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Re: [PATCH] io: Avoid running some tests if the file system does not support holes
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Fri, 13 Jul 2018 15:43:51 -0300
- Subject: Re: [PATCH] io: Avoid running some tests if the file system does not support holes
- References: <20180713121033.7626643994575@oldenburg.str.redhat.com>
On 13/07/2018 09:10, Florian Weimer wrote:
> Otherwise, these tests fills up the entire disk (or just run very slowly
> and eventually time out).
>
> 2018-07-13 Florian Weimer <fweimer@redhat.com>
>
> * support/support_descriptor_supports_holes.c: New file.
> * support/Makefile (libsupport-routines): Add
> support_descriptor_supports_holes.
> * support/support.h (support_descriptor_supports_holes): Declare.
> * io/tst-copy_file_range.c: Call support_descriptor_supports_holes
> and stop testing if holes are not supported.
> * io/test-lfs.c (do_prepare): Likewise.
> * sysdeps/unix/sysv/linux/tst-fallocate-common.c (do_prepare):
> Likewise.
LGTM with just a clarification below.
>
> diff --git a/io/test-lfs.c b/io/test-lfs.c
> index f7721a5995..52120e9bca 100644
> --- a/io/test-lfs.c
> +++ b/io/test-lfs.c
> @@ -25,6 +25,7 @@
> #include <error.h>
> #include <errno.h>
> #include <sys/resource.h>
> +#include <support/check.h>
>
> /* Prototype for our test function. */
> extern void do_prepare (int argc, char *argv[]);
> @@ -70,6 +71,8 @@ do_prepare (int argc, char *argv[])
> else
> error (EXIT_FAILURE, errno, "cannot create temporary file");
> }
> + if (!support_descriptor_supports_holes (fd))
> + FAIL_UNSUPPORTED ("File %s does not support holes", name);
> add_temp_file (name);
>
> if (getrlimit64 (RLIMIT_FSIZE, &rlim) != 0)
> diff --git a/io/tst-copy_file_range.c b/io/tst-copy_file_range.c
> index 3d531a1937..e5b46f91db 100644
> --- a/io/tst-copy_file_range.c
> +++ b/io/tst-copy_file_range.c
> @@ -739,7 +739,12 @@ do_test (void)
> *p = rand () >> 24;
>
> infd = create_temp_file ("tst-copy_file_range-in-", &infile);
> - xclose (create_temp_file ("tst-copy_file_range-out-", &outfile));
> + {
> + int outfd = create_temp_file ("tst-copy_file_range-out-", &outfile);
> + if (!support_descriptor_supports_holes (outfd))
> + FAIL_UNSUPPORTED ("File %s does not support holes", outfile);
> + xclose (outfd);
> + }
>
> /* Try to find a different directory from the default input/output
> file. */
> diff --git a/support/Makefile b/support/Makefile
> index 652d2cdf69..9063046c23 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -43,6 +43,7 @@ libsupport-routines = \
> support_capture_subprocess \
> support_capture_subprocess_check \
> support_chroot \
> + support_descriptor_supports_holes \
> support_enter_mount_namespace \
> support_enter_network_namespace \
> support_format_address_family \
> diff --git a/support/support.h b/support/support.h
> index b61fe0735c..34ae6e10cd 100644
> --- a/support/support.h
> +++ b/support/support.h
> @@ -65,6 +65,12 @@ void support_write_file_string (const char *path, const char *contents);
> the result). */
> char *support_quote_blob (const void *blob, size_t length);
>
> +/* Returns non-zero if the file descriptor is a regular file on a file
> + system which supports holes (that is, seeking and writing does not
> + allocate storage for the range of zeros). FD must refer to a
> + regular file open for writing, and initially empty. */
> +int support_descriptor_supports_holes (int fd);
> +
> /* Error-checking wrapper functions which terminate the process on
> error. */
>
> diff --git a/support/support_descriptor_supports_holes.c b/support/support_descriptor_supports_holes.c
> new file mode 100644
> index 0000000000..b04498664e
> --- /dev/null
> +++ b/support/support_descriptor_supports_holes.c
> @@ -0,0 +1,80 @@
> +/* Test for file system hole support.
> + 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 <stdbool.h>
> +#include <support.h>
> +#include <support/check.h>
> +#include <sys/stat.h>
> +#include <xunistd.h>
> +
> +int
> +support_descriptor_supports_holes (int fd)
> +{
> + enum
> + {
> + /* Write offset for the enlarged file. This value is arbitrary
> + and hopefully large enough to trigger the creation of holes.
> + We cannot use the file system block size as a reference here
> + because it is incorrect for network file systems. */
> + write_offset = 16 * 1024 * 1024,
> +
> + /* Our write may add this number of additional blocks. */
> + block_headroom = 8,
Is this number based on 512 physical block size with a 4kb page size?
If so, shouldn't we try to determine this at runtime?
> + };
> +
> + struct stat64 st;
> + xfstat (fd, &st);
> + if (!S_ISREG (st.st_mode))
> + FAIL_EXIT1 ("descriptor %d does not refer to a regular file", fd);
> + if (st.st_size != 0)
> + FAIL_EXIT1 ("descriptor %d does not refer to an empty file", fd);
> + if (st.st_blocks > block_headroom)
> + FAIL_EXIT1 ("descriptor %d refers to a pre-allocated file (%lld blocks)",
> + fd, (long long int) st.st_blocks);
> +
> + /* Write a single byte at the start of the file to compute the block
> + usage for a single byte. */
> + xlseek (fd, 0, SEEK_SET);
> + char b = '@';
> + xwrite (fd, &b, 1);
> + /* Attempt to bypass delayed allocation. */
> + TEST_COMPARE (fsync (fd), 0);
> + xfstat (fd, &st);
> + unsigned long long int block_limit = 2 * st.st_blocks + block_headroom;
> +
> + /* Write a single byte at 16 megabytes. */
> + xlseek (fd, write_offset, SEEK_SET);
> + xwrite (fd, &b, 1);
> + /* Attempt to bypass delayed allocation. */
> + TEST_COMPARE (fsync (fd), 0);
> + xfstat (fd, &st);
> + bool supports_holes = st.st_blocks <= block_limit;
> +
> + /* Also check that extending the file does not fill up holes. */
> + xftruncate (fd, 2 * write_offset);
> + /* Attempt to bypass delayed allocation. */
> + TEST_COMPARE (fsync (fd), 0);
> + xfstat (fd, &st);
> + supports_holes = supports_holes && st.st_blocks <= block_limit;
> +
> + /* Return to a zero-length file. */
> + xftruncate (fd, 0);
> + xlseek (fd, 0, SEEK_SET);
> +
> + return supports_holes;
> +}
> diff --git a/sysdeps/unix/sysv/linux/tst-fallocate-common.c b/sysdeps/unix/sysv/linux/tst-fallocate-common.c
> index a6ba403c62..bc54cf5134 100644
> --- a/sysdeps/unix/sysv/linux/tst-fallocate-common.c
> +++ b/sysdeps/unix/sysv/linux/tst-fallocate-common.c
> @@ -41,6 +41,8 @@ do_prepare (int argc, char **argv)
> temp_fd = create_temp_file ("tst-fallocate.", &temp_filename);
> if (temp_fd == -1)
> FAIL_EXIT1 ("cannot create temporary file: %m");
> + if (!support_descriptor_supports_holes (temp_fd))
> + FAIL_UNSUPPORTED ("File %s does not support holes", temp_filename);
> }
> #define PREPARE do_prepare
>
>