[f2fs-dev] [RFC PATCH v2 06/10] f2fs: prepare mmap write faults for large folios
From: Nanzhe Zhao
Date: Mon Jun 22 2026 - 12:16:14 EST
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 <zhaonanzhe@xxxxxxxxxx>
---
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