[PATCH v2 2/2] f2fs: enable buffered RWF_DONTCACHE

[Wenjie Qi]

Pass FGP_DONTCACHE to f2fs_filemap_get_folio() for IOCB_DONTCACHE writes
and advertise FOP_DONTCACHE.

Keep the F2FS-specific lookup flags because write_begin_get_folio() adds
FGP_STABLE, which can deadlock here.

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 774a3e2d8e3..ebd9dc582f9 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3981,11 +3981,15 @@ static int f2fs_write_begin(const struct kiocb *iocb,
 	struct inode *inode = mapping->host;
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct folio *folio;
+	fgf_t fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT;
 	pgoff_t index = pos >> PAGE_SHIFT;
 	bool need_balance = false;
 	block_t blkaddr = NULL_ADDR;
 	int err = 0;
 
+	if (iocb->ki_flags & IOCB_DONTCACHE)
+		fgp_flags |= FGP_DONTCACHE;
+
 	trace_f2fs_write_begin(inode, pos, len);
 
 	if (!f2fs_is_checkpoint_ready(sbi)) {
@@ -4031,9 +4035,8 @@ static int f2fs_write_begin(const struct kiocb *iocb,
 	 * 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));
+	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 a54b3ab52f1..08285c07c2d 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -5911,6 +5911,6 @@ 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