GFS2: directly write blocks past i_size

GFS2 was relying on the writepage code to write out the zeroed data for
fallocate.  However, with FALLOC_FL_KEEP_SIZE set, this may be past i_size.
If it is, it will be ignored.  To work around this, gfs2 now calls
write_dirty_buffer directly on the buffer_heads when FALLOC_FL_KEEP_SIZE
is set, and it's writing past i_size.

This version is just a cleanup of my last version

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 48 insertions, 10 deletions

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index b2682e073eee..e48310885c48 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -617,18 +617,51 @@ static ssize_t gfs2_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
         return generic_file_aio_write(iocb, iov, nr_segs, pos);
 }
 
-static void empty_write_end(struct page *page, unsigned from,
-                           unsigned to)
+static int empty_write_end(struct page *page, unsigned from,
+                           unsigned to, int mode)
 {
-        struct gfs2_inode *ip = GFS2_I(page->mapping->host);
+        struct inode *inode = page->mapping->host;
+        struct gfs2_inode *ip = GFS2_I(inode);
+        struct buffer_head *bh;
+        unsigned offset, blksize = 1 << inode->i_blkbits;
+        pgoff_t end_index = i_size_read(inode) >> PAGE_CACHE_SHIFT;
 
         zero_user(page, from, to-from);
         mark_page_accessed(page);
 
-        if (!gfs2_is_writeback(ip))
-                gfs2_page_add_databufs(ip, page, from, to);
+        if (page->index < end_index || !(mode & FALLOC_FL_KEEP_SIZE)) {
+                if (!gfs2_is_writeback(ip))
+                        gfs2_page_add_databufs(ip, page, from, to);
+
+                block_commit_write(page, from, to);
+                return 0;
+        }
+
+        offset = 0;
+        bh = page_buffers(page);
+        while (offset < to) {
+                if (offset >= from) {
+                        set_buffer_uptodate(bh);
+                        mark_buffer_dirty(bh);
+                        clear_buffer_new(bh);
+                        write_dirty_buffer(bh, WRITE);
+                }
+                offset += blksize;
+                bh = bh->b_this_page;
+        }
 
-        block_commit_write(page, from, to);
+        offset = 0;
+        bh = page_buffers(page);
+        while (offset < to) {
+                if (offset >= from) {
+                        wait_on_buffer(bh);
+                        if (!buffer_uptodate(bh))
+                                return -EIO;
+                }
+                offset += blksize;
+                bh = bh->b_this_page;
+        }
+        return 0;
 }
 
 static int needs_empty_write(sector_t block, struct inode *inode)
@@ -643,7 +676,8 @@ static int needs_empty_write(sector_t block, struct inode *inode)
         return !buffer_mapped(&bh_map);
 }
 
-static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
+static int write_empty_blocks(struct page *page, unsigned from, unsigned to,
+                              int mode)
 {
         struct inode *inode = page->mapping->host;
         unsigned start, end, next, blksize;
@@ -668,7 +702,9 @@ static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
                                                           gfs2_block_map);
                                 if (unlikely(ret))
                                         return ret;
-                                empty_write_end(page, start, end);
+                                ret = empty_write_end(page, start, end, mode);
+                                if (unlikely(ret))
+                                        return ret;
                                 end = 0;
                         }
                         start = next;
@@ -682,7 +718,9 @@ static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
                 ret = __block_write_begin(page, start, end - start, gfs2_block_map);
                 if (unlikely(ret))
                         return ret;
-                empty_write_end(page, start, end);
+                ret = empty_write_end(page, start, end, mode);
+                if (unlikely(ret))
+                        return ret;
         }
 
         return 0;
@@ -731,7 +769,7 @@ static int fallocate_chunk(struct inode *inode, loff_t offset, loff_t len,
 
                 if (curr == end)
                         to = end_offset;
-                error = write_empty_blocks(page, from, to);
+                error = write_empty_blocks(page, from, to, mode);
                 if (!error && offset + to > inode->i_size &&
                     !(mode & FALLOC_FL_KEEP_SIZE)) {
                         i_size_write(inode, offset + to);