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 ghackmann@google.com Signed-off-by: Ruchi Kandoi kandoiruchi@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 {