ext4: replace ext4_writepage_trans_blocks()

After ext4 supports large folios, the semantics of reserving credits in
pages is no longer applicable. In most scenarios, reserving credits in
extents is sufficient. Therefore, introduce ext4_chunk_trans_extent()
to replace ext4_writepage_trans_blocks(). move_extent_per_page() is the
only remaining location where we are still processing extents in pages.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250707140814.542883-10-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: zhangyi089

fs/ext4/ext4.h

@@ -3064,9 +3064,9 @@ extern int ext4_punch_hole(struct file *file, loff_t offset, loff_t length);
 extern void ext4_set_inode_flags(struct inode *, bool init);
 extern int ext4_alloc_da_blocks(struct inode *inode);
 extern void ext4_set_aops(struct inode *inode);
-extern int ext4_writepage_trans_blocks(struct inode *);
 extern int ext4_normal_submit_inode_data_buffers(struct jbd2_inode *jinode);
 extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
+extern int ext4_chunk_trans_extent(struct inode *inode, int nrblocks);
 extern int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
 				  int pextents);
 extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,

fs/ext4/extents.c

@@ -5171,7 +5171,7 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
 				credits = depth + 2;
 			}
 
-			restart_credits = ext4_writepage_trans_blocks(inode);
+			restart_credits = ext4_chunk_trans_extent(inode, 0);
 			err = ext4_datasem_ensure_credits(handle, inode, credits,
 					restart_credits, 0);
 			if (err) {
@@ -5431,7 +5431,7 @@ static int ext4_collapse_range(struct file *file, loff_t offset, loff_t len)
 
 	truncate_pagecache(inode, start);
 
-	credits = ext4_writepage_trans_blocks(inode);
+	credits = ext4_chunk_trans_extent(inode, 0);
 	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
@@ -5527,7 +5527,7 @@ static int ext4_insert_range(struct file *file, loff_t offset, loff_t len)
 
 	truncate_pagecache(inode, start);
 
-	credits = ext4_writepage_trans_blocks(inode);
+	credits = ext4_chunk_trans_extent(inode, 0);
 	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);

fs/ext4/inline.c

@@ -562,7 +562,7 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
 		return 0;
 	}
 
-	needed_blocks = ext4_writepage_trans_blocks(inode);
+	needed_blocks = ext4_chunk_trans_extent(inode, 1);
 
 	ret = ext4_get_inode_loc(inode, &iloc);
 	if (ret)
@@ -1864,7 +1864,7 @@ int ext4_inline_data_truncate(struct inode *inode, int *has_inline)
 	};
 
 
-	needed_blocks = ext4_writepage_trans_blocks(inode);
+	needed_blocks = ext4_chunk_trans_extent(inode, 1);
 	handle = ext4_journal_start(inode, EXT4_HT_INODE, needed_blocks);
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
@@ -1979,7 +1979,7 @@ int ext4_convert_inline_data(struct inode *inode)
 			return 0;
 	}
 
-	needed_blocks = ext4_writepage_trans_blocks(inode);
+	needed_blocks = ext4_chunk_trans_extent(inode, 1);
 
 	iloc.bh = NULL;
 	error = ext4_get_inode_loc(inode, &iloc);

fs/ext4/inode.c

@@ -1294,7 +1294,8 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
 	 * Reserve one block more for addition to orphan list in case
 	 * we allocate blocks but write fails for some reason
 	 */
-	needed_blocks = ext4_writepage_trans_blocks(inode) + 1;
+	needed_blocks = ext4_chunk_trans_extent(inode,
+			ext4_journal_blocks_per_folio(inode)) + 1;
 	index = pos >> PAGE_SHIFT;
 
 	if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) {
@@ -4461,7 +4462,7 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
 		return ret;
 
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
-		credits = ext4_writepage_trans_blocks(inode);
+		credits = ext4_chunk_trans_extent(inode, 2);
 	else
 		credits = ext4_blocks_for_truncate(inode);
 	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
@@ -4610,7 +4611,7 @@ int ext4_truncate(struct inode *inode)
 	}
 
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
-		credits = ext4_writepage_trans_blocks(inode);
+		credits = ext4_chunk_trans_extent(inode, 1);
 	else
 		credits = ext4_blocks_for_truncate(inode);
 
@@ -6237,25 +6238,19 @@ int ext4_meta_trans_blocks(struct inode *inode, int lblocks, int pextents)
 }
 
 /*
- * Calculate the total number of credits to reserve to fit
- * the modification of a single pages into a single transaction,
- * which may include multiple chunks of block allocations.
- *
- * This could be called via ext4_write_begin()
- *
- * We need to consider the worse case, when
- * one new block per extent.
+ * Calculate the journal credits for modifying the number of blocks
+ * in a single extent within one transaction. 'nrblocks' is used only
+ * for non-extent inodes. For extent type inodes, 'nrblocks' can be
+ * zero if the exact number of blocks is unknown.
  */
-int ext4_writepage_trans_blocks(struct inode *inode)
+int ext4_chunk_trans_extent(struct inode *inode, int nrblocks)
 {
-	int bpp = ext4_journal_blocks_per_folio(inode);
 	int ret;
 
-	ret = ext4_meta_trans_blocks(inode, bpp, bpp);
-
+	ret = ext4_meta_trans_blocks(inode, nrblocks, 1);
 	/* Account for data blocks for journalled mode */
 	if (ext4_should_journal_data(inode))
-		ret += bpp;
+		ret += nrblocks;
 	return ret;
 }
 
@@ -6633,10 +6628,12 @@ static int ext4_block_page_mkwrite(struct inode *inode, struct folio *folio,
 	handle_t *handle;
 	loff_t size;
 	unsigned long len;
+	int credits;
 	int ret;
 
-	handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE,
-				    ext4_writepage_trans_blocks(inode));
+	credits = ext4_chunk_trans_extent(inode,
+			ext4_journal_blocks_per_folio(inode));
+	handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE, credits);
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
 

fs/ext4/move_extent.c

@@ -280,7 +280,8 @@ move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
 	 */
 again:
 	*err = 0;
-	jblocks = ext4_writepage_trans_blocks(orig_inode) * 2;
+	jblocks = ext4_meta_trans_blocks(orig_inode, block_len_in_page,
+					 block_len_in_page) * 2;
 	handle = ext4_journal_start(orig_inode, EXT4_HT_MOVE_EXTENTS, jblocks);
 	if (IS_ERR(handle)) {
 		*err = PTR_ERR(handle);

fs/ext4/xattr.c

@@ -962,7 +962,7 @@ int __ext4_xattr_set_credits(struct super_block *sb, struct inode *inode,
 	 * so we need to reserve credits for this eventuality
 	 */
 	if (inode && ext4_has_inline_data(inode))
-		credits += ext4_writepage_trans_blocks(inode) + 1;
+		credits += ext4_chunk_trans_extent(inode, 1) + 1;
 
 	/* We are done if ea_inode feature is not enabled. */
 	if (!ext4_has_feature_ea_inode(sb))