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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: containers-bounces@lists.linux-foundation.org Sender: "Containers" Christian Brauner writes: > On Tue, Oct 13, 2020 at 04:06:08PM +0200, Giuseppe Scrivano wrote: > > Hey Guiseppe, > > Thanks for the patch! > >> When the flag CLOSE_RANGE_CLOEXEC is set, close_range doesn't >> immediately close the files but it sets the close-on-exec bit. > > Hm, please expand on the use-cases a little here so people know where > and how this is useful. Keeping the rationale for a change in the commit > log is really important. > >> >> Signed-off-by: Giuseppe Scrivano >> --- > >> fs/file.c | 56 ++++++++++++++++++++++---------- >> include/uapi/linux/close_range.h | 3 ++ >> 2 files changed, 42 insertions(+), 17 deletions(-) >> >> diff --git a/fs/file.c b/fs/file.c >> index 21c0893f2f1d..ad4ebee41e09 100644 >> --- a/fs/file.c >> +++ b/fs/file.c >> @@ -672,6 +672,17 @@ int __close_fd(struct files_struct *files, unsigned fd) >> } >> EXPORT_SYMBOL(__close_fd); /* for ksys_close() */ >> >> +static unsigned int __get_max_fds(struct files_struct *cur_fds) >> +{ >> + unsigned int max_fds; >> + >> + rcu_read_lock(); >> + /* cap to last valid index into fdtable */ >> + max_fds = files_fdtable(cur_fds)->max_fds; >> + rcu_read_unlock(); >> + return max_fds; >> +} >> + >> /** >> * __close_range() - Close all file descriptors in a given range. >> * >> @@ -683,27 +694,23 @@ EXPORT_SYMBOL(__close_fd); /* for ksys_close() */ >> */ >> int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) >> { >> - unsigned int cur_max; >> + unsigned int cur_max = UINT_MAX; >> struct task_struct *me = current; >> struct files_struct *cur_fds = me->files, *fds = NULL; >> >> - if (flags & ~CLOSE_RANGE_UNSHARE) >> + if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC)) >> return -EINVAL; >> >> if (fd > max_fd) >> return -EINVAL; >> >> - rcu_read_lock(); >> - cur_max = files_fdtable(cur_fds)->max_fds; >> - rcu_read_unlock(); >> - >> - /* cap to last valid index into fdtable */ >> - cur_max--; >> - >> if (flags & CLOSE_RANGE_UNSHARE) { >> int ret; >> unsigned int max_unshare_fds = NR_OPEN_MAX; >> >> + /* cap to last valid index into fdtable */ >> + cur_max = __get_max_fds(cur_fds) - 1; >> + >> /* >> * If the requested range is greater than the current maximum, >> * we're closing everything so only copy all file descriptors >> @@ -724,16 +731,31 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) >> swap(cur_fds, fds); >> } >> >> - max_fd = min(max_fd, cur_max); >> - while (fd <= max_fd) { >> - struct file *file; >> + if (flags & CLOSE_RANGE_CLOEXEC) { >> + struct fdtable *fdt; >> >> - file = pick_file(cur_fds, fd++); >> - if (!file) >> - continue; >> + spin_lock(&cur_fds->file_lock); >> + fdt = files_fdtable(cur_fds); >> + cur_max = fdt->max_fds - 1; >> + max_fd = min(max_fd, cur_max); >> + while (fd <= max_fd) >> + __set_close_on_exec(fd++, fdt); >> + spin_unlock(&cur_fds->file_lock); >> + } else { >> + /* Initialize cur_max if needed. */ >> + if (cur_max == UINT_MAX) >> + cur_max = __get_max_fds(cur_fds) - 1; > > The separation between how cur_fd is retrieved in the two branches makes > the code more difficult to follow imho. Unless there's a clear reason > why you've done it that way I would think that something like the patch > I appended below might be a little clearer and easier to maintain(?). Thanks for the review! I've opted for this version as in the flags=CLOSE_RANGE_CLOEXEC case we can read max_fds directly from the fds table and avoid doing it from the RCU critical section as well. I'll change it in favor of more readable code. Giuseppe _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/containers