nilfs2: segment constructor

This adds the segment constructor (also called log writer).

The segment constructor collects dirty buffers for every dirty inode,
makes summaries of the buffers, assigns disk block addresses to the
buffers, and then submits BIOs for the buffers.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 59 insertions, 3 deletions

diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
index 7ddd42e24f77..8031086db8d5 100644
--- a/fs/nilfs2/file.c
+++ b/fs/nilfs2/file.c
@@ -73,10 +73,66 @@ nilfs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
         return ret;
 }
 
-static int nilfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
+static int nilfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
-        if (!(vma->vm_flags & (VM_WRITE | VM_MAYWRITE)))
-                return -EPERM;
+        struct page *page = vmf->page;
+        struct inode *inode = vma->vm_file->f_dentry->d_inode;
+        struct nilfs_transaction_info ti;
+        int ret;
+
+        if (unlikely(nilfs_near_disk_full(NILFS_SB(inode->i_sb)->s_nilfs)))
+                return VM_FAULT_SIGBUS; /* -ENOSPC */
+
+        lock_page(page);
+        if (page->mapping != inode->i_mapping ||
+            page_offset(page) >= i_size_read(inode) || !PageUptodate(page)) {
+                unlock_page(page);
+                return VM_FAULT_NOPAGE; /* make the VM retry the fault */
+        }
+
+        /*
+         * check to see if the page is mapped already (no holes)
+         */
+        if (PageMappedToDisk(page)) {
+                unlock_page(page);
+                goto mapped;
+        }
+        if (page_has_buffers(page)) {
+                struct buffer_head *bh, *head;
+                int fully_mapped = 1;
+
+                bh = head = page_buffers(page);
+                do {
+                        if (!buffer_mapped(bh)) {
+                                fully_mapped = 0;
+                                break;
+                        }
+                } while (bh = bh->b_this_page, bh != head);
+
+                if (fully_mapped) {
+                        SetPageMappedToDisk(page);
+                        unlock_page(page);
+                        goto mapped;
+                }
+        }
+        unlock_page(page);
+
+        /*
+         * fill hole blocks
+         */
+        ret = nilfs_transaction_begin(inode->i_sb, &ti, 1);
+        /* never returns -ENOMEM, but may return -ENOSPC */
+        if (unlikely(ret))
+                return VM_FAULT_SIGBUS;
+
+        ret = block_page_mkwrite(vma, vmf, nilfs_get_block);
+        if (unlikely(ret)) {
+                nilfs_transaction_abort(inode->i_sb);
+                return ret;
+        }
+        nilfs_transaction_commit(inode->i_sb);
+
+ mapped:
         SetPageChecked(page);
         wait_on_page_writeback(page);
         return 0;