hfsplus: switch to ->iterate_shared()

We need to protect the list of hfsplus_readdir_data against parallel
insertions (in readdir) and removals (in release).  Add a spinlock
for that.  Note that it has nothing to do with protection of
hfsplus_readdir_data->key - we have an exclusion between hfsplus_readdir()
and hfsplus_delete_cat() on directory lock and between several
hfsplus_readdir() for the same struct file on ->f_pos_lock.  The spinlock
is strictly for list changes.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

5 files changed, 15 insertions, 3 deletions

diff --git a/fs/hfsplus/catalog.c b/fs/hfsplus/catalog.c
index 022974ab6e3c..fb707e8f423a 100644
--- a/fs/hfsplus/catalog.c
+++ b/fs/hfsplus/catalog.c
@@ -374,12 +374,15 @@ int hfsplus_delete_cat(u32 cnid, struct inode *dir, struct qstr *str)
                 hfsplus_free_fork(sb, cnid, &fork, HFSPLUS_TYPE_RSRC);
         }
 
+        /* we only need to take spinlock for exclusion with ->release() */
+        spin_lock(&HFSPLUS_I(dir)->open_dir_lock);
         list_for_each(pos, &HFSPLUS_I(dir)->open_dir_list) {
                 struct hfsplus_readdir_data *rd =
                         list_entry(pos, struct hfsplus_readdir_data, list);
                 if (fd.tree->keycmp(fd.search_key, (void *)&rd->key) < 0)
                         rd->file->f_pos--;
         }
+        spin_unlock(&HFSPLUS_I(dir)->open_dir_lock);
 
         err = hfs_brec_remove(&fd);
         if (err)
diff --git a/fs/hfsplus/dir.c b/fs/hfsplus/dir.c
index a4e867e08947..42e128661dc1 100644
--- a/fs/hfsplus/dir.c
+++ b/fs/hfsplus/dir.c
@@ -271,8 +271,14 @@ next:
                 }
                 file->private_data = rd;
                 rd->file = file;
+                spin_lock(&HFSPLUS_I(inode)->open_dir_lock);
                 list_add(&rd->list, &HFSPLUS_I(inode)->open_dir_list);
+                spin_unlock(&HFSPLUS_I(inode)->open_dir_lock);
         }
+        /*
+         * Can be done after the list insertion; exclusion with
+         * hfsplus_delete_cat() is provided by directory lock.
+         */
         memcpy(&rd->key, fd.key, sizeof(struct hfsplus_cat_key));
 out:
         kfree(strbuf);
@@ -284,9 +290,9 @@ static int hfsplus_dir_release(struct inode *inode, struct file *file)
 {
         struct hfsplus_readdir_data *rd = file->private_data;
         if (rd) {
-                inode_lock(inode);
+                spin_lock(&HFSPLUS_I(inode)->open_dir_lock);
                 list_del(&rd->list);
-                inode_unlock(inode);
+                spin_unlock(&HFSPLUS_I(inode)->open_dir_lock);
                 kfree(rd);
         }
         return 0;
@@ -569,7 +575,7 @@ const struct inode_operations hfsplus_dir_inode_operations = {
 const struct file_operations hfsplus_dir_operations = {
         .fsync          = hfsplus_file_fsync,
         .read           = generic_read_dir,
-        .iterate        = hfsplus_readdir,
+        .iterate_shared = hfsplus_readdir,
         .unlocked_ioctl = hfsplus_ioctl,
         .llseek         = generic_file_llseek,
         .release        = hfsplus_dir_release,
diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
index f91a1faf819e..fdc3446d934a 100644
--- a/fs/hfsplus/hfsplus_fs.h
+++ b/fs/hfsplus/hfsplus_fs.h
@@ -244,6 +244,7 @@ struct hfsplus_inode_info {
         u8 userflags;           /* BSD user file flags */
         u32 subfolders;         /* Subfolder count (HFSX only) */
         struct list_head open_dir_list;
+        spinlock_t open_dir_lock;
         loff_t phys_size;
 
         struct inode vfs_inode;
diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
index b28f39865c3a..037f738c5871 100644
--- a/fs/hfsplus/inode.c
+++ b/fs/hfsplus/inode.c
@@ -374,6 +374,7 @@ struct inode *hfsplus_new_inode(struct super_block *sb, umode_t mode)
 
         hip = HFSPLUS_I(inode);
         INIT_LIST_HEAD(&hip->open_dir_list);
+        spin_lock_init(&hip->open_dir_lock);
         mutex_init(&hip->extents_lock);
         atomic_set(&hip->opencnt, 0);
         hip->extent_state = 0;
diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index c35911362ff9..755bf30ba1ce 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -67,6 +67,7 @@ struct inode *hfsplus_iget(struct super_block *sb, unsigned long ino)
                 return inode;
 
         INIT_LIST_HEAD(&HFSPLUS_I(inode)->open_dir_list);
+        spin_lock_init(&HFSPLUS_I(inode)->open_dir_lock);
         mutex_init(&HFSPLUS_I(inode)->extents_lock);
         HFSPLUS_I(inode)->flags = 0;
         HFSPLUS_I(inode)->extent_state = 0;