btrfs: convert btrfs_buffered_write() to use folios

The buffered write path is still heavily utilizing the page interface.
Since we have converted it to do a page-by-page copying, it's much easier
to convert all involved functions to folio interface, this involves:

- btrfs_copy_from_user()
- btrfs_drop_folio()
- prepare_uptodate_page()
- prepare_one_page()
- lock_and_cleanup_extent_if_need()
- btrfs_dirty_page()

All function are changed to accept a folio parameter, and if the word
"page" is in the function name, change that to "folio" too.

The function btrfs_dirty_page() is exported for v1 space cache, convert
v1 cache call site to convert its page to folio for the new interface.

And there is a small enhancement for prepare_one_folio(), instead of
manually waiting for the page writeback, let __filemap_get_folio() to
handle that by using FGP_WRITEBEGIN, which implies
(FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE).

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/file.c

@@ -42,7 +42,7 @@
  * calls into generic code.
  */
 static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
-					 struct page *page, struct iov_iter *i)
+					 struct folio *folio, struct iov_iter *i)
 {
 	size_t copied = 0;
 	size_t total_copied = 0;
@@ -53,10 +53,10 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
 		/*
 		 * Copy data from userspace to the current page
 		 */
-		copied = copy_page_from_iter_atomic(page, offset, count, i);
+		copied = copy_folio_from_iter_atomic(folio, offset, count, i);
 
 		/* Flush processor's dcache for this page */
-		flush_dcache_page(page);
+		flush_dcache_folio(folio);
 
 		/*
 		 * if we get a partial write, we can end up with
@@ -68,7 +68,7 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
 		 * back to page at a time copies after we return 0.
 		 */
 		if (unlikely(copied < count)) {
-			if (!PageUptodate(page)) {
+			if (!folio_test_uptodate(folio)) {
 				iov_iter_revert(i, copied);
 				copied = 0;
 			}
@@ -84,45 +84,43 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
 }
 
 /*
- * unlocks pages after btrfs_file_write is done with them
+ * Unlock folio after btrfs_file_write() is done with it.
  */
-static void btrfs_drop_page(struct btrfs_fs_info *fs_info, struct page *page,
-			    u64 pos, u64 copied)
+static void btrfs_drop_folio(struct btrfs_fs_info *fs_info, struct folio *folio,
+			     u64 pos, u64 copied)
 {
 	u64 block_start = round_down(pos, fs_info->sectorsize);
 	u64 block_len = round_up(pos + copied, fs_info->sectorsize) - block_start;
 
 	ASSERT(block_len <= U32_MAX);
 	/*
-	 * Page checked is some magic around finding pages that have been
-	 * modified without going through btrfs_set_page_dirty clear it here.
+	 * Folio checked is some magic around finding folios that have been
+	 * modified without going through btrfs_dirty_folio().  Clear it here.
 	 * There should be no need to mark the pages accessed as
-	 * prepare_one_page() should have marked them accessed in
-	 * prepare_one_page() via find_or_create_page()
+	 * prepare_one_folio() should have marked them accessed in
+	 * prepare_one_folio() via find_or_create_page()
 	 */
-	btrfs_folio_clamp_clear_checked(fs_info, page_folio(page), block_start,
-					block_len);
-	unlock_page(page);
-	put_page(page);
+	btrfs_folio_clamp_clear_checked(fs_info, folio, block_start, block_len);
+	folio_unlock(folio);
+	folio_put(folio);
 }
 
 /*
  * After btrfs_copy_from_user(), update the following things for delalloc:
- * - Mark newly dirtied pages as DELALLOC in the io tree.
+ * - Mark newly dirtied folio as DELALLOC in the io tree.
  *   Used to advise which range is to be written back.
- * - Mark modified pages as Uptodate/Dirty and not needing COW fixup
+ * - Mark modified folio as Uptodate/Dirty and not needing COW fixup
  * - Update inode size for past EOF write
  */
-int btrfs_dirty_page(struct btrfs_inode *inode, struct page *page, loff_t pos,
-		     size_t write_bytes, struct extent_state **cached, bool noreserve)
+int btrfs_dirty_folio(struct btrfs_inode *inode, struct folio *folio, loff_t pos,
+		      size_t write_bytes, struct extent_state **cached, bool noreserve)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	int ret = 0;
 	u64 num_bytes;
 	u64 start_pos;
 	u64 end_of_last_block;
 	u64 end_pos = pos + write_bytes;
-	struct folio *folio = page_folio(page);
 	loff_t isize = i_size_read(&inode->vfs_inode);
 	unsigned int extra_bits = 0;
 
