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    SubjectRe: [PATCH 15/41] whiteout: ext2 whiteout support
    On 2009-10-21, at 13:19, Valerie Aurora wrote:
    > This patch adds whiteout support to EXT2. A whiteout is an empty
    > directory
    > entry (inode == 0) with the file type set to EXT2_FT_WHT. Therefore it
    > allocates space in directories. Due to being implemented as a
    > filetype it is
    > necessary to have the EXT2_FEATURE_INCOMPAT_FILETYPE flag set.
    > diff --git a/include/linux/ext2_fs.h b/include/linux/ext2_fs.h
    > index 121720d..bd10826 100644
    > --- a/include/linux/ext2_fs.h
    > +++ b/include/linux/ext2_fs.h
    > @@ -189,6 +189,7 @@ struct ext2_group_desc
    > +#define EXT2_OPAQUE_FL 0x00040000

    Please check in the upstream e2fsprogs ext2_fs.h before defining new
    values for ext2/3/4. In this case, 0x40000 conflicts with
    which is of course bad.

    > @@ -503,10 +504,12 @@ struct ext2_super_block {
    > #define EXT2_FEATURE_INCOMPAT_META_BG 0x0010
    > +#define EXT2_FEATURE_INCOMPAT_WHITEOUT 0x0020

    This one doesn't conflict, probably due to luck, because 0x0040-0x0200
    already in use for other features. I'm not sure if 0x0020 was
    reserved for
    some other use, or just skipped to avoid potential conflicts.

    Cheers, Andreas
    Andreas Dilger
    Sr. Staff Engineer, Lustre Group
    Sun Microsystems of Canada, Inc.

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