[Cluster-devel] [PATCH 16/17] block: use iomap for writes to block devices

[Christoph Hellwig]

Use iomap in buffer_head compat mode to write to block devices.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 block/Kconfig |  1 +
 block/fops.c  | 33 +++++++++++++++++++++++++++++----
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/block/Kconfig b/block/Kconfig
index 941b2dca70db73..672b08f0096ab4 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -5,6 +5,7 @@
 menuconfig BLOCK
        bool "Enable the block layer" if EXPERT
        default y
+       select IOMAP
        select SBITMAP
        help
         Provide block layer support for the kernel.
diff --git a/block/fops.c b/block/fops.c
index 318247832a7bcf..7910636f8df33b 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -15,6 +15,7 @@
 #include <linux/falloc.h>
 #include <linux/suspend.h>
 #include <linux/fs.h>
+#include <linux/iomap.h>
 #include <linux/module.h>
 #include "blk.h"
 
@@ -386,6 +387,27 @@ static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct 
iov_iter *iter)
        return __blkdev_direct_IO(iocb, iter, bio_max_segs(nr_pages));
 }
 
+static int blkdev_iomap_begin(struct inode *inode, loff_t offset, loff_t 
length,
+               unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
+{
+       struct block_device *bdev = I_BDEV(inode);
+       loff_t isize = i_size_read(inode);
+
+       iomap->bdev = bdev;
+       iomap->offset = ALIGN_DOWN(offset, bdev_logical_block_size(bdev));
+       if (WARN_ON_ONCE(iomap->offset >= isize))
+               return -EIO;
+       iomap->type = IOMAP_MAPPED;
+       iomap->addr = iomap->offset;
+       iomap->length = isize - iomap->offset;
+       iomap->flags |= IOMAP_F_BUFFER_HEAD;
+       return 0;
+}
+
+static const struct iomap_ops blkdev_iomap_ops = {
+       .iomap_begin            = blkdev_iomap_begin,
+};
+
 static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
 {
        return block_write_full_page(page, blkdev_get_block, wbc);
@@ -530,6 +552,11 @@ blkdev_direct_write(struct kiocb *iocb, struct iov_iter 
*from)
        return written;
 }
 
+static ssize_t blkdev_buffered_write(struct kiocb *iocb, struct iov_iter *from)
+{
+       return iomap_file_buffered_write(iocb, from, &blkdev_iomap_ops);
+}
+
 /*
  * Write data to the block device.  Only intended for the block device itself
  * and the raw driver which basically is a fake block device.
@@ -575,16 +602,14 @@ static ssize_t blkdev_write_iter(struct kiocb *iocb, 
struct iov_iter *from)
                iov_iter_truncate(from, size);
        }
 
-       current->backing_dev_info = bdev->bd_disk->bdi;
        if (iocb->ki_flags & IOCB_DIRECT) {
                ret = blkdev_direct_write(iocb, from);
                if (ret >= 0 && iov_iter_count(from))
                        ret = direct_write_fallback(iocb, from, ret,
-                                       generic_perform_write(iocb, from));
+                                       blkdev_buffered_write(iocb, from));
        } else {
-               ret = generic_perform_write(iocb, from);
+               ret = blkdev_buffered_write(iocb, from);
        }
-       current->backing_dev_info = NULL;
 
        if (ret > 0)
                ret = generic_write_sync(iocb, ret);
-- 
2.39.2