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Re: [RFC PATCH 4/4] xfs: allow linkat() on O_TMPFILE files

To: Zhi Yong Wu <zwu.kernel@xxxxxxxxx>
Subject: Re: [RFC PATCH 4/4] xfs: allow linkat() on O_TMPFILE files
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 26 Nov 2013 08:46:11 +1100
Cc: xfs@xxxxxxxxxxx, Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1385379154-3802-5-git-send-email-zwu.kernel@xxxxxxxxx>
References: <1385379154-3802-1-git-send-email-zwu.kernel@xxxxxxxxx> <1385379154-3802-5-git-send-email-zwu.kernel@xxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Nov 25, 2013 at 07:32:34PM +0800, Zhi Yong Wu wrote:
> From: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
> 
> Enable O_TMPFILE support in linkat().
> 
> http://oss.sgi.com/archives/xfs/2013-08/msg00341.html
> 
> Signed-off-by: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
> ---
>  fs/xfs/xfs_inode.c      |   23 +++++++++++++++++++++--
>  fs/xfs/xfs_trans_resv.c |   13 +++++++++++++
>  fs/xfs/xfs_trans_resv.h |    2 ++
>  3 files changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index e1832de..7ab029b 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -62,6 +62,8 @@ kmem_zone_t *xfs_inode_zone;
>  
>  STATIC int xfs_iflush_int(xfs_inode_t *, xfs_buf_t *);
>  
> +STATIC int xfs_iunlink_remove(xfs_trans_t *, xfs_inode_t *);
> +
>  /*
>   * helper function to extract extent size hint from inode
>   */
> @@ -1119,7 +1121,9 @@ xfs_bumplink(
>  {
>       xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);
>  
> -     ASSERT(ip->i_d.di_nlink > 0);
> +     if ((VFS_I(ip)->i_nlink == 0) &&
> +         !(VFS_I(ip)->i_state & I_LINKABLE))
> +             ASSERT(ip->i_d.di_nlink > 0);
>       ip->i_d.di_nlink++;
>       inc_nlink(VFS_I(ip));
>       if ((ip->i_d.di_version == 1) &&
> @@ -1473,6 +1477,7 @@ xfs_link(
>  {
>       xfs_mount_t             *mp = tdp->i_mount;
>       xfs_trans_t             *tp;
> +     struct xfs_trans_res    *tres;
>       int                     error;
>       xfs_bmap_free_t         free_list;
>       xfs_fsblock_t           first_block;
> @@ -1498,7 +1503,14 @@ xfs_link(
>       tp = xfs_trans_alloc(mp, XFS_TRANS_LINK);
>       cancel_flags = XFS_TRANS_RELEASE_LOG_RES;
>       resblks = XFS_LINK_SPACE_RES(mp, target_name->len);
> -     error = xfs_trans_reserve(tp, &M_RES(mp)->tr_link, resblks, 0);
> +
> +     if ((VFS_I(sip)->i_nlink == 0) &&
> +         (VFS_I(sip)->i_state & I_LINKABLE))
> +             tres = &M_RES(mp)->tr_link_tmpfile;
> +     else
> +             tres = &M_RES(mp)->tr_link;
> +
> +     error = xfs_trans_reserve(tp, tres, resblks, 0);

Uggh. For the small amount of extra space needed for the unlinked
list reservation, I would simply add it to the tr_link reservation
and be done with it. That gets rid of the need for the noise here.

>       if (error == ENOSPC) {
>               resblks = 0;
>               error = xfs_trans_reserve(tp, &M_RES(mp)->tr_link, 0, 0);
> @@ -1530,6 +1542,13 @@ xfs_link(
>  
>       xfs_bmap_init(&free_list, &first_block);
>  
> +     if ((VFS_I(sip)->i_nlink == 0) &&
> +         (VFS_I(sip)->i_state & I_LINKABLE)) {
> +             error = xfs_iunlink_remove(tp, sip);
> +             if (error)
> +                     goto abort_return;
> +     }
> +
>       error = xfs_dir_createname(tp, tdp, target_name, sip->i_ino,
>                                       &first_block, &free_list, resblks);
>       if (error)
> diff --git a/fs/xfs/xfs_trans_resv.c b/fs/xfs/xfs_trans_resv.c
> index f1eebe4..7c1234e 100644
> --- a/fs/xfs/xfs_trans_resv.c
> +++ b/fs/xfs/xfs_trans_resv.c
> @@ -228,6 +228,15 @@ xfs_calc_link_reservation(
>                                     XFS_FSB_TO_B(mp, 1))));
>  }
>  
> +STATIC uint
> +xfs_calc_link_tmpfile_reservation(
> +     struct xfs_mount        *mp)
> +{
> +     return xfs_calc_link_reservation(mp) +
> +             xfs_calc_buf_res(2, XFS_FSB_TO_B(mp, 1)) +
> +             xfs_calc_buf_res(2, mp->m_sb.sb_sectsize);
> +}

As per above, fold this into xfs_calc_link_reservation() by adding a:


                + xfs_calc_iunlink_remove_resv(mp);

to the end of it.  Then you can also modify
xfs_calc_ifree_reservation() to use the same
xfs_calc_iunlink_remove_resv() function as well.

[ And similarly, looking back on the previous patch
xfs_calc_iunlink_add_resv can be used in xfs_calc_remove_reservation
so all the unlinked list manipulations are covered by the same
reservation calculations. ]

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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