So far statx_mount_same() assumed STATX_MNT_ID_UNIQUE didn't exist.
However it does exist, hence do something useful if we see it set. Note
that this creates a certain ambiguity: if we compare one statx struct
with STATX_MNT_ID_UNIQUE and one without it (but with the regular mnt
id), then we cnanot really come to a clear conclusion, hence need to
introduce a third, unknown state.
Note that we don't request STATX_MNT_ID_UNIQUE yet wherever we call
statx_mount_same(). THis will be added in a later commit.
name_to_handle_at_try_unique_mntid_fid() in its current form is
ill-designed for various reasons:
* AT_HANDLE_FID requires file system support, while unique mount id
is a VFS concept hence is always available if supported. Hence
the fallback for AT_HANDLE_MNT_ID_UNIQUE should be independent
of fid.
* The request for AT_HANDLE_MNT_ID_UNIQUE can be identified via
specifying ret_unique_mnt_id, no need for opening up the control
to caller (and currently the function simply doesn't handle
mismatch between ret params and flags).
* The caller cannot realistically differentiate whether the returned
mount id is actually unique.
* The path_get_unique_mnt_id() fallback did not handle AT_SYMLINK_FOLLOW.
Let's instead move the statx() fallback into name_to_handle_at_loop()
directly, and revamp interaction of ret_mnt_id/ret_unique_mnt_id:
if both are set, it indicates that the caller can handle both, hence
set what we have and return 0/1 for whether we managed to acquire
the unique one.
The !ret_handle && ret_mnt_id logic is removed. Let's not rely on
undocumented bizaare behavior and it's unused anyways.
path_get_mnt_id_at() exists for a reason...
Typically, proc_mounted() is used in error handling. Hence, it is better
to make it not update the original errno.
Currently, there are two places that returns wrong error code:
- pidref_get_capability() in src/basic/capability-util.c
```c
_cleanup_fclose_ FILE *f = fopen(path, "re");
if (!f) {
if (errno == ENOENT && proc_mounted() == 0)
return -ENOSYS;
return -errno;
}
```
- fdset_new_fill() in src/shared/fdset.c
```c
d = opendir("/proc/self/fd");
if (!d) {
if (errno == ENOENT && proc_mounted() == 0)
return -ENOSYS;
return -errno;
}
```
Rather than fixing them, let's make proc_mounted() not update errno,
otherwise we may make a similar failure in a future.
I was looking at strace for systemd-getty-generator and noticed the call to
faccessat2(3</sys>, "", W_OK, AT_EMPTY_PATH), even though we already did
fstatfs(3</sys>), which should give us all the necessary information. Let's
only do this additional check when it's likely to yield something useful, i.e.
for network fses and otherwise skip the syscall.
The call to statvfs is replaced by statfs because that gives us the .f_type
field and allows is_network_fs() to be called.
I'm a bit worried that the is_network_fs() is somewhat costly. This will be
improved in later commits.
This partially reverts e86a492ff0.
The function getdents64() was introduced in glibc-2.30, and our baseline
on glibc is 2.31. Hence, we can assume the function always exists.
The posix_getdents() wrapper was introduced for compatibility with musl.
However, even the latest release of musl does not provide posix_getdents()
yet. Also, even with musl, by defining _LARGEFILE64_SOURCE, we can get
getdents64() and struct dirent64. Hence, the wrapper is anyway not
necessary.
Now that the necessary functions from log.h have been moved to macro.h,
we can stop including log.h in macro.h. This requires modifying source
files all over the tree to include log.h instead.
glibc exports getdents64 syscall as is, but musl exports it as
posix_getdents(). Let's introduce a simple wrapper of posix_getdents().
Note, our baseline for glibc is 2.31. Hence, we can assume getdents64()
always defined when building with glibc.
struct statx in glibc header was introduced in glibc-2.28
(fd70af45528d59a00eb3190ef6706cb299488fcd), but at that time,
sys/stat.h conflicts with linux/stat.h. Since glibc-2.30
(5dad6ffbb2b76215cfcd38c3001778536ada8e8a), sys/stat.h includes
linux/stat.h if exists.
Since now our baseline of glibc is 2.31. Hence, we can drop workarounds
for struct statx by importing linux/stat.h from newer kernel (v6.14-rc4).
This is a follow-up for 945a8210c7 and
makes the st_dev check generic, so that we can reuse it some other
places. It also incorporates the non-NULL check now, to be a
comprehensive one-stop solution.
The helper is static inline so that compilers can optimize the redundant
checks away in case it is combined with other checks.
For anonymous inodes, the result would be 0, but
the struct stat is initialized obviously.
So let's switch to st_dev for the check, which
is guaranteed to be non-zero.
Also this is completely unnecessary for statx(),
since we check stx_mask first and that on its own
denotes that the struct is initialized.
When newer glibc is used, but kernel does not support statx(), then
glibc try to fallback with fstatat(). That's quite similar to our
implementation, but the supported flags are different, and if
unsupported flags are specified, it returns EINVAL.
Let's handle the case more gracefully.
Let's be more accurate about what this function does: it checks whether
the underlying reported inode is the same. Internally, this already uses
a better named stat_inode_same() call, hence let's similarly name the
wrapping function following the same logic.
Similar for files_same_at() and path_equal_or_same_files().
No code changes, just some renaming.
Lennart Poettering
Daan De Meyer
Mike Yuan
Yu Watanabe
Lennart Poettering
Zbigniew Jędrzejewski-Szmek
Daan De Meyer