[PATCH 15/20] f2fs: support subpage blocks in atomic writes

[Daeho Jeong <daeho43@gmail.com>]

From: Daeho Jeong <daehojeong@google.com>

Writeback already writes dirty blocks to the COW inode per block. Make
write_begin of atomic files reserve and read COW blocks per block as
well, and remove the -EOPNOTSUPP checks. Skipping the read of the
blocks that a write fully covers also applies to large folios when the
block size equals PAGE_SIZE.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
---
 fs/f2fs/data.c | 24 ++++++++++++++++--------
 fs/f2fs/file.c |  5 +----
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index a23fd4b01a4c..4e4d1b0d6004 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -4624,7 +4624,7 @@ static int f2fs_write_cache_folios(struct address_space *mapping,
 		}
 
 		if (f2fs_has_subpage_blocks(sbi) &&
-		    (f2fs_compressed_file(inode) || f2fs_is_atomic_file(inode))) {
+		    f2fs_compressed_file(inode)) {
 			WARN_ON_ONCE(1);
 			mapping_set_error(mapping, -EOPNOTSUPP);
 			folio_clear_dirty_for_io(folio);
@@ -5247,7 +5247,7 @@ static int prepare_large_folio_write_begin(struct inode *inode,
 	int err = 0;
 
 	if (f2fs_has_subpage_blocks(sbi) &&
-	    (f2fs_compressed_file(inode) || f2fs_is_atomic_file(inode)))
+	    f2fs_compressed_file(inode))
 		return -EOPNOTSUPP;
 
 	/*
@@ -5359,13 +5359,16 @@ static int prepare_large_folio_atomic_write_begin(struct inode *inode,
 	/* 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);
+	start = f2fs_folio_lblk(sbi, folio) + (ori_off >> sbi->log_blocksize);
+	end = f2fs_folio_lblk(sbi, folio) +
+		((ori_off + len - 1) >> sbi->log_blocksize);
 
 	for (index = start; index <= end; index++) {
+		loff_t block_start = F2FS_BLK_TO_BYTES(sbi, index);
+		loff_t block_end = block_start + F2FS_BLKSIZE(sbi);
 		block_t blkaddr = NULL_ADDR;
 		bool node_changed = false;
-		size_t off = (index - folio->index) << PAGE_SHIFT;
+		size_t off = f2fs_folio_byte_offset(sbi, folio, index);
 
 		err = prepare_atomic_write_begin(sbi, inode, index,
 						&blkaddr, &node_changed,
@@ -5373,12 +5376,17 @@ static int prepare_large_folio_atomic_write_begin(struct inode *inode,
 		if (err)
 			return err;
 
+		/* Skip read if the write covers the entire block. */
+		if (pos <= block_start && pos + len >= block_end)
+			goto balance;
+
 		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);
+			folio_zero_segment(folio, off, off + F2FS_BLKSIZE(sbi));
+			f2fs_ffs_mark_subrange_uptodate(folio, off,
+							F2FS_BLKSIZE(sbi));
 			goto balance;
 		}
 
@@ -5436,7 +5444,7 @@ static int f2fs_write_begin(const struct kiocb *iocb,
 	}
 
 	if (f2fs_has_subpage_blocks(sbi) &&
-	    (f2fs_compressed_file(inode) || f2fs_is_atomic_file(inode))) {
+	    f2fs_compressed_file(inode)) {
 		err = -EOPNOTSUPP;
 		goto fail;
 	}
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 1c440b5fa9bd..91f792cf879f 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2299,7 +2299,7 @@ static long f2fs_fallocate(struct file *file, int mode,
 	}
 
 	if (f2fs_has_subpage_blocks(F2FS_I_SB(inode))) {
-		if (f2fs_is_atomic_file(inode) || f2fs_compressed_file(inode)) {
+		if (f2fs_compressed_file(inode)) {
 			ret = -EOPNOTSUPP;
 			goto out;
 		}
@@ -2553,9 +2553,6 @@ static int f2fs_ioc_start_atomic_write(struct file *filp, bool truncate)
 	loff_t isize;
 	int ret;
 
-	if (f2fs_has_subpage_blocks(sbi))
-		return -EOPNOTSUPP;
-
 	if (!(filp->f_mode & FMODE_WRITE))
 		return -EBADF;
 
-- 
2.56.0.317.g454f8302e1-goog