Switch to using the iomap_page structure for checking sub-page uptodate
status and track sub-page I/O completion status, and remove large
quantities of boilerplate code working around buffer heads.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_aops.c  | 536 +++++++--------------------------------------
 fs/xfs/xfs_buf.h   |   1 -
 fs/xfs/xfs_iomap.c |   3 -
 fs/xfs/xfs_super.c |   2 +-
 fs/xfs/xfs_trace.h |  18 +-
 5 files changed, 79 insertions(+), 481 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index efa2cbb27d67..d279929e53fb 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c

@@ -768,7 +620,7 @@ xfs_aops_discard_page(
 	int			error;
 
 	if (XFS_FORCED_SHUTDOWN(mp))
-		goto out_invalidate;
+		goto out;
 
 	xfs_alert(mp,
 		"page discard on page "PTR_FMT", inode 0x%llx, offset %llu.",

@@ -778,15 +630,15 @@ xfs_aops_discard_page(
 			PAGE_SIZE / i_blocksize(inode));
 	if (error && !XFS_FORCED_SHUTDOWN(mp))
 		xfs_alert(mp, "page discard unable to remove delalloc mapping.");
-out_invalidate:
-	xfs_vm_invalidatepage(page, 0, PAGE_SIZE);
+out:
+	iomap_invalidatepage(page, 0, PAGE_SIZE);

 }
 
 /*
  * We implement an immediate ioend submission policy here to avoid needing to
  * chain multiple ioends and hence nest mempool allocations which can violate
  * forward progress guarantees we need to provide. The current ioend we are
- * adding buffers to is cached on the writepage context, and if the new buffer
+ * adding blocks to is cached on the writepage context, and if the new block
  * does not append to the cached ioend it will create a new ioend and cache that
  * instead.
  *

@@ -807,41 +659,28 @@ xfs_writepage_map(
 	uint64_t		end_offset)
 {
 	LIST_HEAD(submit_list);
+	struct iomap_page	*iop = to_iomap_page(page);
+	unsigned		len = i_blocksize(inode);
 	struct xfs_ioend	*ioend, *next;
-	struct buffer_head	*bh = NULL;
-	ssize_t			len = i_blocksize(inode);
-	int			error = 0;
-	int			count = 0;
-	loff_t			file_offset;	/* file offset of page */
-	unsigned		poffset;	/* offset into page */
+	int			error = 0, count = 0, i;
+	u64			file_offset;	/* file offset of page */
 
-	if (page_has_buffers(page))
-		bh = page_buffers(page);
+	ASSERT(iop || i_blocksize(inode) == PAGE_SIZE);
+	ASSERT(!iop || atomic_read(&iop->write_count) == 0);
 
 	/*
-	 * 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.
+	 * Walk through the page to find areas to write back. If we run off the
+	 * end of the current map or find the current map invalid, grab a new
+	 * one.
 	 */
-	for (poffset = 0, file_offset = page_offset(page);
-	     poffset < PAGE_SIZE;
-	     poffset += len, file_offset += len) {
-		/* past the range we are writing, so nothing more to write. */
-		if (file_offset >= end_offset)
-			break;
-
+	for (i = 0, file_offset = page_offset(page);
+	     i < (PAGE_SIZE >> inode->i_blkbits) && file_offset < end_offset;
+	     i++, file_offset += len) {
 		/*
 		 * Block does not contain valid data, skip it.
 		 */
-		if (bh && !buffer_uptodate(bh)) {
-			if (PageUptodate(page))
-				ASSERT(buffer_mapped(bh));
-			bh = bh->b_this_page;
+		if (iop && !test_bit(i, iop->uptodate))
 			continue;
-		}
 
 		/*
 		 * If we don't have a valid map, now it's time to get a new one

@@ -854,52 +693,33 @@ xfs_writepage_map(
 			error = xfs_map_blocks(inode, file_offset, &wpc->imap,
 					     &wpc->io_type);
 			if (error)
-				goto out;
+				break;
 		}
 
