Re: [PATCH 1/3] Add extended attributes to ext2/3

[Andrew Morton <akpm@digeo.com>]

tytso@mit.edu wrote:
> 
> This is an updated submission of the extended attribute patches for
> ext2/3 (versus bk-current).  Many thanks to Cristoph, Andrea, and Andrew
> for their suggestions and cleanups.
> 
> This patch creates a meta block cache which is utilized by the ext3 and
> ext2 extended attribute patches (patches 2 and 3, respectively).  This
> cache allows directory blocks to be indexed by multiple keys.  In the
> case of the extended attribute patches, it is used to look up blocks by
> both the block number and by the hash of the extended attributes.  This
> is extremely important to allow the sharing of acl's when stored as
> extended attributes.  Otherwise every single file would require its own,
> separate, one block overhead to store then ACL, even though there might
> be a large number of files that have the same ACL.
> 

The key thing here appears to be the cache entry:

+struct mb_cache_entry {
+       struct list_head                e_lru_list;
+       struct mb_cache                 *e_cache;
+       atomic_t                        e_used;
+       dev_t                           e_dev;
+       unsigned long                   e_block;
+       struct list_head                e_block_list;
+       struct mb_cache_entry_index     e_indexes[0];
+};

This should be converted to use sector_t for >2TB support, and tested
with CONFIG_LBD=y and n.

The use of a dev_t search key is a bit old-fashioned.  Maybe
use the address of inode->i_sb->s_bdev?