1 files changed, 63 insertions, 108 deletions

diff --git a/fs/file_table.c b/fs/file_table.c
index a305d9e2d1b..de9e9653d61 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -23,6 +23,8 @@
 #include <linux/lglock.h>
 #include <linux/percpu_counter.h>
 #include <linux/percpu.h>
+#include <linux/hardirq.h>
+#include <linux/task_work.h>
 #include <linux/ima.h>
 
 #include <linux/atomic.h>
@@ -34,14 +36,14 @@ struct files_stat_struct files_stat = {
 	.max_files = NR_FILE
 };
 
-DEFINE_LGLOCK(files_lglock);
+DEFINE_STATIC_LGLOCK(files_lglock);
 
 /* SLAB cache for file structures */
 static struct kmem_cache *filp_cachep __read_mostly;
 
 static struct percpu_counter nr_files __cacheline_aligned_in_smp;
 
-static inline void file_free_rcu(struct rcu_head *head)
+static void file_free_rcu(struct rcu_head *head)
 {
 	struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
 
@@ -215,7 +217,7 @@ static void drop_file_write_access(struct file *file)
 		return;
 	if (file_check_writeable(file) != 0)
 		return;
-	mnt_drop_write(mnt);
+	__mnt_drop_write(mnt);
 	file_release_write(file);
 }
 
@@ -241,17 +243,16 @@ static void __fput(struct file *file)
 		if (file->f_op && file->f_op->fasync)
 			file->f_op->fasync(-1, file, 0);
 	}
+	ima_file_free(file);
 	if (file->f_op && file->f_op->release)
 		file->f_op->release(inode, file);
 	security_file_free(file);
-	ima_file_free(file);
 	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
 		     !(file->f_mode & FMODE_PATH))) {
 		cdev_put(inode->i_cdev);
 	}
 	fops_put(file->f_op);
 	put_pid(file->f_owner.pid);
-	file_sb_list_del(file);
 	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 		i_readcount_dec(inode);
 	if (file->f_mode & FMODE_WRITE)
@@ -263,120 +264,81 @@ static void __fput(struct file *file)
 	mntput(mnt);
 }
 
-void fput(struct file *file)
+static DEFINE_SPINLOCK(delayed_fput_lock);
+static LIST_HEAD(delayed_fput_list);
+static void delayed_fput(struct work_struct *unused)
 {
-	if (atomic_long_dec_and_test(&file->f_count))
-		__fput(file);
+	LIST_HEAD(head);
+	spin_lock_irq(&delayed_fput_lock);
+	list_splice_init(&delayed_fput_list, &head);
+	spin_unlock_irq(&delayed_fput_lock);
+	while (!list_empty(&head)) {
+		struct file *f = list_first_entry(&head, struct file, f_u.fu_list);
+		list_del_init(&f->f_u.fu_list);
+		__fput(f);
+	}
 }
 
-EXPORT_SYMBOL(fput);
-
-struct file *fget(unsigned int fd)
+static void ____fput(struct callback_head *work)
 {
-	struct file *file;
-	struct files_struct *files = current->files;
-
-	rcu_read_lock();
-	file = fcheck_files(files, fd);
-	if (file) {
-		/* File object ref couldn't be taken */
-		if (file->f_mode & FMODE_PATH ||
-		    !atomic_long_inc_not_zero(&file->f_count))
-			file = NULL;
-	}
-	rcu_read_unlock();
-
-	return file;
+	__fput(container_of(work, struct file, f_u.fu_rcuhead));
 }
 
-EXPORT_SYMBOL(fget);
-
-struct file *fget_raw(unsigned int fd)
+/*
+ * If kernel thread really needs to have the final fput() it has done
+ * to complete, call this.  The only user right now is the boot - we
+ * *do* need to make sure our writes to binaries on initramfs has
+ * not left us with opened struct file waiting for __fput() - execve()
+ * won't work without that.  Please, don't add more callers without
+ * very good reasons; in particular, never call that with locks
+ * held and never call that from a thread that might need to do
+ * some work on any kind of umount.
+ */
+void flush_delayed_fput(void)
 {
-	struct file *file;
-	struct files_struct *files = current->files;
-
-	rcu_read_lock();
-	file = fcheck_files(files, fd);
-	if (file) {
-		/* File object ref couldn't be taken */
-		if (!atomic_long_inc_not_zero(&file->f_count))
-			file = NULL;
-	}
-	rcu_read_unlock();
-
-	return file;
+	delayed_fput(NULL);
 }
 
-EXPORT_SYMBOL(fget_raw);
+static DECLARE_WORK(delayed_fput_work, delayed_fput);
 
