On Mon, Sep 09, 2019 at 08:27:21PM +0200, Christoph Hellwig wrote:
> Move more checks into the helpers that determine if we need a COW
> operation or allocation and split the return path for when an existing
> data for allocation has been found versus a new allocation.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_iomap.c | 74 ++++++++++++++++++++++++----------------------
> 1 file changed, 38 insertions(+), 36 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 0e575ca1e3fc..e4e79aa5b695 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -642,23 +642,42 @@ xfs_iomap_write_unwritten(
> static inline bool
> imap_needs_alloc(
> struct inode *inode,
> + unsigned flags,
> struct xfs_bmbt_irec *imap,
> int nimaps)
> {
> - return !nimaps ||
> - imap->br_startblock == HOLESTARTBLOCK ||
> - imap->br_startblock == DELAYSTARTBLOCK ||
> - (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);
> + /* don't allocate blocks when just zeroing */
> + if (flags & IOMAP_ZERO)
> + return false;
> + if (!nimaps ||
> + imap->br_startblock == HOLESTARTBLOCK ||
> + imap->br_startblock == DELAYSTARTBLOCK)
> + return true;
> + /* we convert unwritten extents before copying the data for DAX */
> + if (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN)
> + return true;
> + return false;
> }
>
> static inline bool
> -needs_cow_for_zeroing(
> +imap_needs_cow(
> + struct xfs_inode *ip,
> struct xfs_bmbt_irec *imap,
> + unsigned int flags,
> int nimaps)
> {
> - return nimaps &&
> - imap->br_startblock != HOLESTARTBLOCK &&
> - imap->br_state != XFS_EXT_UNWRITTEN;
> + if (!xfs_is_cow_inode(ip))
> + return false;
> +
> + /* when zeroing we don't have to COW holes or unwritten extents */
> + if (flags & IOMAP_ZERO) {
> + if (!nimaps ||
> + imap->br_startblock == HOLESTARTBLOCK ||
> + imap->br_state == XFS_EXT_UNWRITTEN)
> + return false;
> + }
> +
> + return true;
> }
>
> static int
> @@ -734,7 +753,6 @@ xfs_direct_write_iomap_begin(
> xfs_fileoff_t end_fsb = xfs_iomap_end_fsb(mp, offset, length);
> int nimaps = 1, error = 0;
> bool shared = false;
> - u16 iomap_flags = 0;
> unsigned lockmode;
>
> ASSERT(flags & (IOMAP_WRITE | IOMAP_ZERO));
> @@ -761,12 +779,7 @@ xfs_direct_write_iomap_begin(
> * Break shared extents if necessary. Checks for non-blocking IO have
> * been done up front, so we don't need to do them here.
> */
> - if (xfs_is_cow_inode(ip)) {
> - /* if zeroing doesn't need COW allocation, then we are done. */
> - if ((flags & IOMAP_ZERO) &&
> - !needs_cow_for_zeroing(&imap, nimaps))
> - goto out_found;
> -
> + if (imap_needs_cow(ip, &imap, flags, nimaps)) {
> /* may drop and re-acquire the ilock */
> error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,
> &lockmode, flags & IOMAP_DIRECT);
> @@ -778,18 +791,17 @@ xfs_direct_write_iomap_begin(
> length = XFS_FSB_TO_B(mp, end_fsb) - offset;
> }
>
> - /* Don't need to allocate over holes when doing zeroing operations. */
> - if (flags & IOMAP_ZERO)
> - goto out_found;
> + if (imap_needs_alloc(inode, flags, &imap, nimaps))
> + goto allocate_blocks;
>
> - if (!imap_needs_alloc(inode, &imap, nimaps))
> - goto out_found;
> + xfs_iunlock(ip, lockmode);
> + trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
> + return xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
>
> - /* If nowait is set bail since we are going to make allocations. */
> - if (flags & IOMAP_NOWAIT) {
> - error = -EAGAIN;
> +allocate_blocks:
> + error = -EAGAIN;
> + if (flags & IOMAP_NOWAIT)
> goto out_unlock;
> - }
>
> /*
> * We cap the maximum length we map to a sane size to keep the chunks
> @@ -808,22 +820,12 @@ xfs_direct_write_iomap_begin(
> */
> if (lockmode == XFS_ILOCK_EXCL)
> xfs_ilock_demote(ip, lockmode);
> - error = xfs_iomap_write_direct(ip, offset, length, &imap,
> - nimaps);
> + error = xfs_iomap_write_direct(ip, offset, length, &imap, nimaps);
> if (error)
> return error;
>
> - iomap_flags |= IOMAP_F_NEW;
> trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
> -
> -out_finish:
> - return xfs_bmbt_to_iomap(ip, iomap, &imap, iomap_flags);
> -
> -out_found:
> - ASSERT(nimaps);
> - xfs_iunlock(ip, lockmode);
> - trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
> - goto out_finish;
> + return xfs_bmbt_to_iomap(ip, iomap, &imap, IOMAP_F_NEW);
>
> out_found_cow:
> xfs_iunlock(ip, lockmode);
> --
> 2.20.1
>
