ocfs2: Small refactor of truncate zeroing code

We'll want to reuse most of this when pushing inline data back out to an
extent. Keeping this part as a seperate patch helps to keep the upcoming
changes for write support uncluttered.

The core portion of ocfs2_zero_cluster_pages() responsible for making sure a
page is mapped and properly dirtied is abstracted out into it's own
function, ocfs2_map_and_dirty_page(). Actual functionality doesn't change,
though zeroing becomes optional.

We also turn part of ocfs2_free_write_ctxt() into  a common function for
unlocking and freeing a page array. This operation is very common (and
uniform) for Ocfs2 cluster sizes greater than page size, so it makes sense
to keep the code in one place.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Reviewed-by: Joel Becker <joel.becker@oracle.com>

3 files changed, 86 insertions, 87 deletions

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index c91706f949ff..c81bfdfb9929 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -5633,12 +5633,50 @@ static int ocfs2_ordered_zero_func(handle_t *handle, struct buffer_head *bh)
         return ocfs2_journal_dirty_data(handle, bh);
 }
 
+static void ocfs2_map_and_dirty_page(struct inode *inode, handle_t *handle,
+                                     unsigned int from, unsigned int to,
+                                     struct page *page, int zero, u64 *phys)
+{
+        int ret, partial = 0;
+
+        ret = ocfs2_map_page_blocks(page, phys, inode, from, to, 0);
+        if (ret)
+                mlog_errno(ret);
+
+        if (zero)
+                zero_user_page(page, from, to - from, KM_USER0);
+
+        /*
+         * Need to set the buffers we zero'd into uptodate
+         * here if they aren't - ocfs2_map_page_blocks()
+         * might've skipped some
+         */
+        if (ocfs2_should_order_data(inode)) {
+                ret = walk_page_buffers(handle,
+                                        page_buffers(page),
+                                        from, to, &partial,
+                                        ocfs2_ordered_zero_func);
+                if (ret < 0)
+                        mlog_errno(ret);
+        } else {
+                ret = walk_page_buffers(handle, page_buffers(page),
+                                        from, to, &partial,
+                                        ocfs2_writeback_zero_func);
+                if (ret < 0)
+                        mlog_errno(ret);
+        }
+
+        if (!partial)
+                SetPageUptodate(page);
+
+        flush_dcache_page(page);
+}
+
 static void ocfs2_zero_cluster_pages(struct inode *inode, loff_t start,
                                      loff_t end, struct page **pages,
                                      int numpages, u64 phys, handle_t *handle)
 {
-        int i, ret, partial = 0;
-        void *kaddr;
+        int i;
         struct page *page;
         unsigned int from, to = PAGE_CACHE_SIZE;
         struct super_block *sb = inode->i_sb;
@@ -5659,87 +5697,31 @@ static void ocfs2_zero_cluster_pages(struct inode *inode, loff_t start,
                 BUG_ON(from > PAGE_CACHE_SIZE);
                 BUG_ON(to > PAGE_CACHE_SIZE);
 
-                ret = ocfs2_map_page_blocks(page, &phys, inode, from, to, 0);
-                if (ret)
-                        mlog_errno(ret);
-
-                kaddr = kmap_atomic(page, KM_USER0);
-                memset(kaddr + from, 0, to - from);
-                kunmap_atomic(kaddr, KM_USER0);
-
-                /*
-                 * Need to set the buffers we zero'd into uptodate
-                 * here if they aren't - ocfs2_map_page_blocks()
-                 * might've skipped some
-                 */
-                if (ocfs2_should_order_data(inode)) {
-                        ret = walk_page_buffers(handle,
-                                                page_buffers(page),
-                                                from, to, &partial,
-                                                ocfs2_ordered_zero_func);
-                        if (ret < 0)
-                                mlog_errno(ret);
-                } else {
-                        ret = walk_page_buffers(handle, page_buffers(page),
-                                                from, to, &partial,
-                                                ocfs2_writeback_zero_func);
-                        if (ret < 0)
-                                mlog_errno(ret);
-                }
-
-                if (!partial)
-                        SetPageUptodate(page);
-
-                flush_dcache_page(page);
+                ocfs2_map_and_dirty_page(inode, handle, from, to, page, 1,
+                                         &phys);
 
                 start = (page->index + 1) << PAGE_CACHE_SHIFT;
         }
 out:
-        if (pages) {
-                for (i = 0; i < numpages; i++) {
-                        page = pages[i];
-                        unlock_page(page);
-                        mark_page_accessed(page);
-                        page_cache_release(page);
-                }
-        }
+        if (pages)
+                ocfs2_unlock_and_free_pages(pages, numpages);
 }
 
 static int ocfs2_grab_eof_pages(struct inode *inode, loff_t start, loff_t end,
-                                struct page **pages, int *num, u64 *phys)
+                                struct page **pages, int *num)
 {
-        int i, numpages = 0, ret = 0;
-        unsigned int ext_flags;
+        int numpages, ret = 0;
         struct super_block *sb = inode->i_sb;
         struct address_space *mapping = inode->i_mapping;
         unsigned long index;
         loff_t last_page_bytes;
 
-        BUG_ON(!ocfs2_sparse_alloc(OCFS2_SB(sb)));
         BUG_ON(start > end);
 
