HPFS: Introduce a global mutex and lock it on every callback from VFS.

Introduce a global mutex and lock it on every callback from VFS.

Performance doesn't matter, reviewing the whole code for locking correctness
would be too complicated, so simply lock it all.

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 51 insertions, 18 deletions

diff --git a/fs/hpfs/buffer.c b/fs/hpfs/buffer.c
index 793cb9d943d2..7cef5d5c3608 100644
--- a/fs/hpfs/buffer.c
+++ b/fs/hpfs/buffer.c
@@ -32,6 +32,8 @@ void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head
 {
         struct buffer_head *bh;
 
+        hpfs_lock_assert(s);
+
         cond_resched();
 
         *bhp = bh = sb_bread(s, secno);
@@ -50,6 +52,8 @@ void *hpfs_get_sector(struct super_block *s, unsigned secno, struct buffer_head
         struct buffer_head *bh;
         /*return hpfs_map_sector(s, secno, bhp, 0);*/
 
+        hpfs_lock_assert(s);
+
         cond_resched();
 
         if ((*bhp = bh = sb_getblk(s, secno)) != NULL) {
@@ -70,6 +74,8 @@ void *hpfs_map_4sectors(struct super_block *s, unsigned secno, struct quad_buffe
         struct buffer_head *bh;
         char *data;
 
+        hpfs_lock_assert(s);
+
         cond_resched();
 
         if (secno & 3) {
@@ -125,6 +131,8 @@ void *hpfs_get_4sectors(struct super_block *s, unsigned secno,
 {
         cond_resched();
 
+        hpfs_lock_assert(s);
+
         if (secno & 3) {
                 printk("HPFS: hpfs_get_4sectors: unaligned read\n");
                 return NULL;
diff --git a/fs/hpfs/file.c b/fs/hpfs/file.c
index 9b9eb6933e43..09a642f853e1 100644
--- a/fs/hpfs/file.c
+++ b/fs/hpfs/file.c
@@ -48,38 +48,46 @@ static secno hpfs_bmap(struct inode *inode, unsigned file_secno)
 static void hpfs_truncate(struct inode *i)
 {
         if (IS_IMMUTABLE(i)) return /*-EPERM*/;
-        hpfs_lock(i->i_sb);
+        hpfs_lock_assert(i->i_sb);
+
         hpfs_i(i)->i_n_secs = 0;
         i->i_blocks = 1 + ((i->i_size + 511) >> 9);
         hpfs_i(i)->mmu_private = i->i_size;
         hpfs_truncate_btree(i->i_sb, i->i_ino, 1, ((i->i_size + 511) >> 9));
         hpfs_write_inode(i);
         hpfs_i(i)->i_n_secs = 0;
-        hpfs_unlock(i->i_sb);
 }
 
 static int hpfs_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
 {
+        int r;
         secno s;
+        hpfs_lock(inode->i_sb);
         s = hpfs_bmap(inode, iblock);
         if (s) {
                 map_bh(bh_result, inode->i_sb, s);
-                return 0;
+                goto ret_0;
         }
-        if (!create) return 0;
+        if (!create) goto ret_0;
         if (iblock<<9 != hpfs_i(inode)->mmu_private) {
                 BUG();
-                return -EIO;
+                r = -EIO;
+                goto ret_r;
         }
         if ((s = hpfs_add_sector_to_btree(inode->i_sb, inode->i_ino, 1, inode->i_blocks - 1)) == -1) {
                 hpfs_truncate_btree(inode->i_sb, inode->i_ino, 1, inode->i_blocks - 1);
-                return -ENOSPC;
+                r = -ENOSPC;
+                goto ret_r;
         }
         inode->i_blocks++;
         hpfs_i(inode)->mmu_private += 512;
         set_buffer_new(bh_result);
         map_bh(bh_result, inode->i_sb, s);
-        return 0;
+        ret_0:
+        r = 0;
+        ret_r:
+        hpfs_unlock(inode->i_sb);
+        return r;
 }
 
 static int hpfs_writepage(struct page *page, struct writeback_control *wbc)
@@ -130,8 +138,11 @@ static ssize_t hpfs_file_write(struct file *file, const char __user *buf,
         ssize_t retval;
 
