[Ocfs2-devel] [PATCH] ocfs2: check the metadate alloc before marking extent written

[alex chen]

We need to check the free number of the records in each loop to mark
extent written, because the last extent block may be changed through
many times marking extent written and the 'num_free_extents' also be
changed. In the worst case, the 'num_free_extents' may become less
than the beginning of the loop. So we should not estimate the free
number of the records at the beginning of the loop to mark extent
written.

Reported-by: John Lightsey <john at nixnuts.net>
Signed-off-by: Alex Chen <alex.chen at huawei.com>
Reviewed-by: Jun Piao <piaojun at huawei.com>
---
 fs/ocfs2/aops.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 64 insertions(+), 12 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index d151632..702aebc 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2272,6 +2272,35 @@ static int ocfs2_dio_wr_get_block(struct inode *inode, sector_t iblock,
 	return ret;
 }

+static int ocfs2_dio_should_restart(struct ocfs2_extent_tree *et,
+		struct ocfs2_alloc_context *meta_ac, int max_rec_needed)
+{
+	int status = 0, free_extents;
+
+	free_extents = ocfs2_num_free_extents(et);
+	if (free_extents < 0) {
+		status = free_extents;
+		mlog_errno(status);
+		return status;
+	}
+
+	/*
+	 * there are two cases which could cause us to EAGAIN in the
+	 * we-need-more-metadata case:
+	 * 1) we haven't reserved *any*
+	 * 2) we are so fragmented, we've needed to add metadata too
+	 *    many times.
+	 */
+	if (free_extents < max_rec_needed) {
+		if (!meta_ac || (ocfs2_alloc_context_bits_left(meta_ac)
+				< ocfs2_extend_meta_needed(et->et_root_el)))
+			status = 1;
+	}
+
+	return status;
+}
+
+#define OCFS2_MAX_REC_NEEDED_SPLIT 2
 static int ocfs2_dio_end_io_write(struct inode *inode,
 				  struct ocfs2_dio_write_ctxt *dwc,
 				  loff_t offset,
@@ -2281,14 +2310,13 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
 	struct ocfs2_extent_tree et;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 	struct ocfs2_inode_info *oi = OCFS2_I(inode);
-	struct ocfs2_unwritten_extent *ue = NULL;
+	struct ocfs2_unwritten_extent *ue = NULL, *tmp_ue;
 	struct buffer_head *di_bh = NULL;
 	struct ocfs2_dinode *di;
-	struct ocfs2_alloc_context *data_ac = NULL;
 	struct ocfs2_alloc_context *meta_ac = NULL;
 	handle_t *handle = NULL;
 	loff_t end = offset + bytes;
-	int ret = 0, credits = 0, locked = 0;
+	int ret = 0, credits = 0, locked = 0, restart = 0;

 	ocfs2_init_dealloc_ctxt(&dealloc);

@@ -2330,8 +2358,9 @@ static int ocfs2_dio_end_io_write(struct inode *inode,

 	ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);

-	ret = ocfs2_lock_allocators(inode, &et, 0, dwc->dw_zero_count*2,
-				    &data_ac, &meta_ac);
+restart_all:
+	ret = ocfs2_lock_allocators(inode, &et, 0, OCFS2_MAX_REC_NEEDED_SPLIT,
+				    NULL, &meta_ac);
 	if (ret) {
 		mlog_errno(ret);
 		goto unlock;
@@ -2343,7 +2372,7 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
 		mlog_errno(ret);
-		goto unlock;
+		goto free_ac;
 	}
 	ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
 				      OCFS2_JOURNAL_ACCESS_WRITE);
@@ -2352,7 +2381,17 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
 		goto commit;
 	}

-	list_for_each_entry(ue, &dwc->dw_zero_list, ue_node) {
+	list_for_each_entry_safe(ue, tmp_ue, &dwc->dw_zero_list, ue_node) {
+		ret = ocfs2_dio_should_restart(&et, meta_ac,
+				OCFS2_MAX_REC_NEEDED_SPLIT * 2);
+		if (ret < 0) {
+			mlog_errno(ret);
+			break;
+		} else if (ret == 1) {
+			restart = 1;
+			break;
+		}
+
 		ret = ocfs2_mark_extent_written(inode, &et, handle,
 						ue->ue_cpos, 1,
 						ue->ue_phys,
@@ -2361,24 +2400,37 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
 			mlog_errno(ret);
 			break;
 		}
+
+		dwc->dw_zero_count--;
+		list_del_init(&ue->ue_node);
+		spin_lock(&oi->ip_lock);
+		list_del_init(&ue->ue_ip_node);
+		spin_unlock(&oi->ip_lock);
+		kfree(ue);
 	}

-	if (end > i_size_read(inode)) {
+	if (!restart && end > i_size_read(inode)) {
 		ret = ocfs2_set_inode_size(handle, inode, di_bh, end);
 		if (ret < 0)
 			mlog_errno(ret);
 	}
+
 commit:
 	ocfs2_commit_trans(osb, handle);
+free_ac:
+	if (meta_ac) {
+		ocfs2_free_alloc_context(meta_ac);
+		meta_ac = NULL;
+	}
+	if (restart) {
+		restart = 0;
+		goto restart_all;
+	}
 unlock:
 	up_write(&oi->ip_alloc_sem);
 	ocfs2_inode_unlock(inode, 1);
 	brelse(di_bh);
 out:
-	if (data_ac)
-		ocfs2_free_alloc_context(data_ac);
-	if (meta_ac)
-		ocfs2_free_alloc_context(meta_ac);
 	ocfs2_run_deallocs(osb, &dealloc);
 	if (locked)
 		inode_unlock(inode);
-- 
1.9.5.msysgit.1