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linux: statvfs: allocate spare for f_type

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This is the only missing part in struct statvfs.
The LSB calls [f]statfs() deprecated, and its weird types are definitely
off-putting. However, its use is required to get f_type.

Instead, allocate one of the six spares to f_type,
copied directly from struct statfs.
This then becomes a small glibc extension to the standard interface
on Linux and the Hurd, instead of two different interfaces, one of which
is quite odd due to being an ABI type, and there no longer is any reason
to use statfs().

The underlying kernel type is a mess, but all architectures agree on u32
(or more) for the ABI, and all filesystem magicks are 32-bit integers.
We don't lose any generality by using u32, and by doing so we both make
the API consistent with the Hurd, and allow C++
  switch(f_type) { case RAMFS_MAGIC: ...; }

Also fix tst-statvfs so that it actually fails;
as it stood, all it did was return 0 always.
Test statfs()' and statvfs()' f_types are the same.

Link: https://lore.kernel.org/linux-man/f54kudgblgk643u32tb6at4cd3kkzha6hslahv24szs4raroaz@ogivjbfdaqtb/t/#u
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
наб 2023-08-06 22:23:36 +02:00 committed by Adhemerval Zanella
parent a9847e2c66
commit 92861d93cd
4 changed files with 21 additions and 11 deletions
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5
NEWS
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@ -9,7 +9,10 @@ Version 2.39
Major new features:
[Add new features here]
* struct statvfs now has an f_type member, equal to the f_type statfs member;
on the Hurd this was always available under a reserved name,
and under Linux a spare has been allocated: it was always zero
in previous versions of glibc, and zero is not a valid result.
Deprecated and removed features, and other changes affecting compatibility:

19
io/tst-statvfs.c
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@ -1,5 +1,7 @@
#include <stdio.h>
#include <sys/statfs.h>
#include <sys/statvfs.h>
#include <support/check.h>
/* This test cannot detect many errors. But it will fail if the
@ -11,17 +13,18 @@ do_test (int argc, char *argv[])
for (int i = 1; i < argc; ++i)
{
struct statvfs st;
if (statvfs (argv[i], &st) != 0)
printf ("%s: failed (%m)\n", argv[i]);
else
printf ("%s: free: %llu, mandatory: %s\n", argv[i],
(unsigned long long int) st.f_bfree,
struct statfs stf;
TEST_COMPARE (statvfs (argv[i], &st), 0);
TEST_COMPARE (statfs (argv[i], &stf), 0);
TEST_COMPARE (st.f_type, stf.f_type);
printf ("%s: free: %llu, mandatory: %s, tp=%x\n", argv[i],
(unsigned long long int) st.f_bfree,
#ifdef ST_MANDLOCK
(st.f_flag & ST_MANDLOCK) ? "yes" : "no"
(st.f_flag & ST_MANDLOCK) ? "yes" : "no",
#else
"no"
"no",
#endif
);
st.f_type);
}
return 0;
}

6
sysdeps/unix/sysv/linux/bits/statvfs.h
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@ -51,7 +51,8 @@ struct statvfs
#endif
unsigned long int f_flag;
unsigned long int f_namemax;
int __f_spare[6];
unsigned int f_type;
int __f_spare[5];
};
#ifdef __USE_LARGEFILE64
@ -71,7 +72,8 @@ struct statvfs64
#endif
unsigned long int f_flag;
unsigned long int f_namemax;
int __f_spare[6];
unsigned int f_type;
int __f_spare[5];
};
#endif

2
sysdeps/unix/sysv/linux/internal_statvfs.c
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@ -57,6 +57,7 @@ __internal_statvfs (struct statvfs *buf, const struct statfs *fsbuf)
buf->__f_unused = 0;
#endif
buf->f_namemax = fsbuf->f_namelen;
buf->f_type = fsbuf->f_type;
memset (buf->__f_spare, '\0', sizeof (buf->__f_spare));
/* What remains to do is to fill the fields f_favail and f_flag. */
@ -99,6 +100,7 @@ __internal_statvfs64 (struct statvfs64 *buf, const struct statfs64 *fsbuf)
buf->__f_unused = 0;
#endif
buf->f_namemax = fsbuf->f_namelen;
buf->f_type = fsbuf->f_type;
memset (buf->__f_spare, '\0', sizeof (buf->__f_spare));
/* What remains to do is to fill the fields f_favail and f_flag. */