A block device driver may choose to provide a rw_page operation.
These will be called when the filesystem is attempting to do page sized
I/O to page cache pages (ie not for direct I/O). This does preclude
I/Os that are larger than page size, so this may only be a performance
gain for some devices.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
---
fs/block_dev.c | 34 ++++++++++++++++++++++++++
fs/mpage.c | 66 ++++++++++++++++++++++++++++++++------------------
include/linux/blkdev.h | 4 +++
3 files changed, 80 insertions(+), 24 deletions(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 1e86823..660557c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -363,6 +363,40 @@ int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
}
EXPORT_SYMBOL(blkdev_fsync);
+int bdev_read_page(struct block_device *bdev, sector_t sector,
+ struct page *page)
+{
+ const struct block_device_operations *ops = bdev->bd_disk->fops;
+ if (!ops->rw_page)
+ return -EOPNOTSUPP;
+ return ops->rw_page(bdev, sector + get_start_sect(bdev), page, READ);
+}
+EXPORT_SYMBOL_GPL(bdev_read_page);
+
+int bdev_write_page(struct block_device *bdev, sector_t sector,
+ struct page *page, struct writeback_control *wbc)
+{
+ int result;
+ int rw = (wbc->sync_mode == WB_SYNC_ALL) ? WRITE_SYNC : WRITE;
+ const struct block_device_operations *ops = bdev->bd_disk->fops;
+ if (!ops->rw_page)
+ return -EOPNOTSUPP;
+ result = ops->rw_page(bdev, sector + get_start_sect(bdev), page, rw);
+ if (result) {
+ if (PageSwapCache(page)) {
+ set_page_dirty(page);
+ ClearPageReclaim(page);
+ end_page_writeback(page);
+ } else {
+ redirty_page_for_writepage(wbc, page);
+ result = 0;
+ }
+ }
+ unlock_page(page);
+ return result;
+}
+EXPORT_SYMBOL_GPL(bdev_write_page);
+
/*
* pseudo-fs
*/
diff --git a/fs/mpage.c b/fs/mpage.c
index 0face1c..b8552ae 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -286,6 +286,11 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
alloc_new:
if (bio == NULL) {
+ if (first_hole == blocks_per_page) {
+ if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9),
+ page))
+ goto out;
+ }
bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
GFP_KERNEL);
@@ -440,6 +445,35 @@ struct mpage_data {
unsigned use_writepage;
};
+/*
+ * We have our BIO, so we can now mark the buffers clean. Make
+ * sure to only clean buffers which we know we'll be writing.
+ */
+static void clean_buffers(struct page *page, unsigned first_unmapped)
+{
+ unsigned buffer_counter = 0;
+ struct buffer_head *bh, *head;
+ if (!page_has_buffers(page))
+ return;
+ head = page_buffers(page);
+ bh = head;
+
+ do {
+ if (buffer_counter++ == first_unmapped)
+ break;
+ clear_buffer_dirty(bh);
+ bh = bh->b_this_page;
+ } while (bh != head);
+
+ /*
+ * we cannot drop the bh if the page is not uptodate or a concurrent
+ * readpage would fail to serialize with the bh and it would read from
+ * disk before we reach the platter.
+ */
+ if (buffer_heads_over_limit && PageUptodate(page))
+ try_to_free_buffers(page);
+}
+
static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
void *data)
{
@@ -575,6 +609,13 @@ page_is_mapped:
alloc_new:
if (bio == NULL) {
+ if (first_unmapped == blocks_per_page) {
+ if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9),
+ page, wbc)) {
+ clean_buffers(page, first_unmapped);
+ goto out;
+ }
+ }
bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
if (bio == NULL)
@@ -592,30 +633,7 @@ alloc_new:
goto alloc_new;
}
- /*
- * OK, we have our BIO, so we can now mark the buffers clean. Make
- * sure to only clean buffers which we know we'll be writing.
- */
- if (page_has_buffers(page)) {
- struct buffer_head *head = page_buffers(page);
- struct buffer_head *bh = head;
- unsigned buffer_counter = 0;
-
- do {
- if (buffer_counter++ == first_unmapped)
- break;
- clear_buffer_dirty(bh);
- bh = bh->b_this_page;
- } while (bh != head);
-
- /*
- * we cannot drop the bh if the page is not uptodate
- * or a concurrent readpage would fail to serialize with the bh
- * and it would read from disk before we reach the platter.
- */
- if (buffer_heads_over_limit && PageUptodate(page))
- try_to_free_buffers(page);
- }
+ clean_buffers(page, first_unmapped);
BUG_ON(PageWriteback(page));
set_page_writeback(page);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1b135d4..50dc979 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1564,6 +1564,7 @@ static inline bool blk_integrity_is_initialized(struct gendisk *g)
struct block_device_operations {
int (*open) (struct block_device *, fmode_t);
void (*release) (struct gendisk *, fmode_t);
+ int (*rw_page)(struct block_device *, sector_t, struct page *, int rw);
int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
int (*direct_access) (struct block_device *, sector_t,
@@ -1582,6 +1583,9 @@ struct block_device_operations {
extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
unsigned long);
+extern int bdev_read_page(struct block_device *, sector_t, struct page *);
+extern int bdev_write_page(struct block_device *, sector_t, struct page *,
+ struct writeback_control *);
#else /* CONFIG_BLOCK */
/*
* stubs for when the block layer is configured out
--
1.8.5.2
--
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