = fs->inode_blocks_per_group + 2;
+
+ ext2fs_super_and_bgd_loc2(fs, grp, &super_blk,
+ &old_desc_blk, &new_desc_blk, 0);
+ if ((grp == 0) || super_blk)
+ overhead++;
+ if (old_desc_blk)
+ overhead += old_desc_blocks;
+ else if (new_desc_blk)
+ overhead++;
+ return overhead;
+}
+
+
/*
* calcluate the minimum number of blocks the given fs can be resized to
*/
@@ -1890,6 +1907,8 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
blk64_t grp, data_needed, last_start;
blk64_t overhead = 0;
int num_of_superblocks = 0;
+ blk64_t super_overhead = 0;
+ int old_desc_blocks;
int extra_groups = 0;
int flexbg_size = 1 << fs->super->s_log_groups_per_flex;
@@ -1906,28 +1925,29 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
EXT2_BLOCKS_PER_GROUP(fs->super));
/*
- * we need to figure out how many backup superblocks we have so we can
- * account for that in the metadata
+ * number of old-style block group descriptor blocks
*/
- for (grp = 0; grp < fs->group_desc_count; grp++) {
- if (ext2fs_bg_has_super(fs, grp))
- num_of_superblocks++;
- }
+ if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
+ old_desc_blocks = fs->super->s_first_meta_bg;
+ else
+ old_desc_blocks = fs->desc_blocks +
+ fs->super->s_reserved_gdt_blocks;
/* calculate how many blocks are needed for data */
data_needed = ext2fs_blocks_count(fs->super) -
ext2fs_free_blocks_count(fs->super);
- data_needed -= SUPER_OVERHEAD(fs) * num_of_superblocks;
- data_needed -= META_OVERHEAD(fs) * fs->group_desc_count;
+ for (grp = 0; grp < fs->group_desc_count; grp++)
+ data_needed -= calc_group_overhead(fs, grp, old_desc_blocks);
+
+ /*
+ * For ext4 we need to allow for up to a flex_bg worth of
+ * inode tables of slack space so the resize operation can be
+ * guaranteed to finish.
+ */
if (fs->super->s_feature_incompat & EXT4_FEATURE_INCOMPAT_FLEX_BG) {
- /*
- * For ext4 we need to allow for up to a flex_bg worth
- * of inode tables of slack space so the resize
- * operation can be guaranteed to finish.
- */
extra_groups = flexbg_size - (groups & (flexbg_size - 1));
- data_needed += META_OVERHEAD(fs) * extra_groups;
+ data_needed += fs->inode_blocks_per_group * extra_groups;
extra_groups = groups % flexbg_size;
}
@@ -1938,10 +1958,7 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
data_blocks = groups * EXT2_BLOCKS_PER_GROUP(fs->super);
last_start = 0;
for (grp = 0; grp < groups; grp++) {
- overhead = META_OVERHEAD(fs);
-
- if (ext2fs_bg_has_super(fs, grp))
- overhead += SUPER_OVERHEAD(fs);
+ overhead = calc_group_overhead(fs, grp, old_desc_blocks);
/*
* we want to keep track of how much data we can store in
@@ -1970,15 +1987,12 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
data_blocks += extra_grps * EXT2_BLOCKS_PER_GROUP(fs->super);
/* ok we have to account for the last group */
- overhead = META_OVERHEAD(fs);
- if (ext2fs_bg_has_super(fs, groups-1))
- overhead += SUPER_OVERHEAD(fs);
+ overhead = calc_group_overhead(fs, groups-1, old_desc_blocks);
last_start += EXT2_BLOCKS_PER_GROUP(fs->super) - overhead;
for (grp = groups; grp < groups+extra_grps; grp++) {
- overhead = META_OVERHEAD(fs);
- if (ext2fs_bg_has_super(fs, grp))
- overhead += SUPER_OVERHEAD(fs);
+ overhead = calc_group_overhead(fs, grp,
+ old_desc_blocks);
/*
* again, we need to see how much data we cram into
@@ -2003,13 +2017,14 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
*/
extra_groups = flexbg_size -
(groups & (flexbg_size - 1));
- data_needed += META_OVERHEAD(fs) * extra_groups;
+ data_needed += (fs->inode_blocks_per_group *
+ extra_groups);
extra_groups = groups % flexbg_size;
}
}
/* now for the fun voodoo */
- overhead = META_OVERHEAD(fs);
+ overhead = calc_group_overhead(fs, groups-1, old_desc_blocks);
/*
* if this is the case then the last group is going to have data in it
@@ -2031,8 +2046,6 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
} else
overhead += 50;
- if (ext2fs_bg_has_super(fs, groups-1))
- overhead += SUPER_OVERHEAD(fs);
overhead += fs->super->s_first_data_block;
/*
--
1.7.12.rc0.22.gcdd159b
--
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