On Mon, 10 Sep 2018 00:02:41 -0700
Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> > + /*
> > + * if we don't find an overlapping extent, trim the range
> > we need to
> > + * allocate to fit the hole we found.
> > + */
>
> Please capitalize the first letter in each sentence.
>
> > + *shared = true;
> > + if (isnullstartblock(got.br_startblock)) {
> > + xfs_trim_extent(imap, got.br_startoff,
> > got.br_blockcount);
> > + return 0;
> > + }
>
> Taken out of the context of the bigger function this conditional
> could really use a comment as well.
>
> > + } while (tp);
>
> This looks a little odd as tp will always be true if we reach this
> point. I'd suggest to switch to a do { } while (1) or for (;;) style
> loop.
>
> Alternatively we could just skip the loop entirely now that we have
> the lookup + trim helper. Untested patch below:
I have just tested and it looks ok.
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 38f405415b88..79e2279d8e15 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -352,6 +352,47 @@ xfs_reflink_convert_cow(
> return error;
> }
>
> +/*
> + * Find the extent that maps the given range in the COW fork. Even
> if the extent
> + * is not shared we might have a preallocation for it in the COW
> fork. If so we
> + * use it that rather than trigger a new allocation.
> + */
> +static int
> +find_trim_cow_extent(
> + struct xfs_inode *ip,
> + struct xfs_bmbt_irec *imap,
> + bool *shared,
> + bool *found)
> +{
> + xfs_fileoff_t offset_fsb = imap->br_startoff;
> + xfs_filblks_t count_fsb = imap->br_blockcount;
> + struct xfs_iext_cursor icur;
> + struct xfs_bmbt_irec got;
> + bool trimmed;
> +
> + *found = false;
> +
> + /*
> + * If we don't find an overlapping extent, trim the range we
> need to
> + * allocate to fit the hole we found.
> + */
> + if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb,
> &icur, &got) ||
> + got.br_startoff > offset_fsb)
> + return xfs_reflink_trim_around_shared(ip, imap,
> shared, &trimmed); +
> + *shared = true;
> + if (isnullstartblock(got.br_startblock)) {
> + xfs_trim_extent(imap, got.br_startoff,
> got.br_blockcount);
> + return 0;
> + }
> +
> + /* real extent found - no need to allocate */
> + xfs_trim_extent(&got, offset_fsb, count_fsb);
> + *imap = got;
> + *found = true;
> + return 0;
> +}
> +
> /* Allocate all CoW reservations covering a range of blocks in a
> file. */ int
> xfs_reflink_allocate_cow(
> @@ -363,78 +404,62 @@ xfs_reflink_allocate_cow(
> struct xfs_mount *mp = ip->i_mount;
> xfs_fileoff_t offset_fsb = imap->br_startoff;
> xfs_filblks_t count_fsb = imap->br_blockcount;
> - struct xfs_bmbt_irec got;
> - struct xfs_trans *tp = NULL;
> + struct xfs_trans *tp;
> int nimaps, error = 0;
> - bool trimmed;
> + bool found;
> xfs_filblks_t resaligned;
> xfs_extlen_t resblks = 0;
> - struct xfs_iext_cursor icur;
>
> -retry:
> - ASSERT(xfs_is_reflink_inode(ip));
> ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
> + ASSERT(xfs_is_reflink_inode(ip));
>
> - /*
> - * Even if the extent is not shared we might have a
> preallocation for
> - * it in the COW fork. If so use it.
> - */
> - if (xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb,
> &icur, &got) &&
> - got.br_startoff <= offset_fsb) {
> - *shared = true;
> -
> - /* If we have a real allocation in the COW fork
> we're done. */
> - if (!isnullstartblock(got.br_startblock)) {
> - xfs_trim_extent(&got, offset_fsb, count_fsb);
> - *imap = got;
> - goto convert;
> - }
> + error = find_trim_cow_extent(ip, imap, shared, &found);
> + if (error || !*shared)
> + return error;
> + if (found)
> + goto convert;
>
> - xfs_trim_extent(imap, got.br_startoff,
> got.br_blockcount);
> - } else {
> - error = xfs_reflink_trim_around_shared(ip, imap,
> shared, &trimmed);
> - if (error || !*shared)
> - goto out;
> - }
> + resaligned = xfs_aligned_fsb_count(imap->br_startoff,
> + imap->br_blockcount, xfs_get_cowextsz_hint(ip));
> + resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
>
> - if (!tp) {
> - resaligned = xfs_aligned_fsb_count(imap->br_startoff,
> - imap->br_blockcount,
> xfs_get_cowextsz_hint(ip));
> - resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
> + xfs_iunlock(ip, *lockmode);
> + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks,
> 0, 0, &tp);
> + *lockmode = XFS_ILOCK_EXCL;
> + xfs_ilock(ip, *lockmode);
>
> - xfs_iunlock(ip, *lockmode);
> - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write,
> resblks, 0, 0, &tp);
> - *lockmode = XFS_ILOCK_EXCL;
> - xfs_ilock(ip, *lockmode);
> + if (error)
> + return error;
>
> - if (error)
> - return error;
> + error = xfs_qm_dqattach_locked(ip, false);
> + if (error)
> + goto out_trans_cancel;
>
> - error = xfs_qm_dqattach_locked(ip, false);
> - if (error)
> - goto out;
> - goto retry;
> + /* check for an overlapping extent again no that we dropped
> the ilock */
> + error = find_trim_cow_extent(ip, imap, shared, &found);
> + if (error || !*shared)
> + goto out_trans_cancel;
> + if (found) {
> + xfs_trans_cancel(tp);
> + goto convert;
> }
>
> error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0,
> XFS_QMOPT_RES_REGBLKS);
> if (error)
> - goto out;
> + goto out_trans_cancel;
>
> xfs_trans_ijoin(tp, ip, 0);
>
> - nimaps = 1;
> -
> /* Allocate the entire reservation as unwritten blocks. */
> + nimaps = 1;
> error = xfs_bmapi_write(tp, ip, imap->br_startoff,
> imap->br_blockcount, XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC,
> resblks, imap, &nimaps);
> if (error)
> - goto out_trans_cancel;
> + goto out_unreserve;
>
> xfs_inode_set_cowblocks_tag(ip);
> -
> - /* Finish up. */
> error = xfs_trans_commit(tp);
> if (error)
> return error;
> @@ -447,12 +472,12 @@ xfs_reflink_allocate_cow(
> return -ENOSPC;
> convert:
> return xfs_reflink_convert_cow_extent(ip, imap, offset_fsb,
> count_fsb); -out_trans_cancel:
> +
> +out_unreserve:
> xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,
> XFS_QMOPT_RES_REGBLKS);
> -out:
> - if (tp)
> - xfs_trans_cancel(tp);
> +out_trans_cancel:
> + xfs_trans_cancel(tp);
> return error;
> }
>