-        if (start == end)
-                goto out;
-
         BUG_ON(start >> OCFS2_SB(sb)->s_clustersize_bits !=
                (end - 1) >> OCFS2_SB(sb)->s_clustersize_bits);
 
-        ret = ocfs2_extent_map_get_blocks(inode, start >> sb->s_blocksize_bits,
-                                          phys, NULL, &ext_flags);
-        if (ret) {
-                mlog_errno(ret);
-                goto out;
-        }
-
-        /* Tail is a hole. */
-        if (*phys == 0)
-                goto out;
-
-        /* Tail is marked as unwritten, we can count on write to zero
-         * in that case. */
-        if (ext_flags & OCFS2_EXT_UNWRITTEN)
-                goto out;
-
+        numpages = 0;
         last_page_bytes = PAGE_ALIGN(end);
         index = start >> PAGE_CACHE_SHIFT;
         do {
@@ -5756,14 +5738,8 @@ static int ocfs2_grab_eof_pages(struct inode *inode, loff_t start, loff_t end,
 
 out:
         if (ret != 0) {
-                if (pages) {
-                        for (i = 0; i < numpages; i++) {
-                                if (pages[i]) {
-                                        unlock_page(pages[i]);
-                                        page_cache_release(pages[i]);
-                                }
-                        }
-                }
+                if (pages)
+                        ocfs2_unlock_and_free_pages(pages, numpages);
                 numpages = 0;
         }
 
@@ -5784,18 +5760,20 @@ out:
 int ocfs2_zero_range_for_truncate(struct inode *inode, handle_t *handle,
                                   u64 range_start, u64 range_end)
 {
-        int ret, numpages;
+        int ret = 0, numpages;
         struct page **pages = NULL;
         u64 phys;
+        unsigned int ext_flags;
+        struct super_block *sb = inode->i_sb;
 
         /*
          * File systems which don't support sparse files zero on every
          * extend.
          */
-        if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
+        if (!ocfs2_sparse_alloc(OCFS2_SB(sb)))
                 return 0;
 
-        pages = kcalloc(ocfs2_pages_per_cluster(inode->i_sb),
+        pages = kcalloc(ocfs2_pages_per_cluster(sb),
                         sizeof(struct page *), GFP_NOFS);
         if (pages == NULL) {
                 ret = -ENOMEM;
@@ -5803,15 +5781,30 @@ int ocfs2_zero_range_for_truncate(struct inode *inode, handle_t *handle,
                 goto out;
         }
 
-        ret = ocfs2_grab_eof_pages(inode, range_start, range_end, pages,
-                                   &numpages, &phys);
+        if (range_start == range_end)
+                goto out;
+
+        ret = ocfs2_extent_map_get_blocks(inode,
+                                          range_start >> sb->s_blocksize_bits,
+                                          &phys, NULL, &ext_flags);
         if (ret) {
                 mlog_errno(ret);
                 goto out;
         }
 
-        if (numpages == 0)
+        /*
+         * Tail is a hole, or is marked unwritten. In either case, we
+         * can count on read and write to return/push zero's.
+         */
+        if (phys == 0 || ext_flags & OCFS2_EXT_UNWRITTEN)
+                goto out;
+
+        ret = ocfs2_grab_eof_pages(inode, range_start, range_end, pages,
+                                   &numpages);
+        if (ret) {
+                mlog_errno(ret);
                 goto out;
+        }
 
         ocfs2_zero_cluster_pages(inode, range_start, range_end, pages,
                                  numpages, phys, handle);
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index fae07672eb18..8416e383197c 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -830,18 +830,22 @@ struct ocfs2_write_ctxt {
         struct ocfs2_cached_dealloc_ctxt w_dealloc;
 };
 
-static void ocfs2_free_write_ctxt(struct ocfs2_write_ctxt *wc)
+void ocfs2_unlock_and_free_pages(struct page **pages, int num_pages)
 {
         int i;
 
-        for(i = 0; i < wc->w_num_pages; i++) {
-                if (wc->w_pages[i] == NULL)
-                        continue;
-
-                unlock_page(wc->w_pages[i]);
-                mark_page_accessed(wc->w_pages[i]);
-                page_cache_release(wc->w_pages[i]);
+        for(i = 0; i < num_pages; i++) {
+                if (pages[i]) {
+                        unlock_page(pages[i]);
+                        mark_page_accessed(pages[i]);
+                        page_cache_release(pages[i]);
+                }
         }
+}
+
+static void ocfs2_free_write_ctxt(struct ocfs2_write_ctxt *wc)
+{
+        ocfs2_unlock_and_free_pages(wc->w_pages, wc->w_num_pages);
 
         brelse(wc->w_di_bh);
         kfree(wc);
diff --git a/fs/ocfs2/aops.h b/fs/ocfs2/aops.h
index 389579bd64e3..b4fa37d40db4 100644
--- a/fs/ocfs2/aops.h
+++ b/fs/ocfs2/aops.h
@@ -34,6 +34,8 @@ int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno,
                           struct inode *inode, unsigned int from,
                           unsigned int to, int new);
 
+void ocfs2_unlock_and_free_pages(struct page **pages, int num_pages);
+
 int walk_page_buffers(  handle_t *handle,
                         struct buffer_head *head,
                         unsigned from,