[PATCH v8 15/15] f2fs: make compressed files compatible with large folio

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

From: Nanzhe Zhao <zhaonanzhe@xiaomi.com>

The compression flag is the hint indicates that the inode can be
compressed, when the inode is using large folio, we expected it keeps
using the large folio read/write paths and its data stays uncompressed
on disk until the inode is evicted and re-read

Let f2fs_write_begin() skip the compression overwrite preparation for
such inodes and remove the compressed-file gate in
f2fs_read_data_large_folio() so the data is simply read/written as
regular blocks.

For the same reason, reject F2FS_IOC_COMPRESS_FILE with -EOPNOTSUPP
once the inode mapping is switched to large folios.

Signed-off-by: Nanzhe Zhao <zhaonanzhe@xiaomi.com>
---
 Documentation/filesystems/f2fs.rst | 10 ++++++++
 fs/f2fs/compress.c                 |  2 ++
 fs/f2fs/data.c                     |  9 ++-----
 fs/f2fs/file.c                     | 38 ++++++++++++++++++++++++++++++
 4 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
index 55798421f2c4..b79bb67ee78e 100644
--- a/Documentation/filesystems/f2fs.rst
+++ b/Documentation/filesystems/f2fs.rst
@@ -942,6 +942,16 @@ Compression implementation
   reserved via ioctl(F2FS_IOC_RESERVE_COMPRESS_BLOCKS) or the file size is
   truncated to zero.
 
+- Compression and large folios are not effective at the same time on a file:
+  a compressed inode does not use large folios, while an inode which is
+  using large folios keeps its data uncompressed on disk.  If the compression
+  flag is set on an inode that is already using large folios, the flag works
+  as a hint until the inode is evicted: the inode keeps using the large folio
+  read/write paths, f2fs_write_begin() skips the compression overwrite
+  preparation, and ioctl(F2FS_IOC_COMPRESS_FILE) fails with -EOPNOTSUPP.
+  Once the inode is evicted and read back, it uses order-0 folios again and
+  compression is applied as usual.
+
 Compress metadata layout::
 
 				[Dnode Structure]
diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 162bd8ef822a..721b01dd0d24 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -78,6 +78,8 @@ bool f2fs_is_compressed_page(struct folio *folio)
 		return false;
 	if (folio_test_f2fs_nonpointer(folio))
 		return false;
+	if (f2fs_folio_has_ffs(folio))
+		return false;
 
 	f2fs_bug_on(F2FS_F_SB(folio),
 		*((u32 *)folio->private) != F2FS_COMPRESSED_PAGE_MAGIC);
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index cc3c9e51db9c..ab8f5b44d63a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3288,12 +3288,6 @@ static int f2fs_read_data_large_folio(struct inode *inode,
 	int ret = 0;
 	bool folio_in_bio = false;
 
-	if (f2fs_compressed_file(inode)) {
-		if (folio)
-			folio_unlock(folio);
-		return -EOPNOTSUPP;
-	}
-
 	map.m_seg_type = NO_CHECK_TYPE;
 
 	if (rac)
@@ -5331,7 +5325,8 @@ static int f2fs_write_begin(const struct kiocb *iocb,
 	}
 
 #ifdef CONFIG_F2FS_FS_COMPRESSION
-	if (f2fs_compressed_file(inode)) {
+	if (f2fs_compressed_file(inode) &&
+	    !mapping_large_folio_support(inode->i_mapping)) {
 		int ret;
 		struct page *page;
 
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 15bea642e986..cb7a9d4227f4 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4907,6 +4907,7 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 	struct address_space *mapping = inode->i_mapping;
 	struct folio *folio;
 	pgoff_t redirty_idx = page_idx;
+	pgoff_t end_idx = page_idx + len;
 	int page_len = 0, ret = 0;
 
 	filemap_invalidate_lock_shared(mapping);
@@ -4924,6 +4925,9 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 	} while (page_len < len);
 
 	while (redirty_idx < page_idx) {
+		pgoff_t next_idx;
+		size_t off, dlen;
+
 		folio = filemap_lock_folio(mapping, redirty_idx);
 
 		/* It will never fail, when folio has pinned above */
@@ -4931,6 +4935,33 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 
 		f2fs_folio_wait_writeback(folio, true, true);
 
+		/*
+		 * Only this cluster is rewritten, while a large folio can
+		 * cover more than one cluster, so mark the intersection of
+		 * the folio and [redirty_idx, end_idx).
+		 */
+		next_idx = min_t(pgoff_t, folio_next_index(folio), end_idx);
+		off = offset_in_folio(folio, (loff_t)redirty_idx << PAGE_SHIFT);
+		dlen = (size_t)(next_idx - redirty_idx) << PAGE_SHIFT;
+
+		if (folio_test_large(folio)) {
+			/*
+			 * A compressed inode can keep using large folios, in
+			 * which case the compression flag only works as a hint
+			 * until the inode is evicted.  Update the subpage dirty
+			 * bitmap as well, otherwise f2fs_write_cache_folios()
+			 * finds no dirty range and skips the whole folio.
+			 */
+			if (!f2fs_ffs_find_or_alloc(folio)) {
+				ret = -ENOMEM;
+				folio_unlock(folio);
+				folio_put_refs(folio, 2);
+				redirty_idx = folio_next_index(folio);
+				continue;
+			}
+			f2fs_ffs_mark_subrange_dirty(folio, off, dlen);
+		}
+
 		folio_mark_dirty(folio);
 		folio_set_f2fs_gcing(folio);
 		redirty_idx = folio_next_index(folio);
@@ -5037,6 +5068,13 @@ static int f2fs_ioc_compress_file(struct file *filp)
 	if (!(filp->f_mode & FMODE_WRITE))
 		return -EBADF;
 
+	/*
+	 * The mapping is already using large folios, where the data is kept
+	 * uncompressed, so refuse to start compressing the file.
+	 */
+	if (mapping_large_folio_support(inode->i_mapping))
+		return -EOPNOTSUPP;
+
 	f2fs_balance_fs(sbi, true);
 
 	ret = mnt_want_write_file(filp);
-- 
2.43.0