-		if (wpc->io_type == XFS_IO_HOLE) {
-			/*
-			 * 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 check we did
-			 * have a buffer covering a hole here and continue.
-			 */
-			if (bh)
-				bh = bh->b_this_page;
-			continue;
-		}
-
-		if (bh) {
-			xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
-			bh = bh->b_this_page;
+		if (wpc->io_type != XFS_IO_HOLE) {
+			xfs_add_to_ioend(inode, file_offset, page, iop, wpc,
+				wbc, &submit_list);
+			count++;
 		}
-		xfs_add_to_ioend(inode, file_offset, page, wpc, wbc,
-				&submit_list);
-		count++;
 	}
 
 	ASSERT(wpc->ioend || list_empty(&submit_list));
-
-out:
 	ASSERT(PageLocked(page));
 	ASSERT(!PageWriteback(page));
 
 	/*
-	 * On error, we have to fail the ioend here because we have locked
-	 * buffers in the ioend. If we don't do this, we'll deadlock
-	 * invalidating the page as that tries to lock the buffers on the page.
-	 * Also, because we may have set pages under writeback, we have to make
-	 * sure we run IO completion to mark the error state of the IO
-	 * appropriately, so we can't cancel the ioend directly here. That means
-	 * we have to mark this page as under writeback if we included any
-	 * buffers from it in the ioend chain so that completion treats it
-	 * correctly.
+	 * On error, we have to fail the ioend here because we may have set
+	 * pages under writeback, we have to make sure we run IO completion to
+	 * mark the error state of the IO appropriately, so we can't cancel the
+	 * ioend directly here.  That means we have to mark this page as under
+	 * writeback if we included any blocks from it in the ioend chain so
+	 * that completion treats it correctly.
 	 *
 	 * If we didn't include the page in the ioend, the on error we can
 	 * simply discard and unlock it as there are no other users of the page
-	 * or it's buffers right now. The caller will still need to trigger
-	 * submission of outstanding ioends on the writepage context so they are
-	 * treated correctly on error.
+	 * now.  The caller will still need to trigger submission of outstanding
+	 * ioends on the writepage context so they are treated correctly on
+	 * error.
 	 */
 	if (unlikely(error)) {
 		if (!count) {

@@ -940,8 +760,8 @@ xfs_writepage_map(
 	}
 
 	/*
-	 * We can end up here with no error and nothing to write if we race with
-	 * a partial page truncate on a sub-page block sized filesystem.
+	 * We can end up here with no error and nothing to write only if we race
+	 * with a partial page truncate on a sub-page block sized filesystem.
 	 */
 	if (!count)
 		end_page_writeback(page);

@@ -956,7 +776,6 @@ xfs_writepage_map(
  * For delalloc space on the page we need to allocate space and flush it.
  * For unwritten space on the page we need to start the conversion to
  * regular allocated space.
- * For any other dirty buffer heads on the page we should flush them.
  */
 STATIC int
 xfs_do_writepage(

@@ -1110,168 +929,6 @@ xfs_dax_writepages(
 			xfs_find_bdev_for_inode(mapping->host), wbc);
 }
 
