Merge patch series "fs: refactor write_begin/write_end and add ext4 IOCB_DONTCACHE support"

陈涛涛 Taotao Chen <chentaotao@didiglobal.com> says:

This patch series refactors the address_space_operations write_begin()
and write_end() callbacks to take const struct kiocb * as their first
argument, allowing IOCB flags such as IOCB_DONTCACHE to propagate to the
filesystem's buffered I/O path.

Ext4 is updated to implement handling of the IOCB_DONTCACHE flag and
advertises support via the FOP_DONTCACHE file operation flag.

Additionally, the i915 driver's shmem write paths are updated to bypass
the legacy write_begin/write_end interface in favor of directly
calling write_iter() with a constructed synchronous kiocb. Another i915
change replaces a manual write loop with kernel_write() during GEM shmem
object creation.

Tested with ext4 and i915 GEM workloads.

* patches from https://lore.kernel.org/20250716093559.217344-1-chentaotao@didiglobal.com:
  ext4: support uncached buffered I/O
  mm/pagemap: add write_begin_get_folio() helper function
  fs: change write_begin/write_end interface to take struct kiocb *
  drm/i915: Refactor shmem_pwrite() to use kiocb and write_iter
  drm/i915: Use kernel_write() in shmem object create

Link: https://lore.kernel.org/20250716093559.217344-1-chentaotao@didiglobal.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

3 files changed, 35 insertions, 7 deletions

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 178eb90e9cf3..b16b88bfbc3e 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -263,11 +263,11 @@ int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
 int __block_write_begin(struct folio *folio, loff_t pos, unsigned len,
 		get_block_t *get_block);
 int block_write_end(loff_t pos, unsigned len, unsigned copied, struct folio *);
-int generic_write_end(struct file *, struct address_space *,
+int generic_write_end(const struct kiocb *, struct address_space *,
 				loff_t, unsigned len, unsigned copied,
 				struct folio *, void *);
 void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to);
-int cont_write_begin(struct file *, struct address_space *, loff_t,
+int cont_write_begin(const struct kiocb *, struct address_space *, loff_t,
 			unsigned, struct folio **, void **,
 			get_block_t *, loff_t *);
 int generic_cont_expand_simple(struct inode *inode, loff_t size);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 09e3e80b0528..df8c503100c4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -444,10 +444,10 @@ struct address_space_operations {
 
 	void (*readahead)(struct readahead_control *);
 
-	int (*write_begin)(struct file *, struct address_space *mapping,
+	int (*write_begin)(const struct kiocb *, struct address_space *mapping,
 				loff_t pos, unsigned len,
 				struct folio **foliop, void **fsdata);
-	int (*write_end)(struct file *, struct address_space *mapping,
+	int (*write_end)(const struct kiocb *, struct address_space *mapping,
 				loff_t pos, unsigned len, unsigned copied,
 				struct folio *folio, void *fsdata);
 
@@ -3598,9 +3598,10 @@ extern void simple_recursive_removal(struct dentry *,
 extern int noop_fsync(struct file *, loff_t, loff_t, int);
 extern ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
 extern int simple_empty(struct dentry *);
-extern int simple_write_begin(struct file *file, struct address_space *mapping,
-			loff_t pos, unsigned len,
-			struct folio **foliop, void **fsdata);
+extern int simple_write_begin(const struct kiocb *iocb,
+			      struct address_space *mapping,
+			      loff_t pos, unsigned len,
+			      struct folio **foliop, void **fsdata);
 extern const struct address_space_operations ram_aops;
 extern int always_delete_dentry(const struct dentry *);
 extern struct inode *alloc_anon_inode(struct super_block *);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index e63fbfbd5b0f..ce2bcdcadb73 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -751,6 +751,33 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
 		fgf_t fgp_flags, gfp_t gfp);
 
 /**
+ * write_begin_get_folio - Get folio for write_begin with flags.
+ * @iocb: The kiocb passed from write_begin (may be NULL).
+ * @mapping: The address space to search.
+ * @index: The page cache index.
+ * @len: Length of data being written.
+ *
+ * This is a helper for filesystem write_begin() implementations.
+ * It wraps __filemap_get_folio(), setting appropriate flags in
+ * the write begin context.
+ *
+ * Return: A folio or an ERR_PTR.
+ */
+static inline struct folio *write_begin_get_folio(const struct kiocb *iocb,
+		  struct address_space *mapping, pgoff_t index, size_t len)
+{
+        fgf_t fgp_flags = FGP_WRITEBEGIN;
+
+        fgp_flags |= fgf_set_order(len);
+
+        if (iocb && iocb->ki_flags & IOCB_DONTCACHE)
+                fgp_flags |= FGP_DONTCACHE;
+
+        return __filemap_get_folio(mapping, index, fgp_flags,
+                                   mapping_gfp_mask(mapping));
+}
+
+/**
  * filemap_get_folio - Find and get a folio.
  * @mapping: The address_space to search.
  * @index: The page index.