On Thu, May 31, 2018 at 08:07:50PM +0200, Christoph Hellwig wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
...
>
> Signed-Off-By: Dave Chinner <dchinner@xxxxxxxxxx>
> [hch: forward port + slight refactoring]
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/xfs_aops.c | 96 ++++++++++++++++++++++-------------------------
> 1 file changed, 44 insertions(+), 52 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 6f57a785f4d3..a0ecfd63b858 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
...
> @@ -822,61 +830,46 @@ xfs_writepage_map(
> {
> LIST_HEAD(submit_list);
> struct xfs_ioend *ioend, *next;
> - struct buffer_head *bh, *head;
> + struct buffer_head *bh;
> ssize_t len = i_blocksize(inode);
> uint64_t file_offset; /* file offset of page */
> + unsigned poffset; /* offset into page */
> int error = 0;
> int count = 0;
> - unsigned int new_type;
>
> - bh = head = page_buffers(page);
> + /*
> + * Walk the blocks on the page, and we we run off then end of the
> + * current map or find the current map invalid, grab a new one.
> + * We only use bufferheads here to check per-block state - they no
> + * longer control the iteration through the page. This allows us to
> + * replace the bufferhead with some other state tracking mechanism in
> + * future.
> + */
> file_offset = page_offset(page);
> - do {
> + bh = page_buffers(page);
> + for (poffset = 0;
> + poffset < PAGE_SIZE;
> + poffset += len, file_offset += len, bh = bh->b_this_page) {
> + /* past the range we are writing, so nothing more to write. */
> if (file_offset >= end_offset)
> break;
>
> - /*
> - * set_page_dirty dirties all buffers in a page, independent
> - * of their state. The dirty state however is entirely
> - * meaningless for holes (!mapped && uptodate), so skip
> - * buffers covering holes here.
> - */
> - if (!buffer_mapped(bh) && buffer_uptodate(bh))
> - continue;
> -
> - if (buffer_unwritten(bh))
> - new_type = XFS_IO_UNWRITTEN;
> - else if (buffer_delay(bh))
> - new_type = XFS_IO_DELALLOC;
> - else if (buffer_uptodate(bh))
> - new_type = XFS_IO_OVERWRITE;
> - else {
> + if (!buffer_uptodate(bh)) {
> if (PageUptodate(page))
> ASSERT(buffer_mapped(bh));
> - /*
> - * This buffer is not uptodate and will not be
> - * written to disk.
> - */
> continue;
> }
>
> - /*
> - * If we already have a valid COW mapping keep using it.
> - */
> - if (wpc->io_type == XFS_IO_COW &&
> - xfs_imap_valid(inode, &wpc->imap, file_offset)) {
> - wpc->imap_valid = true;
> - new_type = XFS_IO_COW;
> - }
> -
> - if (wpc->io_type != new_type) {
> - wpc->io_type = new_type;
> - wpc->imap_valid = false;
> - }
> -
We drop the previously lifted check but unless I'm missing something wrt
my previous comments on the imap_valid && io_type == COW case, we still
have that unconditional allocation behavior. I suspect if the previous
patch updated the logic below (and preserved it moving forward while
also perhaps adding to the comment to explain why we must call
xfs_map_blocks() in certain cases for reflink inodes), that would fix up
both of these patches.
Otherwise the rest of the changes here look fine to me.
Brian
> if (wpc->imap_valid)
> wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap,
> file_offset);
> + /*
> + * If we don't have a valid map, now it's time to get a new one
> + * for this offset. This will convert delayed allocations
> + * (including COW ones) into real extents. If we return without
> + * a valid map, it means we landed in a hole and we skip the
> + * block.
> + */
> if (!wpc->imap_valid || xfs_is_reflink_inode(XFS_I(inode))) {
> error = xfs_map_blocks(wpc, inode, file_offset);
> if (error)
> @@ -889,11 +882,10 @@ xfs_writepage_map(
> continue;
>
> lock_buffer(bh);
> - if (wpc->io_type != XFS_IO_OVERWRITE)
> - xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
> + xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
> xfs_add_to_ioend(inode, bh, file_offset, wpc, wbc, &submit_list);
> count++;
> - } while (file_offset += len, ((bh = bh->b_this_page) != head));
> + }
>
> ASSERT(wpc->ioend || list_empty(&submit_list));
>
> --
> 2.17.0
>
> --
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