This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] test-container: Use xcopy_file_range for cross-device copy [BZ #23597]
- From: Carlos O'Donell <carlos at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Fri, 31 Aug 2018 14:47:40 -0400
- Subject: Re: [PATCH] test-container: Use xcopy_file_range for cross-device copy [BZ #23597]
- References: <CAMe9rOodYBvH6j-J8MKGq06t0KDg+gMpVyXWsR_bqK9OMO0+Ow@mail.gmail.com>
On 08/31/2018 02:33 PM, H.J. Lu wrote:
> On Fri, Aug 31, 2018 at 9:23 AM, Carlos O'Donell <carlos@redhat.com> wrote:
>>> That is what io/copy_file_range-compat.c does. Are you suggesting
>>> cut and paste, instead of #include?
>> Not quite.
>>
>> We are suggesting a unique and simplified copy of those sources to
>> be placed into the support/ directory as a *.c file that can be
>> used for support purposes.
>>
>> Coupling support behaviour and runtime behaviour is a bad choice,
>> so we should not do it. Even if it means some code duplication.
>>
> Like this?
Almost. Look at the notes below and I'll review a v3.
> -- H.J.
>
>
> 0001-test-container-Use-xcopy_file_range-for-cross-device.patch
>
>
> From f08d598bcc973c4747d6baa1a832d683f2c917a8 Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Fri, 31 Aug 2018 11:26:16 -0700
> Subject: [PATCH] test-container: Use xcopy_file_range for cross-device copy
> [BZ #23597]
>
> copy_file_range can't be used to copy a file from glibc source directory
> to glibc build directory since they may be on different filesystems.
> This patch adds xcopy_file_range to use it for cross-device copy.
>
> [BZ #23597]
> * support/Makefile (libsupport-routines): Add xcopy_file_range.
> * support/test-container.c (copy_one_file): Call xcopy_file_rang
> instead of copy_file_range.
> * support/xcopy_file_range.c: New file. Copied and modified
> from io/copy_file_range-compat.c.
> * support/xunistd.h (xcopy_file_range): New prototype.
> ---
> support/Makefile | 1 +
> support/test-container.c | 2 +-
> support/xcopy_file_range.c | 142 +++++++++++++++++++++++++++++++++++++
> support/xunistd.h | 3 +
> 4 files changed, 147 insertions(+), 1 deletion(-)
> create mode 100644 support/xcopy_file_range.c
>
> diff --git a/support/Makefile b/support/Makefile
> index b528f538a6..7758465bb7 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -74,6 +74,7 @@ libsupport-routines = \
> xchroot \
> xclose \
> xconnect \
> + xcopy_file_range \
OK.
> xdlfcn \
> xdup2 \
> xfclose \
> diff --git a/support/test-container.c b/support/test-container.c
> index 2e91bdf9ec..476a5574e6 100644
> --- a/support/test-container.c
> +++ b/support/test-container.c
> @@ -383,7 +383,7 @@ copy_one_file (const char *sname, const char *dname)
> if (dfd < 0)
> FAIL_EXIT1 ("unable to open %s for writing\n", dname);
>
> - if (copy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
> + if (xcopy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
No. This should just be:
xcopy_file_range( ... );
You expect xcopy_file_range to handle all the errors.
Rather than hack up the function itself though you might want to:
- Create support_copy_file_range which is the real function and
returns errors, and is documented as doing that.
- Create a xcopy_file_range which is a wrapper that detects errors
and calls support_copy_file_range, and for each error it calls
FAIL_EXIT with an appropriate error message. So a caller knows it
always succeeds (simplifies tests).
