[PATCH 3/5] xfs: xfs_cluster_write is redundant

Dave Chinner
2016-02-08T05:44:32Z

From: Dave Chinner <dchinner@redhat.com>

xfs_cluster_write() is not necessary now that xfs_vm_writepages()
aggregates writepage calls across a single mapping. This means we no
longer need to do page lookups in xfs_cluster_write, so writeback
only needs to look up th epage cache once per page being written.
This also removes a large amount of mostly duplicate code between
xfs_do_writepage() and xfs_convert_page().

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_aops.c | 215 ++----------------------------------------------------
1 file changed, 6 insertions(+), 209 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 4453d1d..e473f53 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -656,179 +656,6 @@ xfs_check_page_type(
return false;
}

-/*
- * Allocate & map buffers for page given the extent map. Write it out.
- * except for the original page of a writepage, this is called on
- * delalloc/unwritten pages only, for the original page it is possible
- * that the page has no mapping at all.
- */
-STATIC int
-xfs_convert_page(
- struct inode *inode,
- struct page *page,
- loff_t tindex,
- struct xfs_writepage_ctx *wpc,
- struct writeback_control *wbc)
-{
- struct buffer_head *bh, *head;
- xfs_off_t end_offset;
- unsigned long p_offset;
- int len, page_dirty;
- int count = 0, done = 0, uptodate = 1;
- xfs_off_t offset = page_offset(page);
-
- if (page->index != tindex)
- goto fail;
- if (!trylock_page(page))
- goto fail;
- if (PageWriteback(page))
- goto fail_unlock_page;
- if (page->mapping != inode->i_mapping)
- goto fail_unlock_page;
- if (!xfs_check_page_type(page, wpc->ioend->io_type, false))
- goto fail_unlock_page;
-
- /*
- * page_dirty is initially a count of buffers on the page before
- * EOF and is decremented as we move each into a cleanable state.
- *
- * Derivation:
- *
- * End offset is the highest offset that this page should represent.
- * If we are on the last page, (end_offset & (PAGE_CACHE_SIZE - 1))
- * will evaluate non-zero and be less than PAGE_CACHE_SIZE and
- * hence give us the correct page_dirty count. On any other page,
- * it will be zero and in that case we need page_dirty to be the
- * count of buffers on the page.
- */
- end_offset = min_t(unsigned long long,
- (xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT,
- i_size_read(inode));
-
- /*
- * If the current map does not span the entire page we are about to try
- * to write, then give up. The only way we can write a page that spans
- * multiple mappings in a single writeback iteration is via the
- * xfs_vm_writepage() function. Data integrity writeback requires the
- * entire page to be written in a single attempt, otherwise the part of
- * the page we don't write here doesn't get written as part of the data
- * integrity sync.
- *
- * For normal writeback, we also don't attempt to write partial pages
- * here as it simply means that write_cache_pages() will see it under
- * writeback and ignore the page until some point in the future, at
- * which time this will be the only page in the file that needs
- * writeback. Hence for more optimal IO patterns, we should always
- * avoid partial page writeback due to multiple mappings on a page here.
- */
- if (!xfs_imap_valid(inode, &wpc->imap, end_offset))
- goto fail_unlock_page;
-
- len = 1 << inode->i_blkbits;
- p_offset = min_t(unsigned long, end_offset & (PAGE_CACHE_SIZE - 1),
- PAGE_CACHE_SIZE);
- p_offset = p_offset ? roundup(p_offset, len) : PAGE_CACHE_SIZE;
- page_dirty = p_offset / len;
-
- /*
- * The moment we find a buffer that doesn't match our current type
- * specification or can't be written, abort the loop and start
- * writeback. As per the above xfs_imap_valid() check, only
- * xfs_vm_writepage() can handle partial page writeback fully - we are
- * limited here to the buffers that are contiguous with the current
- * ioend, and hence a buffer we can't write breaks that contiguity and
- * we have to defer the rest of the IO to xfs_vm_writepage().
- */
- bh = head = page_buffers(page);
- do {
- if (offset >= end_offset)
- break;
- if (!buffer_uptodate(bh))
- uptodate = 0;
- if (!(PageUptodate(page) || buffer_uptodate(bh))) {
- done = 1;
- break;
- }
-
- if (buffer_unwritten(bh) || buffer_delay(bh) ||
- buffer_mapped(bh)) {
- if (buffer_unwritten(bh))
- wpc->io_type = XFS_IO_UNWRITTEN;
- else if (buffer_delay(bh))
- wpc->io_type = XFS_IO_DELALLOC;
- else
- wpc->io_type = XFS_IO_OVERWRITE;
-
- /*
- * imap should always be valid because of the above
- * partial page end_offset check on the imap.
- */
- ASSERT(xfs_imap_valid(inode, &wpc->imap, offset));
-
- lock_buffer(bh);
- if (wpc->io_type != XFS_IO_OVERWRITE)
- xfs_map_at_offset(inode, bh, &wpc->imap, offset);
- xfs_add_to_ioend(inode, bh, offset, wpc);
-
- page_dirty--;
- count++;
- } else {
- done = 1;
- break;
- }
- } while (offset += len, (bh = bh->b_this_page) != head);
-
- if (uptodate && bh == head)
- SetPageUptodate(page);
-
- if (count) {
- if (--wbc->nr_to_write <= 0 &&
- wbc->sync_mode == WB_SYNC_NONE)
- done = 1;
- }
- xfs_start_page_writeback(page, !page_dirty, count);
-
- return done;
- fail_unlock_page:
- unlock_page(page);
- fail:
- return 1;
-}
-
-/*
- * Convert & write out a cluster of pages in the same extent as defined
- * by mp and following the start page.
- */
-STATIC void
-xfs_cluster_write(
- struct inode *inode,
- pgoff_t tindex,
- struct xfs_writepage_ctx *wpc,
- struct writeback_control *wbc,
- pgoff_t tlast)
-{
- struct pagevec pvec;
- int done = 0, i;
-
- pagevec_init(&pvec, 0);
- while (!done && tindex <= tlast) {
- unsigned len = min_t(pgoff_t, PAGEVEC_SIZE, tlast - tindex + 1);
-
- if (!pagevec_lookup(&pvec, inode->i_mapping, tindex, len))
- break;
-
- for (i = 0; i < pagevec_count(&pvec); i++) {
- done = xfs_convert_page(inode, pvec.pages[i], tindex++,
- wpc, wbc);
- if (done)
- break;
- }
-
- pagevec_release(&pvec);
- cond_resched();
- }
-}
-
STATIC void
xfs_vm_invalidatepage(
struct page *page,
@@ -945,7 +772,7 @@ xfs_do_writepage(
struct buffer_head *bh, *head;
loff_t offset;
__uint64_t end_offset;
- pgoff_t end_index, last_index;
+ pgoff_t end_index;
ssize_t len;
int err, uptodate = 1;
int count = 0;
@@ -975,12 +802,9 @@ xfs_do_writepage(
if (WARN_ON_ONCE(current->flags & PF_FSTRANS))
goto redirty;

