Re: [PATCH] Support systems without posix_memalign() and memalign()

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On 2012-05-02, at 12:30 PM, Theodore Ts'o wrote:
> MacOS 10.5 doesn't have posix_memalign() nor memalign(), but it does
> have valloc().  The Android SDK would like to be built on MacOS 10.5,
> so I've added support for a good-enough emulation of memalign()'s
> functionality using valloc(), with an explicit test to make sure
> valloc() is returning a pointer which is sufficiently aligned given
> the requested alignment.  This won't work if you try to operate on a
> file system with a 16k blocksize using an e2fsprogs built on MacOS
> 10.5 system, but it is good enough for the common case of 4k
> blocksize file systems, and we will let the memory allocation fail in
> the alignment is not good enough.

Won't this cause e.g. the 16kB/64kB blocksize regression tests to
fail on MacOS?  I've been assuming that the memalign functionality
is only necessary for O_DIRECT, which isn't even working on MacOS,
so it is enough to just return an unaligned memory chunk and it
will work for normal buffered IO on MacOS.

> I've also added a unit test for ext2fs_get_memalign() so we can be
> sure it's working as expected.  I've tested the code paths with
> HAVE_POSIX_MEMALIGN defined, HAVE_POSIX_MEMALIGN undefined, and
> HAVE_POSIX_MEMALIGN and HAVE_MEMALIGN undefined on an x86 Linux
> system, and so I know the valloc() code path works OK.  The simplistic
> (and less safe) patch at:
> 
> https://trac.macports.org/attachment/ticket/33692/patch-lib-ext2fs-inline.c.diff
> 
> Shows that using valloc() apparently works OK for MacOS 10.5 (but if
> it doesn't the unit test will catch a problem).
> 
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> lib/ext2fs/Makefile.in |    9 +++++++-
> lib/ext2fs/inline.c    |   56 ++++++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 62 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/ext2fs/Makefile.in b/lib/ext2fs/Makefile.in
> index 507a459..f9200fa 100644
> --- a/lib/ext2fs/Makefile.in
> +++ b/lib/ext2fs/Makefile.in
> @@ -369,6 +369,11 @@ tst_extents: $(srcdir)/extent.c extent_dbg.c $(DEBUG_OBJS) $(DEPLIBSS) \
> 		$(STATIC_LIBEXT2FS) $(LIBBLKID) $(LIBUUID) $(LIBCOM_ERR) \
> 		-I $(top_srcdir)/debugfs
> 
> +tst_inline: $(srcdir)/inline.c $(STATIC_LIBEXT2FS) $(DEPLIBCOM_ERR)
> +	$(E) "	LD $@"
> +	$(Q) $(CC) -o tst_inline $(srcdir)/inline.c $(ALL_CFLAGS) -DDEBUG \
> +		$(STATIC_LIBEXT2FS) $(LIBCOM_ERR)
> +
> tst_csum: csum.c $(STATIC_LIBEXT2FS) $(DEPLIBCOM_ERR) \
> 		$(top_srcdir)/lib/e2p/e2p.h
> 	$(E) "	LD $@"
> @@ -384,7 +389,8 @@ mkjournal: mkjournal.c $(STATIC_LIBEXT2FS) $(DEPLIBCOM_ERR)
> 	$(Q) $(CC) -o mkjournal $(srcdir)/mkjournal.c -DDEBUG $(STATIC_LIBEXT2FS) $(LIBCOM_ERR) $(ALL_CFLAGS)
> 
> check:: tst_bitops tst_badblocks tst_iscan tst_types tst_icount \
> -    tst_super_size tst_types tst_inode_size tst_csum tst_crc32c tst_bitmaps
> +    tst_super_size tst_types tst_inode_size tst_csum tst_crc32c tst_bitmaps \
> +    tst_inline
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_bitops
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_badblocks
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_iscan
> @@ -393,6 +399,7 @@ check:: tst_bitops tst_badblocks tst_iscan tst_types tst_icount \
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_super_size
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_inode_size
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_csum
> +	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_inline
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) ./tst_crc32c
> 	LD_LIBRARY_PATH=$(LIB) DYLD_LIBRARY_PATH=$(LIB) \
> 		./tst_bitmaps -f $(srcdir)/tst_bitmaps_cmds > tst_bitmaps_out
> diff --git a/lib/ext2fs/inline.c b/lib/ext2fs/inline.c
> index ad0c368..335db55 100644
> --- a/lib/ext2fs/inline.c
> +++ b/lib/ext2fs/inline.c
> @@ -45,7 +45,7 @@ errcode_t ext2fs_get_memalign(unsigned long size,
> 	errcode_t retval;
> 	void **p = ptr;
> 
> -	if (align == 0)
> +	if (align < 8)
> 		align = 8;
> #ifdef HAVE_POSIX_MEMALIGN
> 	retval = posix_memalign(p, align, size);
> @@ -64,9 +64,61 @@ errcode_t ext2fs_get_memalign(unsigned long size,
> 			return EXT2_ET_NO_MEMORY;
> 	}
> #else
> -#error memalign or posix_memalign must be defined!
> +#ifdef HAVE_VALLOC
> +	if (align > sizeof(long long))
> +		*p = valloc(size);
> +	else
> +#endif
> +		*p = malloc(size);
> +	if ((unsigned long) *p & (align - 1)) {
> +		free(*p);
> +		*p = 0;
> +	}
> +	if (*p == 0)
> +		return EXT2_ET_NO_MEMORY;
> #endif
> #endif
> 	return 0;
> }
> 
> +#ifdef DEBUG
> +static int isaligned(void *ptr, unsigned long align)
> +{
> +	return (((unsigned long) ptr & (align - 1)) == 0);
> +}
> +
> +static errcode_t test_memalign(unsigned long align)
> +{
> +	void *ptr = 0;
> +	errcode_t retval;
> +
> +	retval = ext2fs_get_memalign(32, align, &ptr);
> +	if (!retval && !isaligned(ptr, align))
> +		retval = EINVAL;
> +	free(ptr);
> +	printf("tst_memliagn(%lu): %s\n", align, 
> +	       retval ? error_message(retval) : "OK");
> +	return retval;
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	int err = 0;
> +
> +	if (test_memalign(4))
> +		err++;
> +	if (test_memalign(32))
> +		err++;
> +	if (test_memalign(1024))
> +		err++;
> +	if (test_memalign(4096))
> +		err++;
> +#if defined(HAVE_POSIX_MEMALIGN) || defined(HAVE_MEMALIGN)
> +	if (test_memalign(16384))
> +		err++;
> +	if (test_memalign(32768))
> +		err++;
> +#endif
> +	return err;
> +}
> +#endif
> -- 
> 1.7.10.rc3
> 
> --
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Cheers, Andreas





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