> FAIL_EXIT1 ("cannot copy file %s to %s\n", sname, dname);
>
> xclose (sfd);
> diff --git a/support/xcopy_file_range.c b/support/xcopy_file_range.c
> new file mode 100644
> index 0000000000..e6ba141eee
> --- /dev/null
> +++ b/support/xcopy_file_range.c
> @@ -0,0 +1,142 @@
> +/* Simplified copy_file_range with cross-device copy
> + Copyright (C) 2018 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <inttypes.h>
> +#include <limits.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +
> +ssize_t
> +xcopy_file_range (int infd, __off64_t *pinoff,
> + int outfd, __off64_t *poutoff,
> + size_t length, unsigned int flags)
> +{
> + if (flags != 0)
> + {
> + errno = EINVAL;
> + return -1;
> + }
> +
> + struct stat64 instat;
> + struct stat64 outstat;
> + if (fstat64 (infd, &instat) != 0 || fstat64 (outfd, &outstat) != 0)
> + return -1;
> + if (S_ISDIR (instat.st_mode) || S_ISDIR (outstat.st_mode))
> + {
> + errno = EISDIR;
> + return -1;
> + }
> + if (!S_ISREG (instat.st_mode) || !S_ISREG (outstat.st_mode))
> + {
> + /* We need a regular input file so that the we can seek
> + backwards in case of a write failure. */
> + errno = EINVAL;
> + return -1;
> + }
> +
> + /* The output descriptor must not have O_APPEND set. */
> + if (fcntl (outfd, F_GETFL) & O_APPEND)
> + {
> + errno = EBADF;
> + return -1;
> + }
> +
> + /* Avoid an overflow in the result. */
> + if (length > SSIZE_MAX)
> + length = SSIZE_MAX;
> +
> + /* Main copying loop. The buffer size is arbitrary and is a
> + trade-off between stack size consumption, cache usage, and
> + amortization of system call overhead. */
> + size_t copied = 0;
> + char buf[8192];
> + while (length > 0)
> + {
> + size_t to_read = length;
> + if (to_read > sizeof (buf))
> + to_read = sizeof (buf);
> +
> + /* Fill the buffer. */
> + ssize_t read_count;
> + if (pinoff == NULL)
> + read_count = read (infd, buf, to_read);
> + else
> + read_count = pread64 (infd, buf, to_read, *pinoff);
> + if (read_count == 0)
> + /* End of file reached prematurely. */
> + return copied;
> + if (read_count < 0)
> + {
> + if (copied > 0)
> + /* Report the number of bytes copied so far. */
> + return copied;
> + return -1;
> + }
> + if (pinoff != NULL)
> + *pinoff += read_count;
> +
> + /* Write the buffer part which was read to the destination. */
> + char *end = buf + read_count;
> + for (char *p = buf; p < end; )
> + {
> + ssize_t write_count;
> + if (poutoff == NULL)
> + write_count = write (outfd, p, end - p);
> + else
> + write_count = pwrite64 (outfd, p, end - p, *poutoff);
> + if (write_count < 0)
> + {
> + /* Adjust the input read position to match what we have
> + written, so that the caller can pick up after the
> + error. */
> + size_t written = p - buf;
> + /* NB: This needs to be signed so that we can form the
> + negative value below. */
> + ssize_t overread = read_count - written;
> + if (pinoff == NULL)
> + {
> + if (overread > 0)
> + {
> + /* We are on an error recovery path, so we
> + cannot deal with failure here. */
> + int save_errno = errno;
> + (void) lseek64 (infd, -overread, SEEK_CUR);
> + errno = save_errno;
> + }
> + }
> + else /* pinoff != NULL */
> + *pinoff -= overread;
> +
> + if (copied + written > 0)
> + /* Report the number of bytes copied so far. */
> + return copied + written;
> + return -1;
> + }
> + p += write_count;
> + if (poutoff != NULL)
> + *poutoff += write_count;
> + } /* Write loop. */
> +
> + copied += read_count;
> + length -= read_count;
> + }
> + return copied;
> +}
There are 6 error return paths here that should be handled by the
xcopy_file_range wrapper.
> diff --git a/support/xunistd.h b/support/xunistd.h
> index cdd4e8d92d..f99f362cb4 100644
> --- a/support/xunistd.h
> +++ b/support/xunistd.h
> @@ -64,6 +64,9 @@ void *xmmap (void *addr, size_t length, int prot, int flags, int fd);
> void xmprotect (void *addr, size_t length, int prot);
> void xmunmap (void *addr, size_t length);
>
> +ssize_t xcopy_file_range(int fd_in, loff_t *off_in, int fd_out,
> + loff_t *off_out, size_t len, unsigned int flags);
OK.
> +
> __END_DECLS
>
> #endif /* SUPPORT_XUNISTD_H */
> -- 2.17.1
--
Cheers,
Carlos.