-/*
- * Called to move a page into cleanable state - and from there
- * to be released. The page should already be clean. We always
- * have buffer heads in this call.
- *
- * Returns 1 if the page is ok to release, 0 otherwise.
- */
-STATIC int
-xfs_vm_releasepage(
-	struct page		*page,
-	gfp_t			gfp_mask)
-{
-	int			delalloc, unwritten;
-
-	trace_xfs_releasepage(page->mapping->host, page, 0, 0);
-
-	/*
-	 * mm accommodates an old ext3 case where clean pages might not have had
-	 * the dirty bit cleared. Thus, it can send actual dirty pages to
-	 * ->releasepage() via shrink_active_list(). Conversely,
-	 * block_invalidatepage() can send pages that are still marked dirty but
-	 * otherwise have invalidated buffers.
-	 *
-	 * We want to release the latter to avoid unnecessary buildup of the
-	 * LRU, so xfs_vm_invalidatepage() clears the page dirty flag on pages
-	 * that are entirely invalidated and need to be released.  Hence the
-	 * only time we should get dirty pages here is through
-	 * shrink_active_list() and so we can simply skip those now.
-	 *
-	 * warn if we've left any lingering delalloc/unwritten buffers on clean
-	 * or invalidated pages we are about to release.
-	 */
-	if (PageDirty(page))
-		return 0;
-
-	xfs_count_page_state(page, &delalloc, &unwritten);
-
-	if (WARN_ON_ONCE(delalloc))
-		return 0;
-	if (WARN_ON_ONCE(unwritten))
-		return 0;
-
-	return try_to_free_buffers(page);
-}
-
-/*
- * If this is O_DIRECT or the mpage code calling tell them how large the mapping
- * is, so that we can avoid repeated get_blocks calls.
- *
- * If the mapping spans EOF, then we have to break the mapping up as the mapping
- * for blocks beyond EOF must be marked new so that sub block regions can be
- * correctly zeroed. We can't do this for mappings within EOF unless the mapping
- * was just allocated or is unwritten, otherwise the callers would overwrite
- * existing data with zeros. Hence we have to split the mapping into a range up
- * to and including EOF, and a second mapping for beyond EOF.
- */
-static void
-xfs_map_trim_size(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	struct xfs_bmbt_irec	*imap,
-	xfs_off_t		offset,
-	ssize_t			size)
-{
-	xfs_off_t		mapping_size;
-
-	mapping_size = imap->br_startoff + imap->br_blockcount - iblock;
-	mapping_size <<= inode->i_blkbits;
-
-	ASSERT(mapping_size > 0);
-	if (mapping_size > size)
-		mapping_size = size;
-	if (offset < i_size_read(inode) &&
-	    (xfs_ufsize_t)offset + mapping_size >= i_size_read(inode)) {
-		/* limit mapping to block that spans EOF */
-		mapping_size = roundup_64(i_size_read(inode) - offset,
-					  i_blocksize(inode));
-	}
-	if (mapping_size > LONG_MAX)
-		mapping_size = LONG_MAX;
-
-	bh_result->b_size = mapping_size;
-}
-
-static int
-xfs_get_blocks(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	int			create)
-{
-	struct xfs_inode	*ip = XFS_I(inode);
-	struct xfs_mount	*mp = ip->i_mount;
-	xfs_fileoff_t		offset_fsb, end_fsb;
-	int			error = 0;
-	int			lockmode = 0;
-	struct xfs_bmbt_irec	imap;
-	int			nimaps = 1;
-	xfs_off_t		offset;
-	ssize_t			size;
-
-	BUG_ON(create);
-
-	if (XFS_FORCED_SHUTDOWN(mp))
-		return -EIO;
-
-	offset = (xfs_off_t)iblock << inode->i_blkbits;
-	ASSERT(bh_result->b_size >= i_blocksize(inode));
-	size = bh_result->b_size;
-
-	if (offset >= i_size_read(inode))
-		return 0;
-
-	/*
-	 * Direct I/O is usually done on preallocated files, so try getting
-	 * a block mapping without an exclusive lock first.
-	 */
-	lockmode = xfs_ilock_data_map_shared(ip);
-
-	ASSERT(offset <= mp->m_super->s_maxbytes);
-	if (offset > mp->m_super->s_maxbytes - size)
-		size = mp->m_super->s_maxbytes - offset;
-	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + size);
-	offset_fsb = XFS_B_TO_FSBT(mp, offset);
-
-	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
-			&nimaps, 0);
-	if (error)
-		goto out_unlock;
-	if (!nimaps) {
-		trace_xfs_get_blocks_notfound(ip, offset, size);
-		goto out_unlock;
-	}
-
-	trace_xfs_get_blocks_found(ip, offset, size,
-		imap.br_state == XFS_EXT_UNWRITTEN ?
-			XFS_IO_UNWRITTEN : XFS_IO_OVERWRITE, &imap);
-	xfs_iunlock(ip, lockmode);
-
-	/* trim mapping down to size requested */
-	xfs_map_trim_size(inode, iblock, bh_result, &imap, offset, size);
-
-	/*
-	 * For unwritten extents do not report a disk address in the buffered
-	 * read case (treat as if we're reading into a hole).
-	 */
-	if (xfs_bmap_is_real_extent(&imap))
-		xfs_map_buffer(inode, bh_result, &imap, offset);
-
-	/*
-	 * If this is a realtime file, data may be on a different device.
-	 * to that pointed to from the buffer_head b_bdev currently.
-	 */
-	bh_result->b_bdev = xfs_find_bdev_for_inode(inode);
-	return 0;
-
-out_unlock:
-	xfs_iunlock(ip, lockmode);
-	return error;
-}
-
 STATIC sector_t
 xfs_vm_bmap(
 	struct address_space	*mapping,

