linux-ext4 - [PATCH v5 5/5] ext4: support uncached buffered I/O

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Message-ID: <20250710101404.362146-6-chentaotao@didiglobal.com>
Date: Thu, 10 Jul 2025 10:14:13 +0000
From: 陈涛涛 Taotao Chen <chentaotao@...iglobal.com>
To: "tytso@....edu" <tytso@....edu>, "hch@...radead.org" <hch@...radead.org>,
	"adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>, "willy@...radead.org"
	<willy@...radead.org>, "brauner@...nel.org" <brauner@...nel.org>,
	"jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>,
	"rodrigo.vivi@...el.com" <rodrigo.vivi@...el.com>, "tursulin@...ulin.net"
	<tursulin@...ulin.net>, "airlied@...il.com" <airlied@...il.com>
CC: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "chentao325@...com" <chentao325@...com>,
	"frank.li@...o.com" <frank.li@...o.com>,
	陈涛涛 Taotao Chen <chentaotao@...iglobal.com>
Subject: [PATCH v5 5/5] ext4: support uncached buffered I/O

From: Taotao Chen <chentaotao@...iglobal.com>

Set FOP_DONTCACHE in ext4_file_operations to declare support for
uncached buffered I/O.

To handle this flag, update ext4_write_begin() and ext4_da_write_begin()
to use write_begin_get_folio(), which encapsulates FGP_DONTCACHE logic
based on iocb->ki_flags.

Part of a series refactoring address_space_operations write_begin and
write_end callbacks to use struct kiocb for passing write context and
flags.

Signed-off-by: Taotao Chen <chentaotao@...iglobal.com>
---
 fs/ext4/file.c  |  3 ++-
 fs/ext4/inode.c | 12 +++---------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 21df81347147..274b41a476c8 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -977,7 +977,8 @@ const struct file_operations ext4_file_operations = {
 	.splice_write	= iter_file_splice_write,
 	.fallocate	= ext4_fallocate,
 	.fop_flags	= FOP_MMAP_SYNC | FOP_BUFFER_RASYNC |
-			  FOP_DIO_PARALLEL_WRITE,
+			  FOP_DIO_PARALLEL_WRITE |
+			  FOP_DONTCACHE,
 };
 
 const struct inode_operations ext4_file_inode_operations = {
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9a16efd072bb..5c7024051f1e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1264,7 +1264,6 @@ static int ext4_write_begin(const struct kiocb *iocb,
 	struct folio *folio;
 	pgoff_t index;
 	unsigned from, to;
-	fgf_t fgp = FGP_WRITEBEGIN;
 
 	ret = ext4_emergency_state(inode->i_sb);
 	if (unlikely(ret))
@@ -1288,16 +1287,14 @@ static int ext4_write_begin(const struct kiocb *iocb,
 	}
 
 	/*
-	 * __filemap_get_folio() can take a long time if the
+	 * write_begin_get_folio() can take a long time if the
 	 * system is thrashing due to memory pressure, or if the folio
 	 * is being written back.  So grab it first before we start
 	 * the transaction handle.  This also allows us to allocate
 	 * the folio (if needed) without using GFP_NOFS.
 	 */
 retry_grab:
-	fgp |= fgf_set_order(len);
-	folio = __filemap_get_folio(mapping, index, fgp,
-				    mapping_gfp_mask(mapping));
+	folio = write_begin_get_folio(iocb, mapping, index, len);
 	if (IS_ERR(folio))
 		return PTR_ERR(folio);
 
@@ -3046,7 +3043,6 @@ static int ext4_da_write_begin(const struct kiocb *iocb,
 	struct folio *folio;
 	pgoff_t index;
 	struct inode *inode = mapping->host;
-	fgf_t fgp = FGP_WRITEBEGIN;
 
 	ret = ext4_emergency_state(inode->i_sb);
 	if (unlikely(ret))
@@ -3072,9 +3068,7 @@ static int ext4_da_write_begin(const struct kiocb *iocb,
 	}
 
 retry:
-	fgp |= fgf_set_order(len);
-	folio = __filemap_get_folio(mapping, index, fgp,
-				    mapping_gfp_mask(mapping));
+	folio = write_begin_get_folio(iocb, mapping, index, len);
 	if (IS_ERR(folio))
 		return PTR_ERR(folio);
 
-- 
2.34.1