2013/10/11 Dave Chinner <david@xxxxxxxxxxxxx>:
> On Thu, Oct 10, 2013 at 04:00:13PM +0900, Namjae Jeon wrote:
>> >
>> > /*
>> > * Shift extent records to the left to cover a hole.
>> > *
>> > * The maximum number of extents to be shifted in a single operation
>> > * is @count, and @current_ext keeps track of the current extent
>> > * index we have shifted. If there is no hole to shift the extents
>> > * into, then we abort immediately.
>> > */
>> Thanks for your help. I will change this comment instead of original one.
>>
>> >> +int
>> >> +xfs_bmap_shift_extents(
>> >> + struct xfs_trans *tp,
>> >> + struct xfs_inode *ip,
>> >> + int *done,
>> >> + xfs_fileoff_t start_fsb,
>> >> + xfs_fileoff_t shift,
>> >
>> > Shift means ...? Number of extents to shift, a length, a number of
>> > block, or something else?
>> Ah, yes, shift_len would be a more proper name
>
> I'm not sure that's a lot better. What are we shifting? We are
> shifting the offset of the blocks, right? And the unit is in fsb?
> So perhaps offset_shift_fsb, and add that to the description of the
> function above?
Okay, I will change it as your suggestion.
>
>> >> + /*
>> >> + * Before shifting extent into hole, make sure that the hole
>> >> + * is large enough to accomodate the shift.
>> >> + */
>> >> + if (*current_ext) {
>> >> + state |= BMAP_LEFT_VALID;
>> >> + xfs_bmbt_get_all(xfs_iext_get_ext(ifp,
>> >> + *current_ext - 1), &left);
>> >> +
>> >> + if (isnullstartblock(left.br_startblock))
>> >> + state |= BMAP_LEFT_DELAY;
>> >> +
>> >> + if (startoff < left.br_startoff + left.br_blockcount)
>> >> + error = XFS_ERROR(EFSCORRUPTED);
>> >
>> > Why is the filesystem corrupted if the shift we asked for is too
>> > large for the hole in the file? I haven't seen any checks before
>> > this that guarantee that the hole is big enough for the shift...
>>
>> we call xfs_free_file_space to free enough blocks for shifting.
>> If still the space is not big enough will it be considered as fs corrupted?
>> What error could we return in this case?
>
> Hole punching rounds inwards, and the amount of rounding is not
> necessarily the nearest filesystem block. Again it's the block size
> smaller than page size case that will trip you over here, as the
> rounding when punching holes will be done to page size, not
> filesystem block size. Hence it's entirely possible that your
> calculated shift start and lengths don't match the size of the hole
> that was punched.
>
> That doesn't mean there was a corruption - just that the hole wasn't
> the size and shape that was expected....
Right. I will consider your points.
Thanks very much for your valuable comments.
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
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