Re: [PATCH 1/3] readfile: implement readfile syscall
flat view
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2020-07-04 18:35:53
Also in:
linux-fsdevel, linux-kselftest, linux-man, lkml
Hi Greg, On Sat, Jul 4, 2020 at 4:05 PM Greg Kroah-Hartman [off-list ref] 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@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Thanks for your patch!
quoted hunk ↗ jump to hunk
--- a/fs/open.c +++ b/fs/open.c
quoted hunk ↗ jump to hunk
+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)?
quoted hunk ↗ jump to hunk
+ + filp_close(file, NULL); + + return retval; +}
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
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when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds