[RFC PATCH 2/2] f2fs: enable buffered RWF_DONTCACHE

[Wenjie Qi]

Expose FOP_DONTCACHE and propagate IOCB_DONTCACHE
to write_begin folio allocation so buffered
RWF_DONTCACHE can reach the F2FS write path.

The write-side completion and bio-isolation
semantics are prepared by the previous patch in
this RFC series.

Signed-off-by: Wenjie Qi <qiwenjie@xxxxxxxxxx>
---
 fs/f2fs/data.c | 9 ++++++---
 fs/f2fs/file.c | 2 +-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8a1e407..40c8f7a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3982,6 +3982,7 @@ static int f2fs_write_begin(const struct kiocb *iocb,
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct folio *folio;
 	pgoff_t index = pos >> PAGE_SHIFT;
+	fgf_t fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT;
 	bool need_balance = false;
 	block_t blkaddr = NULL_ADDR;
 	int err = 0;
@@ -4031,9 +4032,11 @@ repeat:
 	 * Do not use FGP_STABLE to avoid deadlock.
 	 * Will wait that below with our IO control.
 	 */
-	folio = f2fs_filemap_get_folio(mapping, index,
-				FGP_LOCK | FGP_WRITE | FGP_CREAT,
-				mapping_gfp_mask(mapping));
+	if (iocb && (iocb->ki_flags & IOCB_DONTCACHE))
+		fgp_flags |= FGP_DONTCACHE;
+
+	folio = f2fs_filemap_get_folio(mapping, index, fgp_flags,
+				       mapping_gfp_mask(mapping));
 	if (IS_ERR(folio)) {
 		err = PTR_ERR(folio);
 		goto fail;
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index b99d9cd..b3d1684 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -5578,6 +5578,6 @@ const struct file_operations f2fs_file_operations = {
 	.splice_read	= f2fs_file_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.fadvise	= f2fs_file_fadvise,
-	.fop_flags	= FOP_BUFFER_RASYNC,
+	.fop_flags	= FOP_BUFFER_RASYNC | FOP_DONTCACHE,
 	.setlease	= generic_setlease,
 };
-- 
2.43.0