From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Brauner Subject: Re: [PATCH v1 1/2] open: add close_range() Date: Thu, 23 May 2019 13:51:20 +0200 Message-ID: <20190523115118.pmscbd6kaqy37dym@brauner.io> References: <20190522155259.11174-1-christian@brauner.io> <20190522165737.GC4915@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <20190522165737.GC4915@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Oleg Nesterov Cc: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, torvalds@linux-foundation.org, fweimer@redhat.com, jannh@google.com, tglx@linutronix.de, arnd@arndb.de, shuah@kernel.org, dhowells@redhat.com, tkjos@android.com, ldv@altlinux.org, miklos@szeredi.hu, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, x86@kernel.org List-ID: On Wed, May 22, 2019 at 06:57:37PM +0200, Oleg Nesterov wrote: > On 05/22, Christian Brauner wrote: > > > > +static struct file *pick_file(struct files_struct *files, unsigned fd) > > { > > - struct file *file; > > + struct file *file = NULL; > > struct fdtable *fdt; > > > > spin_lock(&files->file_lock); > > @@ -632,15 +629,65 @@ int __close_fd(struct files_struct *files, unsigned fd) > > goto out_unlock; > > rcu_assign_pointer(fdt->fd[fd], NULL); > > __put_unused_fd(files, fd); > > - spin_unlock(&files->file_lock); > > - return filp_close(file, files); > > > > out_unlock: > > spin_unlock(&files->file_lock); > > - return -EBADF; > > + return file; > > ... > > > +int __close_range(struct files_struct *files, unsigned fd, unsigned max_fd) > > +{ > > + unsigned int cur_max; > > + > > + if (fd > max_fd) > > + return -EINVAL; > > + > > + rcu_read_lock(); > > + cur_max = files_fdtable(files)->max_fds; > > + rcu_read_unlock(); > > + > > + /* cap to last valid index into fdtable */ > > + if (max_fd >= cur_max) > > + max_fd = cur_max - 1; > > + > > + while (fd <= max_fd) { > > + struct file *file; > > + > > + file = pick_file(files, fd++); > > Well, how about something like > > static unsigned int find_next_opened_fd(struct fdtable *fdt, unsigned start) > { > unsigned int maxfd = fdt->max_fds; > unsigned int maxbit = maxfd / BITS_PER_LONG; > unsigned int bitbit = start / BITS_PER_LONG; > > bitbit = find_next_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG; > if (bitbit > maxfd) > return maxfd; > if (bitbit > start) > start = bitbit; > return find_next_bit(fdt->open_fds, maxfd, start); > } > > unsigned close_next_fd(struct files_struct *files, unsigned start, unsigned maxfd) > { > unsigned fd; > struct file *file; > struct fdtable *fdt; > > spin_lock(&files->file_lock); > fdt = files_fdtable(files); > fd = find_next_opened_fd(fdt, start); > if (fd >= fdt->max_fds || fd > maxfd) { > fd = -1; > goto out; > } > > file = fdt->fd[fd]; > rcu_assign_pointer(fdt->fd[fd], NULL); > __put_unused_fd(files, fd); > out: > spin_unlock(&files->file_lock); > > if (fd == -1u) > return fd; > > filp_close(file, files); > return fd + 1; > } Thanks, Oleg! I kept it dumb and was about to reply that your solution introduces more code when it seemed we wanted to keep this very simple for now. But then I saw that find_next_opened_fd() already exists as find_next_fd(). So it's actually not bad compared to what I sent in v1. So - with some small tweaks (need to test it and all now) - how do we feel about?: /** * __close_next_open_fd() - Close the nearest open fd. * * @curfd: lowest file descriptor to consider * @maxfd: highest file descriptor to consider * * This function will close the nearest open fd, i.e. it will either * close @curfd if it is open or the closest open file descriptor * c greater than @curfd that * is smaller or equal to maxfd. * If the function found a file descriptor to close it will return 0 and * place the file descriptor it closed in @curfd. If it did not find a * file descriptor to close it will return -EBADF. */ static int __close_next_open_fd(struct files_struct *files, unsigned *curfd, unsigned maxfd) { struct file *file = NULL; unsigned fd; struct fdtable *fdt; spin_lock(&files->file_lock); fdt = files_fdtable(files); fd = find_next_fd(fdt, *curfd); if (fd >= fdt->max_fds || fd > maxfd) goto out_unlock; file = fdt->fd[fd]; rcu_assign_pointer(fdt->fd[fd], NULL); __put_unused_fd(files, fd); out_unlock: spin_unlock(&files->file_lock); if (!file) return -EBADF; *curfd = fd; filp_close(file, files); return 0; } int __close_range(struct files_struct *files, unsigned fd, unsigned max_fd) { if (fd > max_fd) return -EINVAL; while (fd <= max_fd) { if (__close_next_fd(files, &fd, maxfd)) break; cond_resched(); fd++; } return 0; } SYSCALL_DEFINE3(close_range, unsigned int, fd, unsigned int, max_fd, unsigned int, flags) { if (flags) return -EINVAL; return __close_range(current->files, fd, max_fd); }