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Commit dcfadfa4 authored by Al Viro's avatar Al Viro
Browse files

new helper: __alloc_fd() 



Essentially, alloc_fd() in a files_struct we own a reference to.
Most of the time wanting to use it is a sign of lousy API
design (such as android/binder).  It's *not* a general-purpose
interface; better that than open-coding its guts, but again,
playing with other process' descriptor table is a sign of bad
design.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent f33ff992

drivers/staging/android/binder.c

+5 −54
Original line number Diff line number Diff line
@@ -362,71 +362,22 @@ struct binder_transaction { 
static void

binder_defer_work(struct binder_proc *proc, enum binder_deferred_state defer);



/*

 * copied from get_unused_fd_flags

 */

int task_get_unused_fd_flags(struct binder_proc *proc, int flags)

{

	struct files_struct *files = proc->files;

	int fd, error;

	struct fdtable *fdt;

	unsigned long rlim_cur;

	unsigned long irqs;



	if (files == NULL)

		return -ESRCH;



	error = -EMFILE;

	spin_lock(&files->file_lock);



repeat:

	fdt = files_fdtable(files);

	fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, files->next_fd);

	if (!lock_task_sighand(proc->tsk, &irqs))

		return -EMFILE;



	/*

	 * N.B. For clone tasks sharing a files structure, this test

	 * will limit the total number of files that can be opened.

	 */

	rlim_cur = 0;

	if (lock_task_sighand(proc->tsk, &irqs)) {

		rlim_cur = proc->tsk->signal->rlim[RLIMIT_NOFILE].rlim_cur;

	rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE);

	unlock_task_sighand(proc->tsk, &irqs);

	}

	if (fd >= rlim_cur)

		goto out;



	/* Do we need to expand the fd array or fd set?  */

	error = expand_files(files, fd);

	if (error < 0)

		goto out;



	if (error) {

		/*

		 * If we needed to expand the fs array we

		 * might have blocked - try again.

		 */

		error = -EMFILE;

		goto repeat;

	}



	__set_open_fd(fd, fdt);

	if (flags & O_CLOEXEC)

		__set_close_on_exec(fd, fdt);

	else

		__clear_close_on_exec(fd, fdt);

	files->next_fd = fd + 1;

#if 1

	/* Sanity check */

	if (fdt->fd[fd] != NULL) {

		pr_warn("get_unused_fd: slot %d not NULL!\n", fd);

		fdt->fd[fd] = NULL;

	}

#endif

	error = fd;



out:

	spin_unlock(&files->file_lock);

	return error;

	return __alloc_fd(files, 0, rlim_cur, flags);

}



/*

fs/file.c

+8 −4
Original line number Diff line number Diff line
@@ -420,11 +420,10 @@ struct files_struct init_files = { 
/*

 * allocate a file descriptor, mark it busy.

 */

int alloc_fd(unsigned start, unsigned flags)

int __alloc_fd(struct files_struct *files,

	       unsigned start, unsigned end, unsigned flags)

{

	struct files_struct *files = current->files;

	unsigned int fd;

	unsigned end = rlimit(RLIMIT_NOFILE);

	int error;

	struct fdtable *fdt;
@@ -479,8 +478,13 @@ out: 
	return error;

}



int alloc_fd(unsigned start, unsigned flags)

{

	return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);

}



int get_unused_fd_flags(unsigned flags)

{

	return alloc_fd(0, flags);

	return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);

}

EXPORT_SYMBOL(get_unused_fd_flags);

include/linux/fdtable.h

+3 −0
Original line number Diff line number Diff line
@@ -125,6 +125,9 @@ void reset_files_struct(struct files_struct *); 
int unshare_files(struct files_struct **);

struct files_struct *dup_fd(struct files_struct *, int *);



extern int __alloc_fd(struct files_struct *files,

		      unsigned start, unsigned end, unsigned flags);



extern struct kmem_cache *files_cachep;



#endif /* __LINUX_FDTABLE_H */