vfs: add hooks for ext4's delayed allocation support

Export mpage_bio_submit() and __mpage_writepage() for the benefit of
ext4's delayed allocation support.   Also change __block_write_full_page
so that if buffers that have the BH_Delay flag set it will call
get_block() to get the physical block allocated, just as in the
!BH_Mapped case.

Signed-off-by: Alex Tomas <alex@clusterfs.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

3 files changed, 20 insertions, 11 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index f4b033237a02..5fa1512cd9a2 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1691,11 +1691,13 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
                          */
                         clear_buffer_dirty(bh);
                         set_buffer_uptodate(bh);
-                } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
+                } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
+                           buffer_dirty(bh)) {
                         WARN_ON(bh->b_size != blocksize);
                         err = get_block(inode, block, bh, 1);
                         if (err)
                                 goto recover;
+                        clear_buffer_delay(bh);
                         if (buffer_new(bh)) {
                                 /* blockdev mappings never come here */
                                 clear_buffer_new(bh);
@@ -1774,7 +1776,8 @@ recover:
         bh = head;
         /* Recovery: lock and submit the mapped buffers */
         do {
-                if (buffer_mapped(bh) && buffer_dirty(bh)) {
+                if (buffer_mapped(bh) && buffer_dirty(bh) &&
+                    !buffer_delay(bh)) {
                         lock_buffer(bh);
                         mark_buffer_async_write(bh);
                 } else {
diff --git a/fs/mpage.c b/fs/mpage.c
index 235e4d3873a8..dbcc7af76a15 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -82,7 +82,7 @@ static void mpage_end_io_write(struct bio *bio, int err)
         bio_put(bio);
 }
 
-static struct bio *mpage_bio_submit(int rw, struct bio *bio)
+struct bio *mpage_bio_submit(int rw, struct bio *bio)
 {
         bio->bi_end_io = mpage_end_io_read;
         if (rw == WRITE)
@@ -90,6 +90,7 @@ static struct bio *mpage_bio_submit(int rw, struct bio *bio)
         submit_bio(rw, bio);
         return NULL;
 }
+EXPORT_SYMBOL(mpage_bio_submit);
 
 static struct bio *
 mpage_alloc(struct block_device *bdev,
@@ -435,15 +436,9 @@ EXPORT_SYMBOL(mpage_readpage);
  * written, so it can intelligently allocate a suitably-sized BIO.  For now,
  * just allocate full-size (16-page) BIOs.
  */
-struct mpage_data {
-        struct bio *bio;
-        sector_t last_block_in_bio;
-        get_block_t *get_block;
-        unsigned use_writepage;
-};
 
-static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
-                             void *data)
+int __mpage_writepage(struct page *page, struct writeback_control *wbc,
+                      void *data)
 {
         struct mpage_data *mpd = data;
         struct bio *bio = mpd->bio;
@@ -651,6 +646,7 @@ out:
         mpd->bio = bio;
         return ret;
 }
+EXPORT_SYMBOL(__mpage_writepage);
 
 /**
  * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
diff --git a/include/linux/mpage.h b/include/linux/mpage.h
index 068a0c9946af..5c42821da2d1 100644
--- a/include/linux/mpage.h
+++ b/include/linux/mpage.h
@@ -11,11 +11,21 @@
  */
 #ifdef CONFIG_BLOCK
 
+struct mpage_data {
+        struct bio *bio;
+        sector_t last_block_in_bio;
+        get_block_t *get_block;
+        unsigned use_writepage;
+};
+
 struct writeback_control;
 
+struct bio *mpage_bio_submit(int rw, struct bio *bio);
 int mpage_readpages(struct address_space *mapping, struct list_head *pages,
                                 unsigned nr_pages, get_block_t get_block);
 int mpage_readpage(struct page *page, get_block_t get_block);
+int __mpage_writepage(struct page *page, struct writeback_control *wbc,
+                      void *data);
 int mpage_writepages(struct address_space *mapping,
                 struct writeback_control *wbc, get_block_t get_block);
 int mpage_writepage(struct page *page, get_block_t *get_block,