fat: rcu-delay unloading nls and freeing sbi

makes ->d_hash() and ->d_compare() safety in RCU mode independent
from vfsmount_lock.

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

2 files changed, 12 insertions, 8 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 4241e6f39e86..7c31f4bc74a9 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -102,6 +102,7 @@ struct msdos_sb_info {
         struct hlist_head dir_hashtable[FAT_HASH_SIZE];
 
         unsigned int dirty;           /* fs state before mount */
+        struct rcu_head rcu;
 };
 
 #define FAT_CACHE_VALID 0       /* special case for valid cache */
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 0062da21dd8b..854b578f6695 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -548,6 +548,16 @@ static void fat_set_state(struct super_block *sb,
         brelse(bh);
 }
 
+static void delayed_free(struct rcu_head *p)
+{
+        struct msdos_sb_info *sbi = container_of(p, struct msdos_sb_info, rcu);
+        unload_nls(sbi->nls_disk);
+        unload_nls(sbi->nls_io);
+        if (sbi->options.iocharset != fat_default_iocharset)
+                kfree(sbi->options.iocharset);
+        kfree(sbi);
+}
+
 static void fat_put_super(struct super_block *sb)
 {
         struct msdos_sb_info *sbi = MSDOS_SB(sb);
@@ -557,14 +567,7 @@ static void fat_put_super(struct super_block *sb)
         iput(sbi->fsinfo_inode);
         iput(sbi->fat_inode);
 
-        unload_nls(sbi->nls_disk);
-        unload_nls(sbi->nls_io);
-
-        if (sbi->options.iocharset != fat_default_iocharset)
-                kfree(sbi->options.iocharset);
-
-        sb->s_fs_info = NULL;
-        kfree(sbi);
+        call_rcu(&sbi->rcu, delayed_free);
 }
 
 static struct kmem_cache *fat_inode_cachep;