ocfs2: Wrap access of directory allocations with ip_alloc_sem.

OCFS2_I(inode)->ip_alloc_sem is a read-write semaphore protecting
local concurrent access of ocfs2 inodes.  However, ocfs2 directories were
not taking the semaphore while they accessed or modified the allocation
tree.

ocfs2_extend_dir() needs to take the semaphore in a write mode when it
adds to the allocation.  All other directory users get there via
ocfs2_bread(), which takes the semaphore in read mode.

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

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
index 67e6866a2a4f..c441ef1f2bad 100644
--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c
@@ -403,7 +403,7 @@ static int ocfs2_extend_dir(struct ocfs2_super *osb,
                             struct buffer_head **new_de_bh)
 {
         int status = 0;
-        int credits, num_free_extents;
+        int credits, num_free_extents, drop_alloc_sem = 0;
         loff_t dir_i_size;
         struct ocfs2_dinode *fe = (struct ocfs2_dinode *) parent_fe_bh->b_data;
         struct ocfs2_alloc_context *data_ac = NULL;
@@ -452,6 +452,9 @@ static int ocfs2_extend_dir(struct ocfs2_super *osb,
                 credits = OCFS2_SIMPLE_DIR_EXTEND_CREDITS;
         }
 
+        down_write(&OCFS2_I(dir)->ip_alloc_sem);
+        drop_alloc_sem = 1;
+
         handle = ocfs2_start_trans(osb, credits);
         if (IS_ERR(handle)) {
                 status = PTR_ERR(handle);
@@ -497,6 +500,8 @@ static int ocfs2_extend_dir(struct ocfs2_super *osb,
         *new_de_bh = new_bh;
         get_bh(*new_de_bh);
 bail:
+        if (drop_alloc_sem)
+                up_write(&OCFS2_I(dir)->ip_alloc_sem);
         if (handle)
                 ocfs2_commit_trans(osb, handle);