STAGING: Octeon: Use common helpers for determining interface and port

[linux-drm-fsl-dcu.git] / fs / file.c

diff --git a/fs/file.c b/fs/file.c
index 93c5f89c248b07b6fba50fd31f4bd36ba9520fef..6c672ad329e9a8c6bf3b7925f9e344ea1c5991c4 100644 (file)
--- a/fs/file.c
+++ b/fs/file.c
@@ -147,6 +147,13 @@ static int expand_fdtable(struct files_struct *files, int nr)
 
        spin_unlock(&files->file_lock);
        new_fdt = alloc_fdtable(nr);
+
+       /* make sure all __fd_install() have seen resize_in_progress
+        * or have finished their rcu_read_lock_sched() section.
+        */
+       if (atomic_read(&files->count) > 1)
+               synchronize_sched();
+
        spin_lock(&files->file_lock);
        if (!new_fdt)
                return -ENOMEM;
@@ -158,21 +165,14 @@ static int expand_fdtable(struct files_struct *files, int nr)
                __free_fdtable(new_fdt);
                return -EMFILE;
        }
-       /*
-        * Check again since another task may have expanded the fd table while
-        * we dropped the lock
-        */
        cur_fdt = files_fdtable(files);
-       if (nr >= cur_fdt->max_fds) {
-               /* Continue as planned */
-               copy_fdtable(new_fdt, cur_fdt);
-               rcu_assign_pointer(files->fdt, new_fdt);
-               if (cur_fdt != &files->fdtab)
-                       call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
-       } else {
-               /* Somebody else expanded, so undo our attempt */
-               __free_fdtable(new_fdt);
-       }
+       BUG_ON(nr < cur_fdt->max_fds);
+       copy_fdtable(new_fdt, cur_fdt);
+       rcu_assign_pointer(files->fdt, new_fdt);
+       if (cur_fdt != &files->fdtab)
+               call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
+       /* coupled with smp_rmb() in __fd_install() */
+       smp_wmb();
        return 1;
 }
 
@@ -185,21 +185,38 @@ static int expand_fdtable(struct files_struct *files, int nr)
  * The files->file_lock should be held on entry, and will be held on exit.
  */
 static int expand_files(struct files_struct *files, int nr)
+       __releases(files->file_lock)
+       __acquires(files->file_lock)
 {
        struct fdtable *fdt;
+       int expanded = 0;
 
+repeat:
        fdt = files_fdtable(files);
 
        /* Do we need to expand? */
        if (nr < fdt->max_fds)
-               return 0;
+               return expanded;
 
        /* Can we expand? */
        if (nr >= sysctl_nr_open)
                return -EMFILE;
 
+       if (unlikely(files->resize_in_progress)) {
+               spin_unlock(&files->file_lock);
+               expanded = 1;
+               wait_event(files->resize_wait, !files->resize_in_progress);
+               spin_lock(&files->file_lock);
+               goto repeat;
+       }
+
        /* All good, so we try */
-       return expand_fdtable(files, nr);
+       files->resize_in_progress = true;
+       expanded = expand_fdtable(files, nr);
+       files->resize_in_progress = false;
+
+       wake_up_all(&files->resize_wait);
+       return expanded;
 }
 
 static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
@@ -256,6 +273,8 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
        atomic_set(&newf->count, 1);
 
        spin_lock_init(&newf->file_lock);
+       newf->resize_in_progress = false;
+       init_waitqueue_head(&newf->resize_wait);
        newf->next_fd = 0;
        new_fdt = &newf->fdtab;
        new_fdt->max_fds = NR_OPEN_DEFAULT;
@@ -553,11 +572,21 @@ void __fd_install(struct files_struct *files, unsigned int fd,
                struct file *file)
 {
        struct fdtable *fdt;
-       spin_lock(&files->file_lock);
-       fdt = files_fdtable(files);
+
+       might_sleep();
+       rcu_read_lock_sched();
+
+       while (unlikely(files->resize_in_progress)) {
+               rcu_read_unlock_sched();
+               wait_event(files->resize_wait, !files->resize_in_progress);
+               rcu_read_lock_sched();
+       }
+       /* coupled with smp_wmb() in expand_fdtable() */
+       smp_rmb();
+       fdt = rcu_dereference_sched(files->fdt);
        BUG_ON(fdt->fd[fd] != NULL);
        rcu_assign_pointer(fdt->fd[fd], file);
-       spin_unlock(&files->file_lock);
+       rcu_read_unlock_sched();
 }
 
 void fd_install(unsigned int fd, struct file *file)
@@ -635,11 +664,17 @@ static struct file *__fget(unsigned int fd, fmode_t mask)
        struct file *file;
 
        rcu_read_lock();
+loop:
        file = fcheck_files(files, fd);
        if (file) {
-               /* File object ref couldn't be taken */
-               if ((file->f_mode & mask) || !get_file_rcu(file))
+               /* File object ref couldn't be taken.
+                * dup2() atomicity guarantee is the reason
+                * we loop to catch the new file (or NULL pointer)
+                */
+               if (file->f_mode & mask)
                        file = NULL;
+               else if (!get_file_rcu(file))
+                       goto loop;
        }
        rcu_read_unlock();