[PATCH v4 06/18] f2fs: support atomic file large folios buffered write

[Nanzhe Zhao <nzzhao.sigma@gmail.com>]

From: Nanzhe Zhao <zhaonanzhe@xiaomi.com>

ioctl can convert an inode with large folio support into an atomic
file. Support large folio buffered writes for atomic files as well.

Add a large folio atomic write_begin helper that reserves COW mappings
for the write range. For partial head and tail subpages, read the
existing data from either the COW inode or the original inode before
marking the subpage uptodate.

Signed-off-by: Nanzhe Zhao <zhaonanzhe@xiaomi.com>
---
 fs/f2fs/data.c | 111 ++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 81 insertions(+), 30 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index f2b89181f..2ae3013b6 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -4245,18 +4245,16 @@ static int __reserve_data_block(struct inode *inode, pgoff_t index,
 }
 
 static int prepare_atomic_write_begin(struct f2fs_sb_info *sbi,
-			struct folio *folio, loff_t pos, unsigned int len,
+			struct inode *inode, pgoff_t index,
 			block_t *blk_addr, bool *node_changed)
 {
-	struct inode *inode = folio->mapping->host;
 	struct inode *cow_inode = F2FS_I(inode)->cow_inode;
-	pgoff_t index = folio->index;
 	int err = 0;
 	block_t ori_blk_addr = NULL_ADDR;
 	bool cow_has_reserved_block = false;
 
-	/* If pos is beyond the end of file, reserve a new block in COW inode */
-	if ((pos & PAGE_MASK) >= i_size_read(inode))
+	/* If index is beyond the end of file, reserve a new block in COW inode */
+	if (((loff_t)index << PAGE_SHIFT) >= i_size_read(inode))
 		goto reserve_block;
 
 	/* Look for the block in COW inode first */
@@ -4428,6 +4426,61 @@ static int prepare_large_folio_write_begin(struct inode *inode,
 	return 0;
 }
 
+static int prepare_large_folio_atomic_write_begin(struct inode *inode,
+		struct address_space *mapping, struct folio *folio, loff_t pos,
+		unsigned int len)
+{
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	size_t ori_off = offset_in_folio(folio, pos);
+	pgoff_t start, end, index;
+	int err = 0;
+
+	len = min_t(unsigned int, len, folio_size(folio) - ori_off);
+
+	if (!f2fs_ffs_find_or_alloc(folio))
+		return -ENOMEM;
+
+	/* Inline data must have been converted before reaching here. */
+	f2fs_bug_on(sbi, f2fs_has_inline_data(inode));
+
+	start = folio->index + (ori_off >> PAGE_SHIFT);
+	end = folio->index + ((ori_off + len - 1) >> PAGE_SHIFT);
+
+	for (index = start; index <= end; index++) {
+		block_t blkaddr = NULL_ADDR;
+		bool node_changed = false;
+		size_t off = (index - folio->index) << PAGE_SHIFT;
+
+		err = prepare_atomic_write_begin(sbi, inode, index,
+						&blkaddr, &node_changed);
+		if (err)
+			return err;
+
+		if (f2fs_ffs_test_blk_uptodate(folio, index))
+			goto balance;
+
+		if (blkaddr == NEW_ADDR) {
+			folio_zero_segment(folio, off, off + PAGE_SIZE);
+			f2fs_ffs_mark_subrange_uptodate(folio, off, PAGE_SIZE);
+			goto balance;
+		}
+
+		if (!f2fs_is_valid_blkaddr(sbi, blkaddr,
+					   DATA_GENERIC_ENHANCE_READ))
+			return -EFSCORRUPTED;
+
+		err = f2fs_submit_page_read_sync(inode, folio, index,
+						blkaddr);
+		if (err)
+			return err;
+balance:
+		if (f2fs_balance_fs_folio_locked(folio, mapping, node_changed))
+			return -EAGAIN;
+	}
+
+	return 0;
+}
+
 static int f2fs_write_begin(const struct kiocb *iocb,
 			    struct address_space *mapping,
 			    loff_t pos, unsigned len, struct folio **foliop,
@@ -4510,35 +4563,25 @@ static int f2fs_write_begin(const struct kiocb *iocb,
 	blen = min_t(unsigned int, len,
 		     folio_size(folio) - offset_in_folio(folio, pos));
 
-	if (f2fs_is_atomic_file(inode))
-		err = prepare_atomic_write_begin(sbi, folio, pos, len,
+	/*
+	 * Flush the cached IO of this folio and make sure it is stable
+	 * before touching it, especially for the large folio prepare
+	 * below which reads and updates subpage states.
+	 */
+	f2fs_folio_wait_writeback(folio, false, true);
+
+	if (f2fs_is_atomic_file(inode) && !folio_test_large(folio))
+		err = prepare_atomic_write_begin(sbi, inode, folio->index,
 					&blkaddr, &need_balance);
 	else if (!folio_test_large(folio))
 		err = prepare_write_begin(sbi, folio, pos, blen,
 					&blkaddr, &need_balance);
-	if (err)
-		goto put_folio;
-
-	if (need_balance && !IS_NOQUOTA(inode) &&
-			has_not_enough_free_secs(sbi, 0, 0)) {
-		folio_unlock(folio);
-		f2fs_balance_fs(sbi, true);
-		folio_lock(folio);
-		if (folio->mapping != mapping) {
-			/* The folio got truncated from under us */
-			folio_unlock(folio);
-			folio_put(folio);
-			goto repeat;
-		}
-	}
-
-	f2fs_folio_wait_writeback(folio, false, true);
-
-	if (folio_test_large(folio)) {
-		err = prepare_large_folio_write_begin(inode,
-					folio, pos, blen);
-		if (!err)
-			return 0;
+	else if (f2fs_is_atomic_file(inode))
+		err = prepare_large_folio_atomic_write_begin(inode,
+					mapping, folio, pos, len);
+	else
+		err = prepare_large_folio_write_begin(inode, folio, pos, blen);
+	if (err) {
 		if (err == -EAGAIN) {
 			f2fs_folio_put(folio, true);
 			goto repeat;
@@ -4546,6 +4589,14 @@ static int f2fs_write_begin(const struct kiocb *iocb,
 		goto put_folio;
 	}
 
+	if (f2fs_balance_fs_folio_locked(folio, mapping, need_balance)) {
+		f2fs_folio_put(folio, true);
+		goto repeat;
+	}
+
+	if (folio_test_large(folio))
+		return 0;
+
 	if (blen == folio_size(folio) || folio_test_uptodate(folio))
 		return 0;
 
-- 
2.43.0