shmem: convert shmem_file_read_iter() to use shmem_get_folio()

Use a folio throughout, saving five calls to compound_head().

Link: https://lkml.kernel.org/r/20220902194653.1739778-28-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index c69b53602a1d85282ebe1faeb64be68bbcf5553a..0f81193128470b6c0550e9d3ddf1055b92c913e3 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2577,6 +2577,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
        offset = *ppos & ~PAGE_MASK;
 
        for (;;) {
+               struct folio *folio = NULL;
                struct page *page = NULL;
                pgoff_t end_index;
                unsigned long nr, ret;
@@ -2591,17 +2592,18 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
                                break;
                }
 
-               error = shmem_getpage(inode, index, &page, SGP_READ);
+               error = shmem_get_folio(inode, index, &folio, SGP_READ);
                if (error) {
                        if (error == -EINVAL)
                                error = 0;
                        break;
                }
-               if (page) {
-                       unlock_page(page);
+               if (folio) {
+                       folio_unlock(folio);
 
+                       page = folio_file_page(folio, index);
                        if (PageHWPoison(page)) {
-                               put_page(page);
+                               folio_put(folio);
                                error = -EIO;
                                break;
                        }
@@ -2617,14 +2619,14 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
                if (index == end_index) {
                        nr = i_size & ~PAGE_MASK;
                        if (nr <= offset) {
-                               if (page)
-                                       put_page(page);
+                               if (folio)
+                                       folio_put(folio);
                                break;
                        }
                }
                nr -= offset;
 
-               if (page) {
+               if (folio) {
                        /*
                         * If users can be writing to this page using arbitrary
                         * virtual addresses, take care about potential aliasing
@@ -2636,13 +2638,13 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
                         * Mark the page accessed if we read the beginning.
                         */
                        if (!offset)
-                               mark_page_accessed(page);
+                               folio_mark_accessed(folio);
                        /*
                         * Ok, we have the page, and it's up-to-date, so
                         * now we can copy it to user space...
                         */
                        ret = copy_page_to_iter(page, offset, nr, to);
-                       put_page(page);
+                       folio_put(folio);
 
                } else if (user_backed_iter(to)) {
                        /*