[f2fs-dev] [RFC PATCH v2 06/10] f2fs: prepare mmap write faults for large folios

Now write protect `mmap` also need to support large folio,
Change `f2fs_vm_page_mkwrite` to acheive that.

Note it currently marks the whole large folio dirty
to avoid data loss which causes write amplification.
Further optimization is welcome.

Signed-off-by: Nanzhe Zhao <[email protected]>
---
 fs/f2fs/data.c |  2 +-
 fs/f2fs/f2fs.h |  5 +++++
 fs/f2fs/file.c | 55 +++++++++++++++++++++++++++++++++-----------------
 3 files changed, 43 insertions(+), 19 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8485918e1e4c..c37800befa1e 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2540,7 +2540,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 }
 #endif
 
-static struct f2fs_folio_state *ffs_find_or_alloc(struct folio *folio)
+struct f2fs_folio_state *ffs_find_or_alloc(struct folio *folio)
 {
 	struct f2fs_folio_state *ffs;
 	unsigned int nr_subpages = folio_nr_pages(folio);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 2443fa3647d2..1d2e40a42263 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4256,6 +4256,11 @@ int f2fs_write_single_data_page(struct folio *folio, int *submitted,
 				enum iostat_type io_type,
 				int compr_blocks, bool allow_balance);
 bool ffs_test_blk_uptodate(const struct folio *folio, pgoff_t index);
+struct f2fs_folio_state *ffs_find_or_alloc(struct folio *folio);
+void ffs_mark_subrange_dirty(struct folio *folio, size_t offset, size_t len);
+bool ffs_clear_subrange_dirty_and_test(struct folio *folio, size_t offset,
+					size_t len);
+void ffs_clear_subrange_dirty(struct folio *folio, size_t offset, size_t len);
 void f2fs_write_failed(struct inode *inode, loff_t to);
 void f2fs_invalidate_folio(struct folio *folio, size_t offset, size_t length);
 bool f2fs_release_folio(struct folio *folio, gfp_t wait);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 1dddd4b04770..b723e0547fad 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -78,6 +78,13 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct dnode_of_data dn;
 	bool need_alloc = !f2fs_is_pinned_file(inode);
+	pgoff_t pidx = folio->index + folio_page_idx(folio, vmf->page);
+	loff_t pos = (loff_t)pidx << PAGE_SHIFT;
+	loff_t isize;
+	loff_t folio_start;
+	loff_t valid_end;
+	size_t dirty_len;
+	size_t subpage_off;
 	int err = 0;
 	vm_fault_t ret;
 
@@ -114,7 +121,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 
 #ifdef CONFIG_F2FS_FS_COMPRESSION
 	if (f2fs_compressed_file(inode)) {
-		int ret = f2fs_is_compressed_cluster(inode, folio->index);
+		int ret = f2fs_is_compressed_cluster(inode, pidx);
 
 		if (ret < 0) {
 			err = ret;
@@ -132,15 +139,20 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 
 	f2fs_bug_on(sbi, f2fs_has_inline_data(inode));
 
-	f2fs_zero_post_eof_page(inode, (folio->index + 1) << PAGE_SHIFT, true);
-
 	file_update_time(vmf->vma->vm_file);
 	filemap_invalidate_lock_shared(inode->i_mapping);
 
 	folio_lock(folio);
+	isize = i_size_read(inode);
+	folio_start = folio_pos(folio);
+	subpage_off = offset_in_folio(folio, pos);
+	valid_end = min_t(loff_t, folio_start + folio_size(folio), isize);
+	dirty_len = valid_end > folio_start ? valid_end - folio_start : 0;
+
 	if (unlikely(folio->mapping != inode->i_mapping ||
-			folio_pos(folio) > i_size_read(inode) ||
-			!folio_test_uptodate(folio))) {
+			pos >= isize ||
+			!ffs_test_blk_uptodate(folio,
+			folio->index + (subpage_off >> PAGE_SHIFT)))) {
 		folio_unlock(folio);
 		err = -EFAULT;
 		goto out_sem;
@@ -149,9 +161,19 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	if (need_alloc) {
 		/* block allocation */
-		err = f2fs_get_block_locked(&dn, folio->index);
+		if (folio_test_large(folio)) {
+			pgoff_t i, nr = DIV_ROUND_UP(dirty_len, PAGE_SIZE);
+
+			for (i = 0; i < nr; i++) {
+				err = f2fs_get_block_locked(&dn, folio->index + i);
+				if (err)
+					break;
+			}
+		} else {
+			err = f2fs_get_block_locked(&dn, pidx);
+		}
 	} else {
-		err = f2fs_get_dnode_of_data(&dn, folio->index, LOOKUP_NODE);
+		err = f2fs_get_dnode_of_data(&dn, pidx, LOOKUP_NODE);
 		f2fs_put_dnode(&dn);
 		if (f2fs_is_pinned_file(inode) &&
 		    !__is_valid_data_blkaddr(dn.data_blkaddr))
@@ -168,20 +190,17 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	/* wait for GCed page writeback via META_MAPPING */
 	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
 
-	/*
-	 * check to see if the page is mapped already (no holes)
-	 */
-	if (folio_test_mappedtodisk(folio))
-		goto out_sem;
-
 	/* page is wholly or partially inside EOF */
-	if (((loff_t)(folio->index + 1) << PAGE_SHIFT) >
-						i_size_read(inode)) {
-		loff_t offset;
+	if (folio_start + folio_size(folio) > isize) {
+		size_t offset = offset_in_folio(folio, isize);
 
-		offset = i_size_read(inode) & ~PAGE_MASK;
 		folio_zero_segment(folio, offset, folio_size(folio));
 	}
+
+	if (folio_test_large(folio)) {
+		ffs_find_or_alloc(folio);
+		ffs_mark_subrange_dirty(folio, 0, dirty_len);
+	}
 	folio_mark_dirty(folio);
 
 	f2fs_update_iostat(sbi, inode, APP_MAPPED_IO, F2FS_BLKSIZE);
@@ -194,7 +213,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 out:
 	ret = vmf_fs_error(err);
 
-	trace_f2fs_vm_page_mkwrite(inode, folio->index, vmf->vma->vm_flags, ret);
+	trace_f2fs_vm_page_mkwrite(inode, pidx, vmf->vma->vm_flags, ret);
 	return ret;
 }
 
-- 
2.34.1



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