@@ -835,14 +833,12 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
 }
 
 /*
- * on error we return an unlocked page and the error value
- * on success we return a locked page and 0
+ * On error return an unlocked folio and the error value
+ * On success return a locked folio and 0
  */
-static int prepare_uptodate_page(struct inode *inode,
-				 struct page *page, u64 pos,
-				 u64 len, bool force_uptodate)
+static int prepare_uptodate_folio(struct inode *inode, struct folio *folio, u64 pos,
+				  u64 len, bool force_uptodate)
 {
-	struct folio *folio = page_folio(page);
 	u64 clamp_start = max_t(u64, pos, folio_pos(folio));
 	u64 clamp_end = min_t(u64, pos + len, folio_pos(folio) + folio_size(folio));
 	int ret = 0;
@@ -873,23 +869,13 @@ static int prepare_uptodate_page(struct inode *inode,
 	 * The private flag check is essential for subpage as we need to store
 	 * extra bitmap using folio private.
 	 */
-	if (page->mapping != inode->i_mapping || !folio_test_private(folio)) {
+	if (folio->mapping != inode->i_mapping || !folio_test_private(folio)) {
 		folio_unlock(folio);
 		return -EAGAIN;
 	}
 	return 0;
 }
 
-static fgf_t get_prepare_fgp_flags(bool nowait)
-{
-	fgf_t fgp_flags = FGP_LOCK | FGP_ACCESSED | FGP_CREAT;
-
-	if (nowait)
-		fgp_flags |= FGP_NOWAIT;
-
-	return fgp_flags;
-}
-
 static gfp_t get_prepare_gfp_flags(struct inode *inode, bool nowait)
 {
 	gfp_t gfp;
@@ -904,60 +890,60 @@ static gfp_t get_prepare_gfp_flags(struct inode *inode, bool nowait)
 }
 
 /*
- * this just gets page into the page cache and locks them down.
+ * Get folio into the page cache and lock it.
  */
-static noinline int prepare_one_page(struct inode *inode, struct page **page_ret,
-				     loff_t pos, size_t write_bytes,
-				     bool force_uptodate, bool nowait)
+static noinline int prepare_one_folio(struct inode *inode, struct folio **folio_ret,
+				      loff_t pos, size_t write_bytes,
+				      bool force_uptodate, bool nowait)
 {
 	unsigned long index = pos >> PAGE_SHIFT;
 	gfp_t mask = get_prepare_gfp_flags(inode, nowait);
-	fgf_t fgp_flags = get_prepare_fgp_flags(nowait);
-	struct page *page;
+	fgf_t fgp_flags = (nowait ? FGP_WRITEBEGIN | FGP_NOWAIT : FGP_WRITEBEGIN);
+	struct folio *folio;
 	int ret = 0;
 
 again:
-	page = pagecache_get_page(inode->i_mapping, index, fgp_flags,
-				  mask | __GFP_WRITE);
-	if (!page) {
+	folio = __filemap_get_folio(inode->i_mapping, index, fgp_flags, mask);
+	if (IS_ERR(folio)) {
 		if (nowait)
 			ret = -EAGAIN;
 		else
-			ret = -ENOMEM;
+			ret = PTR_ERR(folio);
 		return ret;
 	}
-	ret = set_page_extent_mapped(page);
+	/* Only support page sized folio yet. */
+	ASSERT(folio_order(folio) == 0);
+	ret = set_folio_extent_mapped(folio);
 	if (ret < 0) {
-		unlock_page(page);
-		put_page(page);
+		folio_unlock(folio);
+		folio_put(folio);
 		return ret;
 	}
-	ret = prepare_uptodate_page(inode, page, pos, write_bytes, force_uptodate);
+	ret = prepare_uptodate_folio(inode, folio, pos, write_bytes, force_uptodate);
 	if (ret) {
-		/* The page is already unlocked. */
-		put_page(page);
+		/* The folio is already unlocked. */
+		folio_put(folio);
 		if (!nowait && ret == -EAGAIN) {
 			ret = 0;
 			goto again;
 		}
 		return ret;
 	}
-	wait_on_page_writeback(page);
-	*page_ret = page;
+	*folio_ret = folio;
 	return 0;
 }
 
 /*
- * This function locks the extent and properly waits for data=ordered extents
- * to finish before allowing the pages to be modified if need.
+ * Locks the extent and properly waits for data=ordered extents to finish
+ * before allowing the folios to be modified if need.
  *
- * The return value:
+ * Return:
  * 1 - the extent is locked
  * 0 - the extent is not locked, and everything is OK
- * -EAGAIN - need re-prepare the pages
+ * -EAGAIN - need to prepare the folios again
  */
 static noinline int
-lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page *page,
+lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct folio *folio,
 				loff_t pos, size_t write_bytes,
 				u64 *lockstart, u64 *lockend, bool nowait,
 				struct extent_state **cached_state)
@@ -976,8 +962,8 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page *page,
 		if (nowait) {
 			if (!try_lock_extent(&inode->io_tree, start_pos, last_pos,
 					     cached_state)) {
-				unlock_page(page);
-				put_page(page);
+				folio_unlock(folio);
+				folio_put(folio);
 				return -EAGAIN;
 			}
 		} else {
@@ -991,8 +977,8 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page *page,
 		    ordered->file_offset <= last_pos) {
 			unlock_extent(&inode->io_tree, start_pos, last_pos,
 				      cached_state);
-			unlock_page(page);
-			put_page(page);
+			folio_unlock(folio);
+			folio_put(folio);
 			btrfs_start_ordered_extent(ordered);
 			btrfs_put_ordered_extent(ordered);
 			return -EAGAIN;
@@ -1006,10 +992,10 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page *page,
 	}
 
