On Mon, 20 Feb 2012, Phillip Susi wrote:
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> I was experimenting with e2fsck -E discard on image files and found
> some errors introduced by commit efa1a355. The following section of
> code attempts to discard unused portions of the inode table:
>
>
> /* 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);
> }
>
> There are two problems with this. The first is that trying to discard
> a count of zero blocks results in an -EINVAL, which silently halts (
> shouldn't this at least issue a warning? ) further discard attempts.
> The second I noticed after fixing that problem and had a bunch of
> valid inodes discarded. It looks like the intent of this code is to
> free the part of the inode table that lies beyond the highest used
> inode, but instead it is using the count of free inodes, so when you
> have some free inodes followed by some used inodes, the used inodes at
> the end get discarded.
>
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Oops, thanks for noticing. You're right with both problems you're
describing. I'll make a patch so that we discard only unused parts of
inode table.
Thanks again!
-Lukas
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