@@ -1301,9 +958,7 @@ xfs_vm_readpage(
 	struct page		*page)
 {
 	trace_xfs_vm_readpage(page->mapping->host, 1);
-	if (i_blocksize(page->mapping->host) == PAGE_SIZE)
-		return iomap_readpage(page, &xfs_iomap_ops);
-	return mpage_readpage(page, xfs_get_blocks);
+	return iomap_readpage(page, &xfs_iomap_ops);
 }
 
 STATIC int

@@ -1314,65 +969,26 @@ xfs_vm_readpages(
 	unsigned		nr_pages)
 {
 	trace_xfs_vm_readpages(mapping->host, nr_pages);
-	if (i_blocksize(mapping->host) == PAGE_SIZE)
-		return iomap_readpages(mapping, pages, nr_pages, &xfs_iomap_ops);
-	return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);
+	return iomap_readpages(mapping, pages, nr_pages, &xfs_iomap_ops);
 }
 
-/*
- * This is basically a copy of __set_page_dirty_buffers() with one
- * small tweak: buffers beyond EOF do not get marked dirty. If we mark them
- * dirty, we'll never be able to clean them because we don't write buffers
- * beyond EOF, and that means we can't invalidate pages that span EOF
- * that have been marked dirty. Further, the dirty state can leak into
- * the file interior if the file is extended, resulting in all sorts of
- * bad things happening as the state does not match the underlying data.
- *
- * XXX: this really indicates that bufferheads in XFS need to die. Warts like
- * this only exist because of bufferheads and how the generic code manages them.
- */
-STATIC int
-xfs_vm_set_page_dirty(
-	struct page		*page)
+static int
+xfs_vm_releasepage(
+	struct page		*page,
+	gfp_t			gfp_mask)
 {
-	struct address_space	*mapping = page->mapping;
-	struct inode		*inode = mapping->host;
-	loff_t			end_offset;
-	loff_t			offset;
-	int			newly_dirty;
-
-	if (unlikely(!mapping))
-		return !TestSetPageDirty(page);
-
-	end_offset = i_size_read(inode);
-	offset = page_offset(page);
-
-	spin_lock(&mapping->private_lock);
-	if (page_has_buffers(page)) {
-		struct buffer_head *head = page_buffers(page);
-		struct buffer_head *bh = head;
+	trace_xfs_releasepage(page->mapping->host, page, 0, 0);
+	return iomap_releasepage(page, gfp_mask);
+}
 
-		do {
-			if (offset < end_offset)
-				set_buffer_dirty(bh);
-			bh = bh->b_this_page;
-			offset += i_blocksize(inode);
-		} while (bh != head);
-	}
-	/*
-	 * Lock out page->mem_cgroup migration to keep PageDirty
-	 * synchronized with per-memcg dirty page counters.
-	 */
-	lock_page_memcg(page);
-	newly_dirty = !TestSetPageDirty(page);
-	spin_unlock(&mapping->private_lock);
-
-	if (newly_dirty)
-		__set_page_dirty(page, mapping, 1);
-	unlock_page_memcg(page);
-	if (newly_dirty)
-		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
-	return newly_dirty;
+static void
+xfs_vm_invalidatepage(
+	struct page		*page,
+	unsigned int		offset,
+	unsigned int		length)
+{
+	trace_xfs_invalidatepage(page->mapping->host, page, offset, length);
+	iomap_invalidatepage(page, offset, length);
 }
 
 static int

@@ -1390,13 +1006,13 @@ const struct address_space_operations xfs_address_space_operations = {
 	.readpages		= xfs_vm_readpages,
 	.writepage		= xfs_vm_writepage,
 	.writepages		= xfs_vm_writepages,
-	.set_page_dirty		= xfs_vm_set_page_dirty,
+	.set_page_dirty		= iomap_set_page_dirty,
 	.releasepage		= xfs_vm_releasepage,
 	.invalidatepage		= xfs_vm_invalidatepage,
 	.bmap			= xfs_vm_bmap,
 	.direct_IO		= noop_direct_IO,
-	.migratepage		= buffer_migrate_page,
-	.is_partially_uptodate  = block_is_partially_uptodate,
+	.migratepage		= iomap_migrate_page,
+	.is_partially_uptodate  = iomap_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 	.swap_activate		= xfs_iomap_swapfile_activate,
 };

