bcachefs: use FGP_WRITEBEGIN instead of combining individual flags

Use FGP_WRITEBEGIN to avoid repeating the individual FGP flags before
starting a buffered write.
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs-io-buffered.c

@@ -677,9 +677,8 @@ int bch2_write_begin(struct file *file, struct address_space *mapping,
 
 	bch2_pagecache_add_get(inode);
 
-	folio = __filemap_get_folio(mapping, pos >> PAGE_SHIFT,
-				FGP_LOCK|FGP_WRITE|FGP_CREAT|FGP_STABLE,
-				mapping_gfp_mask(mapping));
+	folio = __filemap_get_folio(mapping, pos >> PAGE_SHIFT, FGP_WRITEBEGIN,
+				    mapping_gfp_mask(mapping));
 	if (IS_ERR_OR_NULL(folio))
 		goto err_unlock;
 
@@ -820,9 +819,8 @@ static int __bch2_buffered_write(struct bch_inode_info *inode,
 	darray_init(&fs);
 
 	ret = bch2_filemap_get_contig_folios_d(mapping, pos, end,
-				   FGP_LOCK|FGP_WRITE|FGP_STABLE|FGP_CREAT,
-				   mapping_gfp_mask(mapping),
-				   &fs);
+					       FGP_WRITEBEGIN,
+					       mapping_gfp_mask(mapping), &fs);
 	if (ret)
 		goto out;