fuse: support folios in struct fuse_args_pages and fuse_copy_pages()

This adds support in struct fuse_args_pages and fuse_copy_pages() for
using folios instead of pages for transferring data. Both folios and
pages must be supported right now in struct fuse_args_pages and
fuse_copy_pages() until all request types have been converted to use
folios. Once all have been converted, then
struct fuse_args_pages and fuse_copy_pages() will only support folios.

Right now in fuse, all folios are one page (large folios are not yet
supported). As such, copying folio->page is sufficient for copying
the entire folio in fuse_copy_pages().

No functional changes.

Signed-off-by: Joanne Koong <[email protected]>
Reviewed-by: Josef Bacik <[email protected]>
Signed-off-by: Miklos Szeredi <[email protected]>

Author: joannekoong

fs/fuse/dev.c

@@ -1028,17 +1028,41 @@ static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
 	struct fuse_req *req = cs->req;
 	struct fuse_args_pages *ap = container_of(req->args, typeof(*ap), args);
 
+	if (ap->uses_folios) {
+		for (i = 0; i < ap->num_folios && (nbytes || zeroing); i++) {
+			int err;
+			unsigned int offset = ap->folio_descs[i].offset;
+			unsigned int count = min(nbytes, ap->folio_descs[i].length);
+			struct page *orig, *pagep;
 
-	for (i = 0; i < ap->num_pages && (nbytes || zeroing); i++) {
-		int err;
-		unsigned int offset = ap->descs[i].offset;
-		unsigned int count = min(nbytes, ap->descs[i].length);
+			orig = pagep = &ap->folios[i]->page;
 
-		err = fuse_copy_page(cs, &ap->pages[i], offset, count, zeroing);
-		if (err)
-			return err;
+			err = fuse_copy_page(cs, &pagep, offset, count, zeroing);
+			if (err)
+				return err;
+
+			nbytes -= count;
+
+			/*
+			 *  fuse_copy_page may have moved a page from a pipe
+			 *  instead of copying into our given page, so update
+			 *  the folios if it was replaced.
+			 */
+			if (pagep != orig)
+				ap->folios[i] = page_folio(pagep);
+		}
+	} else {
+		for (i = 0; i < ap->num_pages && (nbytes || zeroing); i++) {
+			int err;
+			unsigned int offset = ap->descs[i].offset;
+			unsigned int count = min(nbytes, ap->descs[i].length);
 
-		nbytes -= count;
+			err = fuse_copy_page(cs, &ap->pages[i], offset, count, zeroing);
+			if (err)
+				return err;
+
+			nbytes -= count;
+		}
 	}
 	return 0;
 }

fs/fuse/fuse_i.h

@@ -291,6 +291,12 @@ struct fuse_page_desc {
 	unsigned int offset;
 };
 
+/** FUSE folio descriptor */
+struct fuse_folio_desc {
+	unsigned int length;
+	unsigned int offset;
+};
+
 struct fuse_args {
 	uint64_t nodeid;
 	uint32_t opcode;
@@ -319,9 +325,19 @@ struct fuse_args {
 
 struct fuse_args_pages {
 	struct fuse_args args;
-	struct page **pages;
-	struct fuse_page_desc *descs;
-	unsigned int num_pages;
+	union {
+		struct {
+			struct page **pages;
+			struct fuse_page_desc *descs;
+			unsigned int num_pages;
+		};
+		struct {
+			struct folio **folios;
+			struct fuse_folio_desc *folio_descs;
+			unsigned int num_folios;
+		};
+	};
+	bool uses_folios;
 };
 
 struct fuse_release_args {