[Ocfs2-devel] [PATCH] ocfs2: the ip_alloc_sem should be taken in ocfs2_get_block()

[alex chen <alex.chen@huawei.com>]

The ip_alloc_sem should be taken in ocfs2_get_block() when reading file
in DIRECT mode to prevent concurrent access to extent tree with
ocfs2_dio_end_io_write(), which may cause BUGON in
ocfs2_get_clusters_nocache()->BUG_ON(v_cluster < le32_to_cpu(rec->e_cpos))

Signed-off-by: Alex Chen <alex.chen@huawei.com>
Reviewed-by: Jun Piao <piaojun@huawei.com>

---
 fs/ocfs2/aops.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 88a31e9..5cb939f 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -134,6 +134,19 @@ static int ocfs2_symlink_get_block(struct inode *inode, sector_t iblock,
 	return err;
 }

+static int ocfs2_get_block_lock(struct inode *inode, sector_t iblock,
+		    struct buffer_head *bh_result, int create)
+{
+	int ret;
+	struct ocfs2_inode_info *oi = OCFS2_I(inode);
+
+	down_read(&oi->ip_alloc_sem);
+	ret = ocfs2_get_block(inode, iblock, bh_result, create);
+	up_read(&oi->ip_alloc_sem);
+
+	return ret;
+}
+
 int ocfs2_get_block(struct inode *inode, sector_t iblock,
 		    struct buffer_head *bh_result, int create)
 {
@@ -2154,12 +2167,8 @@ static int ocfs2_dio_get_block(struct inode *inode, sector_t iblock,
 	 * while file size will be changed.
 	 */
 	if (pos + total_len <= i_size_read(inode)) {
-		down_read(&oi->ip_alloc_sem);
 		/* This is the fast path for re-write. */
-		ret = ocfs2_get_block(inode, iblock, bh_result, create);
-
-		up_read(&oi->ip_alloc_sem);
-
+		ret = ocfs2_get_block_lock(inode, iblock, bh_result, create);
 		if (buffer_mapped(bh_result) &&
 		    !buffer_new(bh_result) &&
 		    ret == 0)
@@ -2424,7 +2433,7 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 		return 0;

 	if (iov_iter_rw(iter) == READ)
-		get_block = ocfs2_get_block;
+		get_block = ocfs2_get_block_lock;
 	else
 		get_block = ocfs2_dio_get_block;

-- 1.9.5.msysgit.1