On Thu, Feb 02, 2017 at 04:55:23PM -0800, Darrick J. Wong wrote:
> On Wed, Feb 01, 2017 at 10:42:39PM +0100, Christoph Hellwig wrote:
> > Instead of preallocating all the required COW blocks in the high-level
> > write code do it inside the iomap code, like we do for all other I/O.
> >
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > ---
> > fs/xfs/xfs_file.c | 8 ---
> > fs/xfs/xfs_iomap.c | 31 +++++------
> > fs/xfs/xfs_reflink.c | 147 ++++++++++++++++++++-------------------------------
> > fs/xfs/xfs_reflink.h | 5 +-
> > fs/xfs/xfs_trace.h | 2 -
> > 5 files changed, 71 insertions(+), 122 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> > index 06236bf..56ac5b7 100644
> > --- a/fs/xfs/xfs_file.c
> > +++ b/fs/xfs/xfs_file.c
> > @@ -559,14 +559,6 @@ xfs_file_dio_aio_write(
> > }
> >
> > trace_xfs_file_direct_write(ip, count, iocb->ki_pos);
> > -
> > - /* If this is a block-aligned directio CoW, remap immediately. */
> > - if (xfs_is_reflink_inode(ip) && !unaligned_io) {
> > - ret = xfs_reflink_allocate_cow_range(ip, iocb->ki_pos, count);
> > - if (ret)
> > - goto out;
> > - }
> > -
> > ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, xfs_dio_write_end_io);
> > out:
> > xfs_iunlock(ip, iolock);
> > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> > index 9d811eb..de717e7 100644
> > --- a/fs/xfs/xfs_iomap.c
> > +++ b/fs/xfs/xfs_iomap.c
> > @@ -995,37 +995,31 @@ xfs_file_iomap_begin(
> > offset_fsb = XFS_B_TO_FSBT(mp, offset);
> > end_fsb = XFS_B_TO_FSB(mp, offset + length);
> >
> > - if (xfs_is_reflink_inode(ip) &&
> > - (flags & IOMAP_WRITE) && (flags & IOMAP_DIRECT)) {
> > - shared = xfs_reflink_find_cow_mapping(ip, offset, &imap);
> > - if (shared) {
> > - xfs_iunlock(ip, lockmode);
> > - goto alloc_done;
> > - }
> > - ASSERT(!isnullstartblock(imap.br_startblock));
> > - }
> > -
> > error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
> > &nimaps, 0);
> > if (error)
> > goto out_unlock;
> >
> > - if ((flags & IOMAP_REPORT) ||
> > - (xfs_is_reflink_inode(ip) &&
> > - (flags & IOMAP_WRITE) && (flags & IOMAP_DIRECT))) {
> > + if (flags & IOMAP_REPORT) {
> > /* Trim the mapping to the nearest shared extent boundary. */
> > error = xfs_reflink_trim_around_shared(ip, &imap, &shared,
> > &trimmed);
> > if (error)
> > goto out_unlock;
> > -
> > - ASSERT((flags & IOMAP_REPORT) || !shared);
> > }
> >
> > if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {
> > - error = xfs_reflink_reserve_cow(ip, &imap, &shared);
> > - if (error)
> > - goto out_unlock;
> > + if (flags & IOMAP_DIRECT) {
> > + /* may drop and re-acquire the ilock */
> > + error = xfs_reflink_allocate_cow(ip, offset_fsb, end_fsb,
> > + &imap, &shared, &lockmode);
> > + if (error)
> > + goto out_unlock;
> > + } else {
> > + error = xfs_reflink_reserve_cow(ip, &imap, &shared);
> > + if (error)
> > + goto out_unlock;
> > + }
> >
> > end_fsb = imap.br_startoff + imap.br_blockcount;
> > length = XFS_FSB_TO_B(mp, end_fsb) - offset;
> > @@ -1054,7 +1048,6 @@ xfs_file_iomap_begin(
> > if (error)
> > return error;
> >
> > -alloc_done:
> > iomap->flags = IOMAP_F_NEW;
> > trace_xfs_iomap_alloc(ip, offset, length, 0, &imap);
> > } else {
> > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> > index 1a96741..d5a2cf2 100644
> > --- a/fs/xfs/xfs_reflink.c
> > +++ b/fs/xfs/xfs_reflink.c
> > @@ -384,74 +384,84 @@ xfs_reflink_convert_cow(
> > }
> >
> > /* Allocate all CoW reservations covering a range of blocks in a file. */
> > -static int
> > -__xfs_reflink_allocate_cow(
> > +int
> > +xfs_reflink_allocate_cow(
> > struct xfs_inode *ip,
> > - xfs_fileoff_t *offset_fsb,
> > - xfs_fileoff_t end_fsb)
> > + xfs_fileoff_t offset_fsb,
> > + xfs_fileoff_t end_fsb,
> > + struct xfs_bmbt_irec *imap,
> > + bool *shared,
> > + uint *lockmode)
> > {
> > struct xfs_mount *mp = ip->i_mount;
> > - struct xfs_bmbt_irec imap, got;
> > + struct xfs_bmbt_irec got;
> > struct xfs_defer_ops dfops;
> > - struct xfs_trans *tp;
> > + struct xfs_trans *tp = NULL;
> > xfs_fsblock_t first_block;
> > - int nimaps, error, lockmode;
> > - bool shared, trimmed;
> > + int nimaps, error = 0;
> > + bool trimmed;
> > xfs_filblks_t resaligned;
> > - xfs_extlen_t resblks;
> > + xfs_extlen_t resblks = 0;
> > xfs_extnum_t idx;
> >
> > - resaligned = xfs_aligned_fsb_count(*offset_fsb, end_fsb - *offset_fsb,
> > - xfs_get_cowextsz_hint(ip));
> > - resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
> > -
> > - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
> > - if (error)
> > - return error;
> > -
> > - lockmode = XFS_ILOCK_EXCL;
