On Mon, Oct 10, 2016 at 03:38:04PM +0200, Christoph Hellwig wrote:
> Instead of doing a full extent list search for each extent that is to be
> deleted using xfs_bmapi_read and then doing another one inside of
> xfs_bunmapi_cow use the same scheme that xfs_bumapi uses: look up the
> last extent to be deleted and then use the extent index to walk downward
> until we are outside the range to be deleted.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/xfs_reflink.c | 114 ++++++++++++++++++++++-----------------------------
> fs/xfs/xfs_trace.h | 1 -
> 2 files changed, 49 insertions(+), 66 deletions(-)
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 08170bb..c4e7521 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -637,25 +637,22 @@ xfs_reflink_end_cow(
> xfs_off_t offset,
> xfs_off_t count)
> {
> - struct xfs_bmbt_irec irec;
> - struct xfs_bmbt_irec uirec;
> + struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
> + struct xfs_bmbt_irec got, prev, del;
> struct xfs_trans *tp;
> xfs_fileoff_t offset_fsb;
> xfs_fileoff_t end_fsb;
> - xfs_filblks_t count_fsb;
> xfs_fsblock_t firstfsb;
> struct xfs_defer_ops dfops;
> - int error;
> + int error, eof = 0;
> unsigned int resblks;
> - xfs_filblks_t ilen;
> xfs_filblks_t rlen;
> - int nimaps;
> + xfs_extnum_t idx;
>
> trace_xfs_reflink_end_cow(ip, offset, count);
>
> offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
> end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
> - count_fsb = (xfs_filblks_t)(end_fsb - offset_fsb);
>
> /* Start a rolling transaction to switch the mappings */
> resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);
> @@ -667,73 +664,61 @@ xfs_reflink_end_cow(
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> xfs_trans_ijoin(tp, ip, 0);
>
> - /* Go find the old extent in the CoW fork. */
> - while (offset_fsb < end_fsb) {
> - /* Read extent from the source file */
> - nimaps = 1;
> - count_fsb = (xfs_filblks_t)(end_fsb - offset_fsb);
> - error = xfs_bmapi_read(ip, offset_fsb, count_fsb, &irec,
> - &nimaps, XFS_BMAPI_COWFORK);
> - if (error)
> - goto out_cancel;
> - ASSERT(nimaps == 1);
> -
> - ASSERT(irec.br_startblock != DELAYSTARTBLOCK);
> - trace_xfs_reflink_cow_remap(ip, &irec);
> + xfs_bmap_search_extents(ip, end_fsb - 1, XFS_COW_FORK, &eof, &idx,
> + &got, &prev);
> + if (eof) {
> + ASSERT(idx > 0);
> + xfs_bmbt_get_all(xfs_iext_get_ext(ifp, --idx), &got);
> + }
Hmm, should this happen? Do we really want to proceed with the previous
extent?
I suppose the extent trim below would catch if we've dropped outside the
range of the I/O, but note that if trim extent sets blockcount = 0, it
doesn't necessarily reset the start offset for the (del.br_startoff ==
offset_fsb) check at next_extent. Perhaps that should break once the del
end offset precedes offset_fsb..?
Either way, it would be nice to have a comment here if there's some
reason we shouldn't just bail out or flag a problem...
>
> - /*
> - * We can have a hole in the CoW fork if part of a directio
> - * write is CoW but part of it isn't.
> - */
> - rlen = ilen = irec.br_blockcount;
> - if (irec.br_startblock == HOLESTARTBLOCK)
> + do {
> + ASSERT(!isnullstartblock(got.br_startblock));
> + del = got;
> + xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
> + if (!del.br_blockcount)
> goto next_extent;
>
> /* Unmap the old blocks in the data fork. */
> - while (rlen) {
> - xfs_defer_init(&dfops, &firstfsb);
> - error = __xfs_bunmapi(tp, ip, irec.br_startoff,
> - &rlen, 0, 1, &firstfsb, &dfops);
> - if (error)
> - goto out_defer;
> -
> - /*
> - * Trim the extent to whatever got unmapped.
> - * Remember, bunmapi works backwards.
