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Re: [Cluster-devel] [PATCH] gfs2: free disk inode which is deleted by remote node



Hi,

Don't worry about the wrong list, I did spot the patch anyway. I agree
with the principle of what you are trying to do, but something isn't
quite right. When I tried this on Friday I got a NULL pointer deref the
first time I tried to touch a file on the fs.

I think it needs a bit more work, but its certainly going in the right
direction,

Steve.

On Fri, 2009-08-14 at 23:05 +0800, Wengang Wang wrote:
> this patch is for the same problem that Benjamin Marzinski fixes at commit
> b94a170e96dc416828af9d350ae2e34b70ae7347
> 
> quotation of the original problem:
> 
> ---cut here---
> When a file is deleted from a gfs2 filesystem on one node, a dcache
> entry for it may still exist on other nodes in the cluster. If this
> happens, gfs2 will be unable to free this file on disk. Because of this,
> it's possible to have a gfs2 filesystem with no files on it and no free
> space. With this patch, when a node receives a callback notifying it
> that the file is being deleted on another node, it schedules a new
> workqueue thread to remove the file's dcache entry.
> ---end cut---
> 
> after applying Benjamin's patch, I think there is still a case in which the disk
> inode remains even when "no space" is hit. the case is that when running
> d_prune_aliases() against the inode, there are one or more dentries(aliases)
> which have reference count number > 0. in this case the dentries won't be pruned.
> and even later, the reference cound becomes to 0, the dentries can still be
> cached in memory. unfortunately, no callback come again, things come back to
> the state before the callback runs. thus the on disk inode remains there until
> in memory inode is removed for some other reason(shrinking inode cache or unmount
> the gfs2 volume..).
> 
> this patch is to remove those dentries when their reference count becomes to 0 and
> the inode is deleted by remote node. for implementation, gfs2_dentry_delete() is
> added as dentry_operations.d_delete. the function returns true when the inode is
> deleted by remote node. in dput(), gfs2_dentry_delete() is called and since it
> returns true, the dentry is unhashed from dcache and then removed. when all dentries
> are removed, the in memory inode get removed so that the on disk inode can be freed.
> 
> Signed-off-by: Wengang Wang <wen gang wang oracle com>
> ---
>  fs/gfs2/dentry.c |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
> index 022c66c..434f204 100644
> --- a/fs/gfs2/dentry.c
> +++ b/fs/gfs2/dentry.c
> @@ -107,8 +107,19 @@ static int gfs2_dhash(struct dentry *dentry, struct qstr *str)
>  	return 0;
>  }
>  
> +static int gfs2_dentry_delete(struct dentry *dentry)
> +{
> +	struct gfs2_inode *ginode = GFS2_I(dentry->d_inode);
> +
> +	if (test_bit(GLF_DEMOTE, &ginode->i_iopen_gh.gh_gl->gl_flags))
> +		return 1;
> +
> +	return 0;
> +}
> +
>  const struct dentry_operations gfs2_dops = {
>  	.d_revalidate = gfs2_drevalidate,
>  	.d_hash = gfs2_dhash,
> +	.d_delete = gfs2_dentry_delete,
>  };
>  


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