linux-ext4 - Re: [PATCH 5/8] ext4: call ext4_forget() from ext4_free

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Message-ID: <AANLkTimNATxwmz03ob6UoKzjqeKI6DLuA4FjYvmL9kbi@mail.gmail.com>
Date:	Sun, 27 Jun 2010 05:40:23 +0300
From:	"Amir G." <amir73il@...rs.sourceforge.net>
To:	Theodore Tso <tytso@....edu>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 5/8] ext4: call ext4_forget() from ext4_free_blocks()

Hi Ted,

There is a lurking bug that needs to be fixed in ext4_free_branches().
it can cause double freeing of blocks after crash.
please see bug description below.

Amir.

On Wed, Jun 23, 2010 at 10:01 PM, Amir G.
<amir73il@...rs.sourceforge.net> wrote:
> Hi,
>
> We have experienced bitmap inconsistencies after crash during file
> delete under heavy load.
> The crash is not file system related and I the following patch in
> ext4_free_branches() fixes the recovery problem.
>
> If the transaction is restarted and there is a crash before the new
> transaction is committed,
> then after recovery, the blocks that this indirect block points to
> have been freed, but the indirect block itself
> has not been freed and may still point to some of the free blocks
> (because of the ext4_forget()).
>
> So ext4_forget() should be called inside ext4_free_blocks() to avoid
> this problem.
> Are there any consequences to this patch that I am not aware of?
>
> Amir.
>
> Signed-off-by: Amir Goldstein <amir73il@...rs.sf.net>
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 42272d6..682e2fa 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4458,6 +4458,7 @@ static void ext4_free_branches(handle_t *handle,
> struct inode *inode,
>  {
>        ext4_fsblk_t nr;
>        __le32 *p;
> +       int     flags;
>
>        if (ext4_handle_is_aborted(handle))
>                return;
> @@ -4520,7 +4521,7 @@ static void ext4_free_branches(handle_t *handle,
> struct inode *inode,
>                         * revoke records must be emitted *before* clearing
>                         * this block's bit in the bitmaps.
>                         */
> -                       ext4_forget(handle, 1, inode, bh, bh->b_blocknr);
> +                       flags =
> EXT4_FREE_BLOCKS_METADATA|EXT4_FREE_BLOCKS_FORGET;
>
>                        /*
>                         * Everything below this this pointer has been
> @@ -4546,8 +4547,7 @@ static void ext4_free_branches(handle_t *handle,
> struct inode *inode,
>                                            blocks_for_truncate(inode));
>                        }
>
> -                       ext4_free_blocks(handle, inode, 0, nr, 1,
> -                                        EXT4_FREE_BLOCKS_METADATA);
> +                       ext4_free_blocks(handle, inode, 0, nr, 1, flags);
>
>                        if (parent_bh) {
>                                /*
>
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