> - */
> - uirec.br_startblock = irec.br_startblock + rlen;
> - uirec.br_startoff = irec.br_startoff + rlen;
> - uirec.br_blockcount = irec.br_blockcount - rlen;
> - irec.br_blockcount = rlen;
> - trace_xfs_reflink_cow_remap_piece(ip, &uirec);
> + xfs_defer_init(&dfops, &firstfsb);
> + rlen = del.br_blockcount;
> + error = __xfs_bunmapi(tp, ip, del.br_startoff, &rlen, 0, 1,
> + &firstfsb, &dfops);
> + if (error)
> + goto out_defer;
>
> - /* Free the CoW orphan record. */
> - error = xfs_refcount_free_cow_extent(tp->t_mountp,
> - &dfops, uirec.br_startblock,
> - uirec.br_blockcount);
> - if (error)
> - goto out_defer;
> + /* Trim the extent to whatever got unmapped. */
> + if (rlen) {
> + xfs_trim_extent(&del, del.br_startoff + rlen,
> + del.br_blockcount - rlen);
> + }
> + trace_xfs_reflink_cow_remap(ip, &del);
>
> - /* Map the new blocks into the data fork. */
> - error = xfs_bmap_map_extent(tp->t_mountp, &dfops,
> - ip, &uirec);
> - if (error)
> - goto out_defer;
> + /* Free the CoW orphan record. */
> + error = xfs_refcount_free_cow_extent(tp->t_mountp, &dfops,
> + del.br_startblock, del.br_blockcount);
> + if (error)
> + goto out_defer;
>
> - /* Remove the mapping from the CoW fork. */
> - error = xfs_bunmapi_cow(ip, &uirec);
> - if (error)
> - goto out_defer;
> + /* Map the new blocks into the data fork. */
> + error = xfs_bmap_map_extent(tp->t_mountp, &dfops, ip, &del);
> + if (error)
> + goto out_defer;
>
> - error = xfs_defer_finish(&tp, &dfops, ip);
> - if (error)
> - goto out_defer;
> - }
> + /* Remove the mapping from the CoW fork. */
> + xfs_bmap_del_extent_cow(ip, &idx, &got, &del);
> +
> + error = xfs_defer_finish(&tp, &dfops, ip);
> + if (error)
> + goto out_defer;
>
> next_extent:
> - /* Roll on... */
> - offset_fsb = irec.br_startoff + ilen;
> - }
> + if (del.br_startoff == offset_fsb || idx < 0)
> + break;
> +
> + xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), &got);
> + if (got.br_startoff >= del.br_startoff && --idx >= 0)
> + xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), &got);
> + } while (got.br_startoff < del.br_startoff);
Maybe it's just me, but I find this whole loop kind of confusing. I
realize it is tricky because we have to handle several different cases
with regard to index (no more extents to the left, bmap_del_extent_cow()
pushing index forward or back).
In staring at it a bit, I'm wondering if something like the following
would work:
/* walk backwards until we're out of the I/O range... */
while (got.br_startoff + got.br_blockcount > offset_fsb) {
del = got;
xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
/* extent delete may have bumped idx forward */
if (!del.br_blockcount) {
idx--;
goto next_extent;
}
...
next_extent:
if (idx < 0)
break;
xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), &got);
}
Thoughts?
Brian
>
> error = xfs_trans_commit(tp);
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> @@ -743,7 +728,6 @@ next_extent:
>
> out_defer:
> xfs_defer_cancel(&dfops);
> -out_cancel:
> xfs_trans_cancel(tp);
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> out:
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 520660d..f3b4418 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -3357,7 +3357,6 @@ DEFINE_INODE_IREC_EVENT(xfs_reflink_trim_irec);
> DEFINE_SIMPLE_IO_EVENT(xfs_reflink_cancel_cow_range);
> DEFINE_SIMPLE_IO_EVENT(xfs_reflink_end_cow);
> DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_remap);
> -DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_remap_piece);
>
> DEFINE_INODE_ERROR_EVENT(xfs_reflink_allocate_cow_range_error);
> DEFINE_INODE_ERROR_EVENT(xfs_reflink_cancel_cow_range_error);
> --
> 2.10.1.382.ga23ca1b
>
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