> > - xfs_ilock(ip, lockmode);
> > +retry:
> > + ASSERT(xfs_is_reflink_inode(ip));
> > + ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
> >
> > /*
> > * 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, &idx, &got) &&
> > - got.br_startoff <= *offset_fsb) {
> > + if (xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &idx, &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,
> > - end_fsb - *offset_fsb);
> > - *offset_fsb = got.br_startoff + got.br_blockcount;
> > - goto out_trans_cancel;
> > + xfs_trim_extent(&got, offset_fsb, end_fsb - offset_fsb);
> > + *imap = got;
> > + goto out;
> > }
> > +
> > + xfs_trim_extent(imap, got.br_startoff, got.br_blockcount);
> > } else {
> > - nimaps = 1;
> > - error = xfs_bmapi_read(ip, *offset_fsb, end_fsb - *offset_fsb,
> > - &imap, &nimaps, 0);
> > + error = xfs_reflink_trim_around_shared(ip, imap, shared, &trimmed);
> > + if (error || !*shared)
> > + goto out;
> > + }
> > +
> > + if (!tp) {
> > + resaligned = xfs_aligned_fsb_count(offset_fsb,
> > + end_fsb - offset_fsb, 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);
> > +
> > if (error)
> > - goto out_trans_cancel;
> > - ASSERT(nimaps == 1);
> > + return error;
> >
> > - /* Trim the mapping to the nearest shared extent boundary. */
> > - error = xfs_reflink_trim_around_shared(ip, &imap, &shared,
> > - &trimmed);
> > + error = xfs_qm_dqattach_locked(ip, 0);
> > if (error)
> > - goto out_trans_cancel;
> > + goto out;
> >
> > - if (!shared) {
> > - *offset_fsb = imap.br_startoff + imap.br_blockcount;
> > - goto out_trans_cancel;
> > - }
> > + /* Read extent from the source file. */
> > + nimaps = 1;
> > + error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
> > + imap, &nimaps, 0);
> > + if (error)
> > + goto out;
> > + ASSERT(nimaps == 1);
> >
> > - *offset_fsb = imap.br_startoff;
> > - end_fsb = imap.br_startoff + imap.br_blockcount;
> > + goto retry;
> > }
> >
> > error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0,
> > XFS_QMOPT_RES_REGBLKS);
> > if (error)
> > - goto out_trans_cancel;
> > + goto out;
> >
> > xfs_trans_ijoin(tp, ip, 0);
> >
> > @@ -459,9 +469,9 @@ __xfs_reflink_allocate_cow(
> > nimaps = 1;
> >
> > /* Allocate the entire reservation as unwritten blocks. */
> > - error = xfs_bmapi_write(tp, ip, *offset_fsb, end_fsb - *offset_fsb,
> > + error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
> > XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, &first_block,
> > - resblks, &imap, &nimaps, &dfops);
> > + resblks, imap, &nimaps, &dfops);
> > if (error)
> > goto out_bmap_cancel;
> >
> > @@ -470,60 +480,15 @@ __xfs_reflink_allocate_cow(
> > if (error)
> > goto out_bmap_cancel;
> >
> > - error = xfs_trans_commit(tp);
> > - if (error)
> > - goto out_unlock;
> > -
> > - *offset_fsb = imap.br_startoff + imap.br_blockcount;
> > -
> > -out_unlock:
> > - xfs_iunlock(ip, lockmode);
> > - return error;
> > + return xfs_trans_commit(tp);
> >
> > out_bmap_cancel:
> > xfs_defer_cancel(&dfops);
> > xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,
> > XFS_QMOPT_RES_REGBLKS);
> > -out_trans_cancel:
> > - xfs_trans_cancel(tp);
> > - goto out_unlock;
> > -}
> > -
> > -/* Allocate all CoW reservations covering a part of a file. */
> > -int
> > -xfs_reflink_allocate_cow_range(
> > - struct xfs_inode *ip,
> > - xfs_off_t offset,
> > - xfs_off_t count)
> > -{
> > - struct xfs_mount *mp = ip->i_mount;
> > - xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
> > - xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
> > - int error;
> > -
> > - ASSERT(xfs_is_reflink_inode(ip));
> > -
> > - trace_xfs_reflink_allocate_cow_range(ip, offset, count);
> > -
> > - /*
> > - * Make sure that the dquots are there.
> > - */
> > - error = xfs_qm_dqattach(ip, 0);
> > - if (error)
> > - return error;
> > -
> > - while (offset_fsb < end_fsb) {
> > - error = __xfs_reflink_allocate_cow(ip, &offset_fsb, end_fsb);
> > - if (error) {
> > - trace_xfs_reflink_allocate_cow_range_error(ip, error,
> > - _RET_IP_);
> > - goto out;
> > - }
> > - }
> > -
> > - /* Convert the CoW extents to regular. */
> > - error = xfs_reflink_convert_cow(ip, offset, count);
>
> I think this is incorrect -- we create an unwritten extent in the cow
> fork above (BMAP_COWFORK | BMAP_PREALLOC) but we no longer convert the
> part we're actually writing to a real extent. This means that
> _reflink_cow won't actually remap anything that we've written.
It's not correct and I messed up when rebasing - the version I tested
still had it and worked. Sigh..
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