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Commit ce08b62d authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Al Viro
Browse files

change close_files() to use rcu_dereference_raw(files->fdt) 



put_files_struct() and close_files() do rcu_read_lock() to make
rcu_dereference_check_fdtable() happy.

This looks a bit ugly, files_fdtable() just reads the pointer,
we can simply use rcu_dereference_raw() to avoid the warning.

The patch also changes close_files() to return fdt, this avoids
another rcu_read_lock()/files_fdtable() in put_files_struct().

I think close_files() needs more cleanups:

	- we do not need xchg() exactly because we are the last
	  user of this files_struct

	- "if (file)" should be turned into WARN_ON(!file)

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent a8d4b834

fs/file.c

+9 −17
Original line number Original line Diff line number Diff line
@@ -348,21 +348,16 @@ out: 
	return NULL;

	return NULL;

}

}





static void close_files(struct files_struct * files)

static struct fdtable *close_files(struct files_struct * files)

{

{

	int i, j;

	struct fdtable *fdt;



	j = 0;



	/*

	/*

	 * It is safe to dereference the fd table without RCU or

	 * It is safe to dereference the fd table without RCU or

	 * ->file_lock because this is the last reference to the

	 * ->file_lock because this is the last reference to the

	 * files structure.  But use RCU to shut RCU-lockdep up.

	 * files structure.

	 */

	 */

	rcu_read_lock();

	struct fdtable *fdt = rcu_dereference_raw(files->fdt);

	fdt = files_fdtable(files);

	int i, j = 0;

	rcu_read_unlock();



	for (;;) {

	for (;;) {

		unsigned long set;

		unsigned long set;

		i = j * BITS_PER_LONG;

		i = j * BITS_PER_LONG;
@@ -381,6 +376,8 @@ static void close_files(struct files_struct * files) 
			set >>= 1;

			set >>= 1;

		}

		}

	}

	}



	return fdt;

}

}





struct files_struct *get_files_struct(struct task_struct *task)

struct files_struct *get_files_struct(struct task_struct *task)
@@ -398,14 +395,9 @@ struct files_struct *get_files_struct(struct task_struct *task) 




void put_files_struct(struct files_struct *files)

void put_files_struct(struct files_struct *files)

{

{

	struct fdtable *fdt;



	if (atomic_dec_and_test(&files->count)) {

	if (atomic_dec_and_test(&files->count)) {

		close_files(files);

		struct fdtable *fdt = close_files(files);

		/* not really needed, since nobody can see us */



		rcu_read_lock();

		fdt = files_fdtable(files);

		rcu_read_unlock();

		/* free the arrays if they are not embedded */

		/* free the arrays if they are not embedded */

		if (fdt != &files->fdtab)

		if (fdt != &files->fdtab)

			__free_fdtable(fdt);

			__free_fdtable(fdt);