[PATCH 1/2] direct IO: respect backing device max IO size

[stockhausen]

blkdev_direct_IO() and __blkdev_direct_IO() currently calculate the maximum
number of IO pages independently. This is no problem as they both rely on
BIO_MAX_PAGES. The forthcoming patch will provide a modified calculation
scheme. Make the internal function dependent from the caller to have only
one single source of truth.

Signed-off-by: Markus Stockhausen stockhau...@collogia.de

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7ec920e..2f777f9 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -317,7 +317,8 @@ static void blkdev_bio_end_io(struct bio *bio)
 }
 
 static ssize_t
-__blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
+__blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages,
+               int max_io_pages)
 {
        struct file *file = iocb->ki_filp;
        struct inode *inode = bdev_file_inode(file);
@@ -375,7 +376,7 @@ static void blkdev_bio_end_io(struct bio *bio)
                dio->size += bio->bi_iter.bi_size;
                pos += bio->bi_iter.bi_size;
 
-               nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
+               nr_pages = iov_iter_npages(iter, max_io_pages);
                if (!nr_pages) {
                        qc = submit_bio(bio);
                        break;
@@ -427,7 +428,7 @@ static void blkdev_bio_end_io(struct bio *bio)
        if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
                return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
 
-       return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES));
+       return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES), 
BIO_MAX_PAGES);
 }
 
 static __init int blkdev_init(void)
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