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index f5f2b71c2fde..f3fa197bd272 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h

@@ -24,7 +24,6 @@
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/dax.h>
-#include <linux/buffer_head.h>
 #include <linux/uio.h>
 #include <linux/list_lru.h>
 

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 93c40da3378a..c646d84cd55e 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c

@@ -1031,9 +1031,6 @@ xfs_file_iomap_begin(
 	if (XFS_FORCED_SHUTDOWN(mp))
 		return -EIO;
 
-	if (i_blocksize(inode) < PAGE_SIZE)
-		iomap->flags |= IOMAP_F_BUFFER_HEAD;
-
 	if (((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == IOMAP_WRITE) &&
 			!IS_DAX(inode) && !xfs_get_extsz_hint(ip)) {
 		/* Reserve delalloc blocks for regular writeback. */

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 39e5ec3d407f..a9f23ec95216 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c

@@ -1866,7 +1866,7 @@ MODULE_ALIAS_FS("xfs");
 STATIC int __init
 xfs_init_zones(void)
 {
-	xfs_ioend_bioset = bioset_create(4 * MAX_BUF_PER_PAGE,
+	xfs_ioend_bioset = bioset_create(4 * (PAGE_SIZE / SECTOR_SIZE),
 			offsetof(struct xfs_ioend, io_inline_bio),
 			BIOSET_NEED_BVECS);
 	if (!xfs_ioend_bioset)

diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index ed8f774944ba..e4dc7c7f3da9 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h

@@ -1165,33 +1165,23 @@ DECLARE_EVENT_CLASS(xfs_page_class,
 		__field(loff_t, size)
 		__field(unsigned long, offset)
 		__field(unsigned int, length)
-		__field(int, delalloc)
-		__field(int, unwritten)
 	),
 	TP_fast_assign(
-		int delalloc = -1, unwritten = -1;
-
-		if (page_has_buffers(page))
-			xfs_count_page_state(page, &delalloc, &unwritten);
 		__entry->dev = inode->i_sb->s_dev;
 		__entry->ino = XFS_I(inode)->i_ino;
 		__entry->pgoff = page_offset(page);
 		__entry->size = i_size_read(inode);
 		__entry->offset = off;
 		__entry->length = len;
-		__entry->delalloc = delalloc;
-		__entry->unwritten = unwritten;
 	),
 	TP_printk("dev %d:%d ino 0x%llx pgoff 0x%lx size 0x%llx offset %lx "
-		  "length %x delalloc %d unwritten %d",
+		  "length %x",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		  __entry->ino,
 		  __entry->pgoff,
 		  __entry->size,
 		  __entry->offset,
-		  __entry->length,
-		  __entry->delalloc,
-		  __entry->unwritten)
+		  __entry->length)
 )
 
 #define DEFINE_PAGE_EVENT(name)		\

@@ -1275,9 +1265,6 @@ DEFINE_EVENT(xfs_imap_class, name,	\
 	TP_ARGS(ip, offset, count, type, irec))
 DEFINE_IOMAP_EVENT(xfs_map_blocks_found);
 DEFINE_IOMAP_EVENT(xfs_map_blocks_alloc);
-DEFINE_IOMAP_EVENT(xfs_get_blocks_found);
-DEFINE_IOMAP_EVENT(xfs_get_blocks_alloc);
-DEFINE_IOMAP_EVENT(xfs_get_blocks_map_direct);
 DEFINE_IOMAP_EVENT(xfs_iomap_alloc);
 DEFINE_IOMAP_EVENT(xfs_iomap_found);
 

@@ -1316,7 +1303,6 @@ DEFINE_EVENT(xfs_simple_io_class, name,	\
 	TP_ARGS(ip, offset, count))
 DEFINE_SIMPLE_IO_EVENT(xfs_delalloc_enospc);
 DEFINE_SIMPLE_IO_EVENT(xfs_unwritten_convert);
-DEFINE_SIMPLE_IO_EVENT(xfs_get_blocks_notfound);
 DEFINE_SIMPLE_IO_EVENT(xfs_setfilesize);
 DEFINE_SIMPLE_IO_EVENT(xfs_zero_eof);
 DEFINE_SIMPLE_IO_EVENT(xfs_end_io_direct_write);

-- 
2.17.0

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