-/*
- * Lightweight file lookup - no refcnt increment if fd table isn't shared.
- *
- * You can use this instead of fget if you satisfy all of the following
- * conditions:
- * 1) You must call fput_light before exiting the syscall and returning control
- *    to userspace (i.e. you cannot remember the returned struct file * after
- *    returning to userspace).
- * 2) You must not call filp_close on the returned struct file * in between
- *    calls to fget_light and fput_light.
- * 3) You must not clone the current task in between the calls to fget_light
- *    and fput_light.
- *
- * The fput_needed flag returned by fget_light should be passed to the
- * corresponding fput_light.
- */
-struct file *fget_light(unsigned int fd, int *fput_needed)
+void fput(struct file *file)
 {
-	struct file *file;
-	struct files_struct *files = current->files;
-
-	*fput_needed = 0;
-	if (atomic_read(&files->count) == 1) {
-		file = fcheck_files(files, fd);
-		if (file && (file->f_mode & FMODE_PATH))
-			file = NULL;
-	} else {
-		rcu_read_lock();
-		file = fcheck_files(files, fd);
-		if (file) {
-			if (!(file->f_mode & FMODE_PATH) &&
-			    atomic_long_inc_not_zero(&file->f_count))
-				*fput_needed = 1;
-			else
-				/* Didn't get the reference, someone's freed */
-				file = NULL;
+	if (atomic_long_dec_and_test(&file->f_count)) {
+		struct task_struct *task = current;
+		file_sb_list_del(file);
+		if (unlikely(in_interrupt() || task->flags & PF_KTHREAD)) {
+			unsigned long flags;
+			spin_lock_irqsave(&delayed_fput_lock, flags);
+			list_add(&file->f_u.fu_list, &delayed_fput_list);
+			schedule_work(&delayed_fput_work);
+			spin_unlock_irqrestore(&delayed_fput_lock, flags);
+			return;
 		}
-		rcu_read_unlock();
+		init_task_work(&file->f_u.fu_rcuhead, ____fput);
+		task_work_add(task, &file->f_u.fu_rcuhead, true);
 	}
-
-	return file;
 }
 
-struct file *fget_raw_light(unsigned int fd, int *fput_needed)
+/*
+ * synchronous analog of fput(); for kernel threads that might be needed
+ * in some umount() (and thus can't use flush_delayed_fput() without
+ * risking deadlocks), need to wait for completion of __fput() and know
+ * for this specific struct file it won't involve anything that would
+ * need them.  Use only if you really need it - at the very least,
+ * don't blindly convert fput() by kernel thread to that.
+ */
+void __fput_sync(struct file *file)
 {
-	struct file *file;
-	struct files_struct *files = current->files;
-
-	*fput_needed = 0;
-	if (atomic_read(&files->count) == 1) {
-		file = fcheck_files(files, fd);
-	} else {
-		rcu_read_lock();
-		file = fcheck_files(files, fd);
-		if (file) {
-			if (atomic_long_inc_not_zero(&file->f_count))
-				*fput_needed = 1;
-			else
-				/* Didn't get the reference, someone's freed */
-				file = NULL;
-		}
-		rcu_read_unlock();
+	if (atomic_long_dec_and_test(&file->f_count)) {
+		struct task_struct *task = current;
+		file_sb_list_del(file);
+		BUG_ON(!(task->flags & PF_KTHREAD));
+		__fput(file);
 	}
-
-	return file;
 }
 
+EXPORT_SYMBOL(fput);
+
 void put_filp(struct file *file)
 {
 	if (atomic_long_dec_and_test(&file->f_count)) {
@@ -483,10 +445,8 @@ void mark_files_ro(struct super_block *sb)
 {
 	struct file *f;
 
-retry:
 	lg_global_lock(&files_lglock);
 	do_file_list_for_each_entry(sb, f) {
-		struct vfsmount *mnt;
 		if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
 		       continue;
 		if (!file_count(f))
@@ -498,13 +458,8 @@ retry:
 		spin_unlock(&f->f_lock);
 		if (file_check_writeable(f) != 0)
 			continue;
+		__mnt_drop_write(f->f_path.mnt);
 		file_release_write(f);
-		mnt = mntget(f->f_path.mnt);
-		/* This can sleep, so we can't hold the spinlock. */
-		lg_global_unlock(&files_lglock);
-		mnt_drop_write(mnt);
-		mntput(mnt);
-		goto retry;
 	} while_file_list_for_each_entry;
 	lg_global_unlock(&files_lglock);
 }