Re: [PATCH v8 03/12] memcg: add mem_cgroup_mark_inode_dirty()

[KAMEZAWA Hiroyuki]

On Fri,  3 Jun 2011 09:12:09 -0700
Greg Thelen <gthelen@xxxxxxxxxx> wrote:

> Create the mem_cgroup_mark_inode_dirty() routine, which is called when
> an inode is marked dirty.  In kernels without memcg, this is an inline
> no-op.
> 
> Add i_memcg field to struct address_space.  When an inode is marked
> dirty with mem_cgroup_mark_inode_dirty(), the css_id of current memcg is
> recorded in i_memcg.  Per-memcg writeback (introduced in a latter
> change) uses this field to isolate inodes associated with a particular
> memcg.
> 
> The type of i_memcg is an 'unsigned short' because it stores the css_id
> of the memcg.  Using a struct mem_cgroup pointer would be larger and
> also create a reference on the memcg which would hang memcg rmdir
> deletion.  Usage of a css_id is not a reference so cgroup deletion is
> not affected.  The memcg can be deleted without cleaning up the i_memcg
> field.  When a memcg is deleted its pages are recharged to the cgroup
> parent, and the related inode(s) are marked as shared thus
> disassociating the inodes from the deleted cgroup.
> 
> A mem_cgroup_mark_inode_dirty() tracepoint is also included to allow for
> easier understanding of memcg writeback operation.
> 
> Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

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