 	/*
-	 * We should be called after prepare_one_page() which should have locked
+	 * We should be called after prepare_one_folio() which should have locked
 	 * all pages in the range.
 	 */
-	WARN_ON(!PageLocked(page));
+	WARN_ON(!folio_test_locked(folio));
 
 	return ret;
 }
@@ -1190,12 +1176,12 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)
 		size_t copied;
 		size_t dirty_sectors;
 		size_t num_sectors;
-		struct page *page = NULL;
+		struct folio *folio = NULL;
 		int extents_locked;
 		bool force_page_uptodate = false;
 
 		/*
-		 * Fault pages before locking them in prepare_one_page()
+		 * Fault pages before locking them in prepare_one_folio()
 		 * to avoid recursive lock
 		 */
 		if (unlikely(fault_in_iov_iter_readable(i, write_bytes))) {
@@ -1261,16 +1247,16 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)
 			break;
 		}
 
-		ret = prepare_one_page(inode, &page, pos, write_bytes,
-				       force_page_uptodate, false);
+		ret = prepare_one_folio(inode, &folio, pos, write_bytes,
+					force_page_uptodate, false);
 		if (ret) {
 			btrfs_delalloc_release_extents(BTRFS_I(inode),
 						       reserve_bytes);
 			break;
 		}
 
 		extents_locked = lock_and_cleanup_extent_if_need(BTRFS_I(inode),
-						page, pos, write_bytes, &lockstart,
+						folio, pos, write_bytes, &lockstart,
 						&lockend, nowait, &cached_state);
 		if (extents_locked < 0) {
 			if (!nowait && extents_locked == -EAGAIN)
@@ -1282,7 +1268,7 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)
 			break;
 		}
 
-		copied = btrfs_copy_from_user(pos, write_bytes, page, i);
+		copied = btrfs_copy_from_user(pos, write_bytes, folio, i);
 
 		num_sectors = BTRFS_BYTES_TO_BLKS(fs_info, reserve_bytes);
 		dirty_sectors = round_up(copied + sector_offset,
@@ -1314,8 +1300,8 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)
 		release_bytes = round_up(copied + sector_offset,
 					fs_info->sectorsize);
 
-		ret = btrfs_dirty_page(BTRFS_I(inode), page, pos, copied,
-				       &cached_state, only_release_metadata);
+		ret = btrfs_dirty_folio(BTRFS_I(inode), folio, pos, copied,
+					&cached_state, only_release_metadata);
 
 		/*
 		 * If we have not locked the extent range, because the range's
@@ -1332,15 +1318,15 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)
 
 		btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes);
 		if (ret) {
-			btrfs_drop_page(fs_info, page, pos, copied);
+			btrfs_drop_folio(fs_info, folio, pos, copied);
 			break;
 		}
 
 		release_bytes = 0;
 		if (only_release_metadata)
 			btrfs_check_nocow_unlock(BTRFS_I(inode));
 
-		btrfs_drop_page(fs_info, page, pos, copied);
+		btrfs_drop_folio(fs_info, folio, pos, copied);
 
 		cond_resched();
 

fs/btrfs/file.h

@@ -34,8 +34,8 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
 ssize_t btrfs_do_write_iter(struct kiocb *iocb, struct iov_iter *from,
 			    const struct btrfs_ioctl_encoded_io_args *encoded);
 int btrfs_release_file(struct inode *inode, struct file *file);
-int btrfs_dirty_page(struct btrfs_inode *inode, struct page *page, loff_t pos,
-		     size_t write_bytes, struct extent_state **cached, bool noreserve);
+int btrfs_dirty_folio(struct btrfs_inode *inode, struct folio *folio, loff_t pos,
+		      size_t write_bytes, struct extent_state **cached, bool noreserve);
 int btrfs_fdatawrite_range(struct btrfs_inode *inode, loff_t start, loff_t end);
 int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos,
 			   size_t *write_bytes, bool nowait);

fs/btrfs/free-space-cache.c

@@ -1464,8 +1464,8 @@ static int __btrfs_write_out_cache(struct inode *inode,
 		u64 dirty_start = i * PAGE_SIZE;
 		u64 dirty_len = min_t(u64, dirty_start + PAGE_SIZE, i_size) - dirty_start;
 
-		ret = btrfs_dirty_page(BTRFS_I(inode), io_ctl->pages[i],
-				       dirty_start, dirty_len, &cached_state, false);
+		ret = btrfs_dirty_folio(BTRFS_I(inode), page_folio(io_ctl->pages[i]),
+					dirty_start, dirty_len, &cached_state, false);
 		if (ret < 0)
 			goto out_nospc;
 	}