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Date: Sat, 4 Jul 2020 20:35:36 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: Al Viro <viro@...iv.linux.org.uk>, "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>, Shuah Khan <shuah@...nel.org>, Linux API <linux-api@...r.kernel.org>, Linux FS Devel <linux-fsdevel@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-man@...r.kernel.org, "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org> Subject: Re: [PATCH 1/3] readfile: implement readfile syscall Hi Greg, On Sat, Jul 4, 2020 at 4:05 PM Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote: > It's a tiny syscall, meant to allow a user to do a single "open this > file, read into this buffer, and close the file" all in a single shot. > > Should be good for reading "tiny" files like sysfs, procfs, and other > "small" files. > > There is no restarting the syscall, this is a "simple" syscall, with the > attempt to make reading "simple" files easier with less syscall > overhead. > > Cc: Alexander Viro <viro@...iv.linux.org.uk> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Thanks for your patch! > --- a/fs/open.c > +++ b/fs/open.c > +SYSCALL_DEFINE5(readfile, int, dfd, const char __user *, filename, > + char __user *, buffer, size_t, bufsize, int, flags) > +{ > + struct open_flags op; > + struct open_how how; > + struct file *file; > + loff_t pos = 0; > + int retval; > + > + /* only accept a small subset of O_ flags that make sense */ > + if ((flags & (O_NOFOLLOW | O_NOATIME)) != flags) > + return -EINVAL; > + > + /* add some needed flags to be able to open the file properly */ > + flags |= O_RDONLY | O_LARGEFILE; > + > + how = build_open_how(flags, 0000); > + retval = build_open_flags(&how, &op); > + if (retval) > + return retval; > + > + file = readfile_open(dfd, filename, &op); > + if (IS_ERR(file)) > + return PTR_ERR(file); > + > + retval = vfs_read(file, buffer, bufsize, &pos); Should there be a way for the user to be informed that the file doesn't fit in the provided buffer (.e.g. -EFBIG)? > + > + filp_close(file, NULL); > + > + return retval; > +} Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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