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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
    flag
    values for ext2/3/4. In this case, 0x40000 conflicts with
    EXT4_HUGE_FILE_FL,
    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
    are
    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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