- /* Is this page beyond the end of the file? */
- offset = i_size_read(inode);
- end_index = offset >> PAGE_CACHE_SHIFT;
- last_index = (offset - 1) >> PAGE_CACHE_SHIFT;
-
/*
+ * Is this page beyond the end of the file?
+ *
* The page index is less than the end_index, adjust the end_offset
* to the highest offset that this page should represent.
* -----------------------------------------------------
@@ -991,6 +815,8 @@ xfs_do_writepage(
* | desired writeback range | see else |
* ---------------------------------^------------------|
*/
+ offset = i_size_read(inode);
+ end_index = offset >> PAGE_CACHE_SHIFT;
if (page->index < end_index)
end_offset = (xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT;
else {
@@ -1120,36 +946,7 @@ xfs_do_writepage(
SetPageUptodate(page);

xfs_start_page_writeback(page, 1, count);
-
- /* if there is no IO to be submitted for this page, we are done */
- if (!count)
- return 0;
-
- ASSERT(wpc->iohead);
-
- /*
- * Any errors from this point onwards need tobe reported through the IO
- * completion path as we have marked the initial page as under writeback
- * and unlocked it.
- */
- if (wpc->imap_valid) {
- xfs_off_t end_index;
-
- end_index = wpc->imap.br_startoff + wpc->imap.br_blockcount;
-
- /* to bytes */
- end_index <<= inode->i_blkbits;
-
- /* to pages */
- end_index = (end_index - 1) >> PAGE_CACHE_SHIFT;
-
- /* check against file size */
- if (end_index > last_index)
- end_index = last_index;
-
- xfs_cluster_write(inode, page->index + 1, wpc, wbc, end_index);
- }
-
+ ASSERT(wpc->iohead || !count);
return 0;

error:
--
2.5.0