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    SubjectRe: [PATCH] Set the initial TRIM information as TRIMMED
    On 12/1/11 1:00 AM, Kyungmin Park wrote:
    > From: Kyungmin Park <>
    > Now trim information doesn't stored at disk so every boot time. it's cleared.
    > and do the trim all disk groups.
    > But assume that it's already trimmed at previous time so don't need to trim it again. So set the intial state as trimmed.
    > Signed-off-by: Kyungmin Park <>
    > ---
    > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
    > index e2d8be8..97ef342 100644
    > --- a/fs/ext4/mballoc.c
    > +++ b/fs/ext4/mballoc.c
    > @@ -1098,6 +1098,12 @@ int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)
    > goto err;
    > }
    > mark_page_accessed(page);
    > +
    > + /*
    > + * TRIM information is not stored at disk so set the initial
    > + * state as trimmed. Since previous time it's already trimmed all
    > + */
    > + EXT4_MB_GRP_SET_TRIMMED(this_grp);

    Hm, so if there were freed but un-trimmed blocks at this point, we will
    never trim them until we free _another_ block in the group, right? That
    might be a reasonable tradeoff, but it is somewhat surprising behavior.

    i.e. say we do:

    mount /mnt
    rm -rf /mnt/very_big_file
    umount /mnt

    mount /mnt
    fitrim /mnt

    then we won't trim anything at all, right, despite there being many
    new free blocks? Which would be rather unexpected.

    If we don't store the trimmed state on disk, I think we should
    probably stick with the slower first-time trim, and the more obvious
    behavior (all free blocks are always trimmed whenever a trim
    command is issued).


    > err:
    > ext4_mb_put_buddy_page_lock(&e4b);
    > return ret;
    > --
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