Ted, thanks for going through this,
在 2008-08-01五的 01:49 -0400，Theodore Tso写道：
> ext4: Fix lack of credits BUG() when deleting a badly fragmented inode
>
> The extents codepath for ext4_truncate() requests journal transaction
> credits in very small chunks, requesting only what is needed. This
> means there may not be enough credits left on the transaction handle
> after ext4_truncate() returns and then when ext4_delete_inode() tries
> finish up its work, it may not have enough transaction credits,
> causing a BUG() oops in the jbd2 core.
But, ext4_delete_inode()'s transaction and ext4_truncate()'s transaction
are different, ext4_truncate() transaction is nested inside
ext4_delete_inode.
Inside ext4_delete_inode, the transaction is to log the changes in
ext4_orhan_del() and ext4_free_inode(). If I get right,
ext4_orhan_del() need credit to modify superblock and inode block,
ext4_free_inode() needs credit for modifying quota,xattr and inode
bitmap, group descriptor, superblock, and inode block.
Currently ext4_delete_inode() uses blocks_for_truncate(inode) to
calculate credits, by the time ext4_delete_inode() is called, i_blocks
seems to 0 (I need to double check this). So the credits is just
EXT4_DATA_TRANS_BLOCKS, which take care of the credits for inode,
superblock, xattr and quota, but missing is inode bitmap...I will double
check before I post a patch...
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index c7fb647..6d27e78 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -215,6 +215,18 @@ void ext4_delete_inode (struct inode * inode)
> inode->i_size = 0;
> if (inode->i_blocks)
> ext4_truncate(inode);
> +
> + /*
> + * ext4_ext_truncate() doesn't reserve any slop when it
> + * restarts journal transactions; therefore there may not be
> + * enough credits left in the handle to remove the inode from
> + * the orphan list and set the dtime field.
> + */
> + if (ext4_ext_journal_restart(handle, 3)) {
> + ext4_journal_stop(handle);
> + goto no_delete;
> + }
> +
> /*
> * Kill off the orphan record which ext4_truncate created.
> * AKPM: I think this can be inside the above `if'.
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