ext4: add a new ioctl EXT4_IOC_CLEAR_ES_CACHE

The new ioctl EXT4_IOC_CLEAR_ES_CACHE will force an inode's extent
status cache to be cleared out.  This is intended for use for
debugging.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

4 files changed, 40 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index bf660aa7a9e0..b22f24f1d365 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -649,6 +649,8 @@ enum {
 #define EXT4_IOC_SET_ENCRYPTION_POLICY  FS_IOC_SET_ENCRYPTION_POLICY
 #define EXT4_IOC_GET_ENCRYPTION_PWSALT  FS_IOC_GET_ENCRYPTION_PWSALT
 #define EXT4_IOC_GET_ENCRYPTION_POLICY  FS_IOC_GET_ENCRYPTION_POLICY
+/* ioctl codes 19--39 are reserved for fscrypt */
+#define EXT4_IOC_CLEAR_ES_CACHE         _IO('f', 40)
 
 #define EXT4_IOC_FSGETXATTR             FS_IOC_FSGETXATTR
 #define EXT4_IOC_FSSETXATTR             FS_IOC_FSSETXATTR
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 7521de2dcf3a..02cc8eb3eb0e 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -1374,6 +1374,34 @@ static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan)
         return nr_shrunk;
 }
 
+/*
+ * Called to support EXT4_IOC_CLEAR_ES_CACHE.  We can only remove
+ * discretionary entries from the extent status cache.  (Some entries
+ * must be present for proper operations.)
+ */
+void ext4_clear_inode_es(struct inode *inode)
+{
+        struct ext4_inode_info *ei = EXT4_I(inode);
+        struct extent_status *es;
+        struct ext4_es_tree *tree;
+        struct rb_node *node;
+
+        write_lock(&ei->i_es_lock);
+        tree = &EXT4_I(inode)->i_es_tree;
+        tree->cache_es = NULL;
+        node = rb_first(&tree->root);
+        while (node) {
+                es = rb_entry(node, struct extent_status, rb_node);
+                node = rb_next(node);
+                if (!ext4_es_is_delayed(es)) {
+                        rb_erase(&es->rb_node, &tree->root);
+                        ext4_es_free_extent(inode, es);
+                }
+        }
+        ext4_clear_inode_state(inode, EXT4_STATE_EXT_PRECACHED);
+        write_unlock(&ei->i_es_lock);
+}
+
 #ifdef ES_DEBUG__
 static void ext4_print_pending_tree(struct inode *inode)
 {
diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
index 131a8b7df265..e16785f431e7 100644
--- a/fs/ext4/extents_status.h
+++ b/fs/ext4/extents_status.h
@@ -248,5 +248,6 @@ extern unsigned int ext4_es_delayed_clu(struct inode *inode, ext4_lblk_t lblk,
                                         ext4_lblk_t len);
 extern void ext4_es_remove_blks(struct inode *inode, ext4_lblk_t lblk,
                                 ext4_lblk_t len);
+extern void ext4_clear_inode_es(struct inode *inode);
 
 #endif /* _EXT4_EXTENTS_STATUS_H */
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 442f7ef873fc..15b1047878ab 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1115,6 +1115,14 @@ resizefs_out:
         case EXT4_IOC_GET_ENCRYPTION_POLICY:
                 return fscrypt_ioctl_get_policy(filp, (void __user *)arg);
 
+        case EXT4_IOC_CLEAR_ES_CACHE:
+        {
+                if (!inode_owner_or_capable(inode))
+                        return -EACCES;
+                ext4_clear_inode_es(inode);
+                return 0;
+        }
+
         case EXT4_IOC_FSGETXATTR:
         {
                 struct fsxattr fa;
@@ -1233,6 +1241,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
         case EXT4_IOC_GET_ENCRYPTION_POLICY:
         case EXT4_IOC_SHUTDOWN:
         case FS_IOC_GETFSMAP:
+        case EXT4_IOC_CLEAR_ES_CACHE:
                 break;
         default:
                 return -ENOIOCTLCMD;