These optional file_operations notify a file implementation when it is
installed or uninstalled from a task's fd table. This can be used for
accounting of file-backed shared resources like dma-buf.
This involves some changes to the __fd_install() and __close_fd() APIs
to actually pass along the responsible task_struct. These are low-level
APIs with only two in-tree callers, both adjusted in this patch.
Signed-off-by: Greg Hackmann <ghackm...@google.com>
Signed-off-by: Ruchi Kandoi <kandoiru...@google.com>
---
drivers/android/binder.c | 4 ++--
fs/file.c | 38 +++++++++++++++++++++++++++++---------
fs/open.c | 2 +-
include/linux/fdtable.h | 4 ++--
include/linux/fs.h | 2 ++
5 files changed, 36 insertions(+), 14 deletions(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 562af94..0bb174e 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -398,7 +398,7 @@ static void task_fd_install(
struct binder_proc *proc, unsigned int fd, struct file *file)
{
if (proc->files)
- __fd_install(proc->files, fd, file);
+ __fd_install(proc->tsk, fd, file);
}
/*
@@ -411,7 +411,7 @@ static long task_close_fd(struct binder_proc *proc,
unsigned int fd)
if (proc->files == NULL)
return -ESRCH;
- retval = __close_fd(proc->files, fd);
+ retval = __close_fd(proc->tsk, fd);
/* can't restart close syscall because file table entry was cleared */
if (unlikely(retval == -ERESTARTSYS ||
retval == -ERESTARTNOINTR ||
diff --git a/fs/file.c b/fs/file.c
index 69d6990..19c5fad 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -282,6 +282,24 @@ static unsigned int count_open_files(struct fdtable *fdt)
return i;
}
+static inline void fdt_install(struct fdtable *fdt, int fd, struct file *file,
+ struct task_struct *task)
+{
+ if (file->f_op->installed)
+ file->f_op->installed(file, task);
+ rcu_assign_pointer(fdt->fd[fd], file);
+}
+
+static inline void fdt_uninstall(struct fdtable *fdt, int fd,
+ struct task_struct *task)
+{
+ struct file *old_file = fdt->fd[fd];
+
+ if (old_file->f_op->uninstalled)
+ old_file->f_op->uninstalled(old_file, task);
+ rcu_assign_pointer(fdt->fd[fd], NULL);
+}
+
/*
* Allocate a new files structure and copy contents from the
* passed in files structure.
@@ -543,7 +561,7 @@ int __alloc_fd(struct files_struct *files,
/* Sanity check */
if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
- rcu_assign_pointer(fdt->fd[fd], NULL);
+ fdt_uninstall(fdt, fd, current);
}
#endif
@@ -601,10 +619,11 @@ EXPORT_SYMBOL(put_unused_fd);
* fd_install() instead.
*/
-void __fd_install(struct files_struct *files, unsigned int fd,
+void __fd_install(struct task_struct *task, unsigned int fd,
struct file *file)
{
struct fdtable *fdt;
+ struct files_struct *files = task->files;
might_sleep();
rcu_read_lock_sched();
@@ -618,13 +637,13 @@ void __fd_install(struct files_struct *files, unsigned
int fd,
smp_rmb();
fdt = rcu_dereference_sched(files->fdt);
BUG_ON(fdt->fd[fd] != NULL);
- rcu_assign_pointer(fdt->fd[fd], file);
+ fdt_install(fdt, fd, file, task);
rcu_read_unlock_sched();
}
void fd_install(unsigned int fd, struct file *file)
{
- __fd_install(current->files, fd, file);
+ __fd_install(current, fd, file);
}
EXPORT_SYMBOL(fd_install);
@@ -632,10 +651,11 @@ EXPORT_SYMBOL(fd_install);
/*
* The same warnings as for __alloc_fd()/__fd_install() apply here...
*/
-int __close_fd(struct files_struct *files, unsigned fd)
+int __close_fd(struct task_struct *task, unsigned fd)
{
struct file *file;
struct fdtable *fdt;
+ struct files_struct *files = task->files;
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
@@ -644,7 +664,7 @@ int __close_fd(struct files_struct *files, unsigned fd)
file = fdt->fd[fd];
if (!file)
goto out_unlock;
- rcu_assign_pointer(fdt->fd[fd], NULL);
+ fdt_uninstall(fdt, fd, task);
__clear_close_on_exec(fd, fdt);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
@@ -679,7 +699,7 @@ void do_close_on_exec(struct files_struct *files)
file = fdt->fd[fd];
if (!file)
continue;
- rcu_assign_pointer(fdt->fd[fd], NULL);
+ fdt_uninstall(fdt, fd, current);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
filp_close(file, files);
@@ -846,7 +866,7 @@ __releases(&files->file_lock)
if (!tofree && fd_is_open(fd, fdt))
goto Ebusy;
get_file(file);
- rcu_assign_pointer(fdt->fd[fd], file);
+ fdt_install(fdt, fd, file, current);
__set_open_fd(fd, fdt);
if (flags & O_CLOEXEC)
__set_close_on_exec(fd, fdt);
@@ -870,7 +890,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned
flags)
struct files_struct *files = current->files;
if (!file)
- return __close_fd(files, fd);
+ return __close_fd(current, fd);
if (fd >= rlimit(RLIMIT_NOFILE))
return -EBADF;
diff --git a/fs/open.c b/fs/open.c
index 8aeb08b..0f1db76 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1120,7 +1120,7 @@ EXPORT_SYMBOL(filp_close);
*/
SYSCALL_DEFINE1(close, unsigned int, fd)
{
- int retval = __close_fd(current->files, fd);
+ int retval = __close_fd(current, fd);
/* can't restart close syscall because file table entry was cleared */
if (unlikely(retval == -ERESTARTSYS ||
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index aca2a6a..a45fce3 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -113,9 +113,9 @@ int iterate_fd(struct files_struct *, unsigned,
extern int __alloc_fd(struct files_struct *files,
unsigned start, unsigned end, unsigned flags);
-extern void __fd_install(struct files_struct *files,
+extern void __fd_install(struct task_struct *task,
unsigned int fd, struct file *file);
-extern int __close_fd(struct files_struct *files,
+extern int __close_fd(struct task_struct *task,
unsigned int fd);
extern struct kmem_cache *files_cachep;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c145219..d62bce8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1730,6 +1730,8 @@ struct file_operations {
u64);
ssize_t (*dedupe_file_range)(struct file *, u64, u64, struct file *,
u64);
+ void (*installed)(struct file *file, struct task_struct *task);
+ void (*uninstalled)(struct file *file, struct task_struct *task);
};
struct inode_operations {
--
2.8.0.rc3.226.g39d4020
