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Re: [PATCH v4 3/8] xfs: create helper to check whether to free eofblocks

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [PATCH v4 3/8] xfs: create helper to check whether to free eofblocks on inode
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 28 Sep 2012 16:59:17 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <1348767952-24229-4-git-send-email-bfoster@xxxxxxxxxx>
References: <1348767952-24229-1-git-send-email-bfoster@xxxxxxxxxx> <1348767952-24229-4-git-send-email-bfoster@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Sep 27, 2012 at 01:45:47PM -0400, Brian Foster wrote:
> This check is used in multiple places to determine whether we
> should check for (and potentially free) post EOF blocks on an
> inode. Add a helper to consolidate the check.
> 
> Note that when we remove an inode from the cache (xfs_inactive()),
> we are required to trim post-EOF blocks even if the inode is marked
> preallocated or append-only to maintain correct space accounting.
> The 'force' parameter to xfs_can_free_eofblocks() specifies whether
> we should ignore the prealloc/append-only status of the inode.
> 
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
....
> diff --git a/fs/xfs/xfs_vnodeops.h b/fs/xfs/xfs_vnodeops.h
> index 447e146..d5701e3 100644
> --- a/fs/xfs/xfs_vnodeops.h
> +++ b/fs/xfs/xfs_vnodeops.h
> @@ -1,6 +1,10 @@
>  #ifndef _XFS_VNODEOPS_H
>  #define _XFS_VNODEOPS_H 1
>  
> +#include "xfs_bmap_btree.h"
> +#include "xfs_dinode.h"
> +#include "xfs_inode.h"
> +
>  struct attrlist_cursor_kern;
>  struct file;
>  struct iattr;

Generally we try to avoid including XFS header files in XFS
header files, and instead order the header files in the .c files
appropriately.

> @@ -9,8 +13,42 @@ struct iovec;
>  struct kiocb;
>  struct pipe_inode_info;
>  struct uio;
> -struct xfs_inode;
>  
> +/*
> + * Test whether it is appropriate to check an inode for and free post EOF
> + * blocks. The 'force' parameter determines whether we should also consider
> + * regular files that are marked preallocated or append-only.
> + */
> +static inline bool
> +xfs_can_free_eofblocks(struct xfs_inode *ip, bool force)
> +{
> +     /* prealloc/delalloc exists only on regular files */
> +     if (!S_ISREG(ip->i_d.di_mode))
> +             return false;
> +
> +     /*
> +      * Zero sized files with no cached pages and delalloc blocks will not
> +      * have speculative prealloc/delalloc blocks to remove.
> +      */
> +     if (VFS_I(ip)->i_size == 0 &&
> +         VN_CACHED(VFS_I(ip)) == 0 &&
> +         ip->i_delayed_blks == 0)
> +             return false;
> +
> +     /* If we haven't read in the extent list, then don't do it now. */
> +     if (!(ip->i_df.if_flags & XFS_IFEXTENTS))
> +             return false;
> +
> +     /*
> +      * Do not free real preallocated or append-only files unless the file
> +      * has delalloc blocks and we are forced to remove them.
> +      */
> +     if (ip->i_d.di_flags & (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND))
> +             if (!force || ip->i_delayed_blks == 0)
> +                     return false;
> +
> +     return true;
> +}

And I'd say that function is too large for a static inline function
in a header file, so moving it to xfs_inode.c is probably
appropriate. I know, I asked you to write it like this, but
not looking at it for a couple weeks brings new persepctive ;)

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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