linux-kernel - Re: [PATCH v3] ext4: fix hole punch failure when depth is greater than 0

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Message-ID: <CAOiN93mqfi4iLPa0VDTFkpr75duMj4owc8ys5JaAeyR2oztSjQ@mail.gmail.com>
Date:	Tue, 10 Jul 2012 10:05:28 +0530
From:	Ashish Sangwan <ashishsangwan2@...il.com>
To:	Ted Tso <tytso@....edu>
Cc:	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	lczerner@...hat.com, Ashish Sangwan <ashish.sangwan2@...il.com>,
	Namjae Jeon <linkinjeon@...il.com>
Subject: Re: [PATCH v3] ext4: fix hole punch failure when depth is greater
 than 0

Please ignore the last sent mail.
I will re-send the patch in new mail chain.

Thanks,
Ashish
On Tue, Jul 10, 2012 at 6:13 AM, Ashish Sangwan
<ashishsangwan2@...il.com> wrote:
> Whether to continue removing extents or not is decided by the return value
> of function ext4_ext_more_to_rm() which checks 2 conditions:
> a) if there are no more indexes to process.
> b) if the number of entries are decreased in the header of "depth -1".
>
> In case of hole punch, if the last block to be removed is not part of the
> last extent index than this index will not be deleted, hence the number of
> valid entries in the extent header of "depth - 1" will remain as it is and
> ext4_ext_more_to_rm will return 0 although the required blocks are not
> yet removed.
>
> This patch fixes the above mentioned problem as instead of removing the
> extents from the end of file, it starts removing the blocks from the
> particular extent from which removing blocks is actually required and
> continue backward until done.
>
> Signed-off-by: Ashish Sangwan <ashish.sangwan2@...il.com>
> Signed-off-by: Namjae Jeon <linkinjeon@...il.com>
> Reviewed-by: Lukas Czerner <lczerner@...hat.com>
> ---
>  fs/ext4/extents.c |   46 +++++++++++++++++++++++++++++-----------------
>  1 file changed, 29 insertions(+), 17 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 91341ec..45ac45d 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -2570,10 +2570,10 @@ static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,
>  {
>         struct super_block *sb = inode->i_sb;
>         int depth = ext_depth(inode);
> -       struct ext4_ext_path *path;
> +       struct ext4_ext_path *path = NULL;
>         ext4_fsblk_t partial_cluster = 0;
>         handle_t *handle;
> -       int i, err;
> +       int i = 0, err;
>
>         ext_debug("truncate since %u to %u\n", start, end);
>
> @@ -2606,8 +2606,12 @@ again:
>                 }
>                 depth = ext_depth(inode);
>                 ex = path[depth].p_ext;
> -               if (!ex)
> +               if (!ex) {
> +                       ext4_ext_drop_refs(path);
> +                       kfree(path);
> +                       path = NULL;
>                         goto cont;
> +               }
>
>                 ee_block = le32_to_cpu(ex->ee_block);
>
> @@ -2637,8 +2641,6 @@ again:
>                         if (err < 0)
>                                 goto out;
>                 }
> -               ext4_ext_drop_refs(path);
> -               kfree(path);
>         }
>  cont:
>
> @@ -2647,19 +2649,27 @@ cont:
>          * after i_size and walking into the tree depth-wise.
>          */
>         depth = ext_depth(inode);
> -       path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1), GFP_NOFS);
> -       if (path == NULL) {
> -               ext4_journal_stop(handle);
> -               return -ENOMEM;
> -       }
> -       path[0].p_depth = depth;
> -       path[0].p_hdr = ext_inode_hdr(inode);
> +       if (path) {
> +               int k = i = depth;
> +               while (--k > 0)
> +                       path[k].p_block =
> +                               le16_to_cpu(path[k].p_hdr->eh_entries)+1;
> +       } else {
> +               path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1),
> +                              GFP_NOFS);
> +               if (path == NULL) {
> +                       ext4_journal_stop(handle);
> +                       return -ENOMEM;
> +               }
> +               path[0].p_depth = depth;
> +               path[0].p_hdr = ext_inode_hdr(inode);
>
> -       if (ext4_ext_check(inode, path[0].p_hdr, depth)) {
> -               err = -EIO;
> -               goto out;
> +               if (ext4_ext_check(inode, path[0].p_hdr, depth)) {
> +                       err = -EIO;
> +                       goto out;
> +               }
>         }
> -       i = err = 0;
> +       err = 0;
>
>         while (i >= 0 && err == 0) {
>                 if (i == depth) {
> @@ -2773,8 +2783,10 @@ cont:
>  out:
>         ext4_ext_drop_refs(path);
>         kfree(path);
> -       if (err == -EAGAIN)
> +       if (err == -EAGAIN) {
> +               path = NULL
>                 goto again;
> +       }
>         ext4_journal_stop(handle);
>
>         return err;
> --
> 1.7.10.4
>
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