[PATCH RFC v3 for-6.8/block 10/17] cramfs: use bdev apis in cramfs_blkdev_read()

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

On the one hand covert to use folio while reading bdev inode, on the
other hand prevent to access bd_inode directly.

Also do some cleanup that there is no need for two for loop, and remove
local array pages.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 fs/cramfs/inode.c | 36 +++++++++++++-----------------------
 1 file changed, 13 insertions(+), 23 deletions(-)

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index 60dbfa0f8805..fad95d683d97 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -183,9 +183,6 @@ static int next_buffer;
 static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
                                unsigned int len)
 {
-       struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
-       struct file_ra_state ra = {};
-       struct page *pages[BLKS_PER_BUF];
        unsigned i, blocknr, buffer;
        unsigned long devsize;
        char *data;
@@ -214,37 +211,30 @@ static void *cramfs_blkdev_read(struct super_block *sb, 
unsigned int offset,
        devsize = bdev_nr_bytes(sb->s_bdev) >> PAGE_SHIFT;
 
        /* Ok, read in BLKS_PER_BUF pages completely first. */
-       file_ra_state_init(&ra, mapping);
-       page_cache_sync_readahead(mapping, &ra, NULL, blocknr, BLKS_PER_BUF);
-
-       for (i = 0; i < BLKS_PER_BUF; i++) {
-               struct page *page = NULL;
-
-               if (blocknr + i < devsize) {
-                       page = read_mapping_page(mapping, blocknr + i, NULL);
-                       /* synchronous error? */
-                       if (IS_ERR(page))
-                               page = NULL;
-               }
-               pages[i] = page;
-       }
+       bdev_sync_readahead(sb->s_bdev, NULL, NULL, blocknr, BLKS_PER_BUF);
 
        buffer = next_buffer;
        next_buffer = NEXT_BUFFER(buffer);
        buffer_blocknr[buffer] = blocknr;
        buffer_dev[buffer] = sb;
-
        data = read_buffers[buffer];
+
        for (i = 0; i < BLKS_PER_BUF; i++) {
-               struct page *page = pages[i];
+               struct folio *folio = NULL;
+
+               if (blocknr + i < devsize)
+                       folio = bdev_read_folio(sb->s_bdev,
+                                               (blocknr + i) << PAGE_SHIFT);
 
-               if (page) {
-                       memcpy_from_page(data, page, 0, PAGE_SIZE);
-                       put_page(page);
-               } else
+               if (IS_ERR_OR_NULL(folio)) {
                        memset(data, 0, PAGE_SIZE);
+               } else {
+                       memcpy_from_folio(data, folio, 0, PAGE_SIZE);
+                       folio_put(folio);
+               }
                data += PAGE_SIZE;
        }
+
        return read_buffers[buffer] + offset;
 }
 
-- 
2.39.2