iomap: use largest_zero_folio() in iomap_dio_zero()

iomap_dio_zero() uses a custom allocated memory of zeroes for padding
zeroes. This was a temporary solution until there was a way to request a
zero folio that was greater than the PAGE_SIZE.

Use largest_zero_folio() function instead of using the custom allocated
memory of zeroes. There is no guarantee from largest_zero_folio()
function that it will always return a PMD sized folio. Adapt the code so
that it can also work if largest_zero_folio() returns a ZERO_PAGE.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 5d5d63efbd57678f29eb309bd87fbd83633656cc..f8acb41c76d451dce790150ba4aacbec54f9857a 100644 (file)
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -24,13 +24,6 @@
 #define IOMAP_DIO_WRITE                (1U << 30)
 #define IOMAP_DIO_DIRTY                (1U << 31)
 
-/*
- * Used for sub block zeroing in iomap_dio_zero()
- */
-#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
-#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
-static struct page *zero_page;
-
 struct iomap_dio {
        struct kiocb            *iocb;
        const struct iomap_dio_ops *dops;
@@ -285,24 +278,35 @@ static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
 {
        struct inode *inode = file_inode(dio->iocb->ki_filp);
        struct bio *bio;
+       struct folio *zero_folio = largest_zero_folio();
+       int nr_vecs = max(1, i_blocksize(inode) / folio_size(zero_folio));
 
        if (!len)
                return 0;
+
        /*
-        * Max block size supported is 64k
+        * This limit shall never be reached as most filesystems have a
+        * maximum blocksize of 64k.
         */
-       if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE))
+       if (WARN_ON_ONCE(nr_vecs > BIO_MAX_VECS))
                return -EINVAL;
 
-       bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
+       bio = iomap_dio_alloc_bio(iter, dio, nr_vecs,
+                                 REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
        fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
                                  GFP_KERNEL);
        bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
        bio->bi_private = dio;
        bio->bi_end_io = iomap_dio_bio_end_io;
 
-       __bio_add_page(bio, zero_page, len, 0);
+       while (len > 0) {
+               unsigned int io_len = min(len, folio_size(zero_folio));
+
+               bio_add_folio_nofail(bio, zero_folio, io_len, 0);
+               len -= io_len;
+       }
        iomap_dio_submit_bio(iter, dio, bio, pos);
+
        return 0;
 }
 
@@ -825,15 +829,3 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
        return iomap_dio_complete(dio);
 }
 EXPORT_SYMBOL_GPL(iomap_dio_rw);
-
-static int __init iomap_dio_init(void)
-{
-       zero_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
-                               IOMAP_ZERO_PAGE_ORDER);
-
-       if (!zero_page)
-               return -ENOMEM;
-
-       return 0;
-}
-fs_initcall(iomap_dio_init);