diff options
Diffstat (limited to 'fs/file_table.c')
| -rw-r--r-- | fs/file_table.c | 81 |
1 files changed, 71 insertions, 10 deletions
diff --git a/fs/file_table.c b/fs/file_table.c index a305d9e2d1b2..b3fc4d67a26b 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> @@ -251,7 +253,6 @@ static void __fput(struct file *file) } 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) @@ -263,10 +264,77 @@ static void __fput(struct file *file) mntput(mnt); } +static DEFINE_SPINLOCK(delayed_fput_lock); +static LIST_HEAD(delayed_fput_list); +static void delayed_fput(struct work_struct *unused) +{ + 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); + } +} + +static void ____fput(struct callback_head *work) +{ + __fput(container_of(work, struct file, f_u.fu_rcuhead)); +} + +/* + * 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) +{ + delayed_fput(NULL); +} + +static DECLARE_WORK(delayed_fput_work, delayed_fput); + void fput(struct file *file) { - if (atomic_long_dec_and_test(&file->f_count)) + 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; + } + init_task_work(&file->f_u.fu_rcuhead, ____fput); + task_work_add(task, &file->f_u.fu_rcuhead, true); + } +} + +/* + * 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) +{ + 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); + } } EXPORT_SYMBOL(fput); @@ -483,10 +551,8 @@ 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)) @@ -499,12 +565,7 @@ retry: if (file_check_writeable(f) != 0) continue; 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; + mnt_drop_write_file(f); } while_file_list_for_each_entry; lg_global_unlock(&files_lglock); } |