         retval = do_sync_write(file, buf, count, ppos);
-        if (retval > 0)
+        if (retval > 0) {
+                hpfs_lock(file->f_path.dentry->d_sb);
                 hpfs_i(file->f_path.dentry->d_inode)->i_dirty = 1;
+                hpfs_unlock(file->f_path.dentry->d_sb);
+        }
         return retval;
 }
 
diff --git a/fs/hpfs/hpfs_fn.h b/fs/hpfs/hpfs_fn.h
index c15adbca07ff..89a4714b44c7 100644
--- a/fs/hpfs/hpfs_fn.h
+++ b/fs/hpfs/hpfs_fn.h
@@ -63,6 +63,7 @@ struct hpfs_inode_info {
 };
 
 struct hpfs_sb_info {
+        struct mutex hpfs_mutex;        /* global hpfs lock */
         ino_t sb_root;                  /* inode number of root dir */
         unsigned sb_fs_size;            /* file system size, sectors */
         unsigned sb_bitmaps;            /* sector number of bitmap list */
@@ -346,21 +347,26 @@ static inline time32_t gmt_to_local(struct super_block *s, time_t t)
 /*
  * Locking:
  *
- * hpfs_lock() is a leftover from the big kernel lock.
- * Right now, these functions are empty and only left
- * for documentation purposes. The file system no longer
- * works on SMP systems, so the lock is not needed
- * any more.
+ * hpfs_lock() locks the whole filesystem. It must be taken
+ * on any method called by the VFS.
  *
- * If someone is interested in making it work again, this
- * would be the place to start by adding a per-superblock
- * mutex and fixing all the bugs and performance issues
- * caused by that.
+ * We don't do any per-file locking anymore, it is hard to
+ * review and HPFS is not performance-sensitive anyway.
  */
 static inline void hpfs_lock(struct super_block *s)
 {
+        struct hpfs_sb_info *sbi = hpfs_sb(s);
+        mutex_lock(&sbi->hpfs_mutex);
 }
 
 static inline void hpfs_unlock(struct super_block *s)
 {
+        struct hpfs_sb_info *sbi = hpfs_sb(s);
+        mutex_unlock(&sbi->hpfs_mutex);
+}
+
+static inline void hpfs_lock_assert(struct super_block *s)
+{
+        struct hpfs_sb_info *sbi = hpfs_sb(s);
+        WARN_ON(!mutex_is_locked(&sbi->hpfs_mutex));
 }
diff --git a/fs/hpfs/super.c b/fs/hpfs/super.c
index 501ea86e40a4..41232c2d60dc 100644
--- a/fs/hpfs/super.c
+++ b/fs/hpfs/super.c
@@ -102,9 +102,12 @@ static void hpfs_put_super(struct super_block *s)
 {
         struct hpfs_sb_info *sbi = hpfs_sb(s);
 
+        hpfs_lock(s);
+        unmark_dirty(s);
+        hpfs_unlock(s);
+
         kfree(sbi->sb_cp_table);
         kfree(sbi->sb_bmp_dir);
-        unmark_dirty(s);
         s->s_fs_info = NULL;
         kfree(sbi);
 }
@@ -490,6 +493,9 @@ static int hpfs_fill_super(struct super_block *s, void *options, int silent)
         sbi->sb_bmp_dir = NULL;
         sbi->sb_cp_table = NULL;
 
+        mutex_init(&sbi->hpfs_mutex);
+        hpfs_lock(s);
+
         mutex_init(&sbi->hpfs_creation_de);
 
         uid = current_uid();
@@ -669,6 +675,7 @@ static int hpfs_fill_super(struct super_block *s, void *options, int silent)
                         root->i_blocks = 5;
                 hpfs_brelse4(&qbh);
         }
+        hpfs_unlock(s);
         return 0;
 
 bail4:  brelse(bh2);
@@ -676,6 +683,7 @@ bail3:	brelse(bh1);
 bail2:  brelse(bh0);
 bail1:
 bail0:
+        hpfs_unlock(s);
         kfree(sbi->sb_bmp_dir);
         kfree(sbi->sb_cp_table);
         s->s_fs_info = NULL;