ocfs2: When zero extending, do it by page.

ocfs2_zero_extend() does its zeroing block by block, but it calls a
function named ocfs2_write_zero_page().  Let's have
ocfs2_write_zero_page() handle the page level.  From
ocfs2_zero_extend()'s perspective, it is now page-at-a-time.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Cc: stable@kernel.org

2 files changed, 84 insertions, 64 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 3623ca20cc18..9a5c931439bd 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -459,36 +459,6 @@ int walk_page_buffers(	handle_t *handle,
         return ret;
 }
 
-handle_t *ocfs2_start_walk_page_trans(struct inode *inode,
-                                                         struct page *page,
-                                                         unsigned from,
-                                                         unsigned to)
-{
-        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
-        handle_t *handle;
-        int ret = 0;
-
-        handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
-        if (IS_ERR(handle)) {
-                ret = -ENOMEM;
-                mlog_errno(ret);
-                goto out;
-        }
-
-        if (ocfs2_should_order_data(inode)) {
-                ret = ocfs2_jbd2_file_inode(handle, inode);
-                if (ret < 0)
-                        mlog_errno(ret);
-        }
-out:
-        if (ret) {
-                if (!IS_ERR(handle))
-                        ocfs2_commit_trans(osb, handle);
-                handle = ERR_PTR(ret);
-        }
-        return handle;
-}
-
 static sector_t ocfs2_bmap(struct address_space *mapping, sector_t block)
 {
         sector_t status;
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 6a13ea64c447..4cfc976a9067 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -724,28 +724,55 @@ leave:
         return status;
 }
 
+/*
+ * While a write will already be ordering the data, a truncate will not.
+ * Thus, we need to explicitly order the zeroed pages.
+ */
+static handle_t *ocfs2_zero_start_ordered_transaction(struct inode *inode)
+{
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        handle_t *handle = NULL;
+        int ret = 0;
+
+        if (!ocfs2_should_order_data(inode))
+                goto out;
+
+        handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
+        if (IS_ERR(handle)) {
+                ret = -ENOMEM;
+                mlog_errno(ret);
+                goto out;
+        }
+
+        ret = ocfs2_jbd2_file_inode(handle, inode);
+        if (ret < 0)
+                mlog_errno(ret);
+
+out:
+        if (ret) {
+                if (!IS_ERR(handle))
+                        ocfs2_commit_trans(osb, handle);
+                handle = ERR_PTR(ret);
+        }
+        return handle;
+}
+
 /* Some parts of this taken from generic_cont_expand, which turned out
  * to be too fragile to do exactly what we need without us having to
  * worry about recursive locking in ->write_begin() and ->write_end(). */
-static int ocfs2_write_zero_page(struct inode *inode,
-                                 u64 size)
+static int ocfs2_write_zero_page(struct inode *inode, u64 abs_from,
+                                 u64 abs_to)
 {
         struct address_space *mapping = inode->i_mapping;
         struct page *page;
-        unsigned long index;
-        unsigned int offset;
+        unsigned long index = abs_from >> PAGE_CACHE_SHIFT;
         handle_t *handle = NULL;
         int ret;
+        unsigned zero_from, zero_to, block_start, block_end;
 
-        offset = (size & (PAGE_CACHE_SIZE-1)); /* Within page */
-        /* ugh.  in prepare/commit_write, if from==to==start of block, we
-        ** skip the prepare.  make sure we never send an offset for the start
-        ** of a block
-        */
-        if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
-                offset++;
-        }
-        index = size >> PAGE_CACHE_SHIFT;
+        BUG_ON(abs_from >= abs_to);
+        BUG_ON(abs_to > (((u64)index + 1) << PAGE_CACHE_SHIFT));
+        BUG_ON(abs_from & (inode->i_blkbits - 1));
 
         page = grab_cache_page(mapping, index);
         if (!page) {
@@ -754,31 +781,51 @@ static int ocfs2_write_zero_page(struct inode *inode,
                 goto out;
         }
 
-        ret = ocfs2_prepare_write_nolock(inode, page, offset, offset);
-        if (ret < 0) {
-                mlog_errno(ret);
-                goto out_unlock;
-        }
+        /* Get the offsets within the page that we want to zero */
+        zero_from = abs_from & (PAGE_CACHE_SIZE - 1);
+        zero_to = abs_to & (PAGE_CACHE_SIZE - 1);
+        if (!zero_to)
+                zero_to = PAGE_CACHE_SIZE;
 
-        if (ocfs2_should_order_data(inode)) {
-                handle = ocfs2_start_walk_page_trans(inode, page, offset,
-                                                     offset);
-                if (IS_ERR(handle)) {
-                        ret = PTR_ERR(handle);
-                        handle = NULL;
+        /* We know that zero_from is block aligned */
+        for (block_start = zero_from; block_start < zero_to;
+             block_start = block_end) {
+                block_end = block_start + (1 << inode->i_blkbits);
+
+                /*
+                 * block_start is block-aligned.  Bump it by one to
+                 * force ocfs2_{prepare,commit}_write() to zero the
+                 * whole block.
+                 */
+                ret = ocfs2_prepare_write_nolock(inode, page,
+                                                 block_start + 1,
+                                                 block_start + 1);
+                if (ret < 0) {
+                        mlog_errno(ret);
                         goto out_unlock;
                 }
-        }
 
-        /* must not update i_size! */
-        ret = block_commit_write(page, offset, offset);
-        if (ret < 0)
-                mlog_errno(ret);
-        else
-                ret = 0;
+                if (!handle) {
+                        handle = ocfs2_zero_start_ordered_transaction(inode);
+                        if (IS_ERR(handle)) {
+                                ret = PTR_ERR(handle);
+                                handle = NULL;
+                                break;
+                        }
+                }
+
+                /* must not update i_size! */
+                ret = block_commit_write(page, block_start + 1,
+                                         block_start + 1);
+                if (ret < 0)
+                        mlog_errno(ret);
+                else
+                        ret = 0;
+        }
 
         if (handle)
                 ocfs2_commit_trans(OCFS2_SB(inode->i_sb), handle);
+
 out_unlock:
         unlock_page(page);
         page_cache_release(page);
@@ -790,18 +837,21 @@ static int ocfs2_zero_extend(struct inode *inode,
                              u64 zero_to_size)
 {
         int ret = 0;
-        u64 start_off;
+        u64 start_off, next_off;
         struct super_block *sb = inode->i_sb;
 
         start_off = ocfs2_align_bytes_to_blocks(sb, i_size_read(inode));
         while (start_off < zero_to_size) {
-                ret = ocfs2_write_zero_page(inode, start_off);
+                next_off = (start_off & PAGE_CACHE_MASK) + PAGE_CACHE_SIZE;
+                if (next_off > zero_to_size)
+                        next_off = zero_to_size;
+                ret = ocfs2_write_zero_page(inode, start_off, next_off);
                 if (ret < 0) {
                         mlog_errno(ret);
                         goto out;
                 }
 
-                start_off += sb->s_blocksize;
+                start_off = next_off;
 
                 /*
                  * Very large extends have the potential to lock up