This is supposed to be a help for compilers to apply optimizations on
functions where they can't determine whether they are const/pure on
their own. For static, local functions the compiler can do this on its
own easily however, hence the decoration with pure/const is just noise.
Let's drop it, and let the compiler to its thing better.
(Use it for exported functions, since compilers can't 'reach-over' into
other modules to determine if they are pure, except if LTO is used)
Previously, in path_is_root_at(), if statx() does not provide mount ID,
path_get_mnt_id_at() was called, but it also calls statx(). Let's avoid
the second trial.
Now, dir_fd_is_root() is heavily used in chaseat(), which is used at
various places. If the kernel is too old and /proc is not mounted, then
there is no way to get the mount ID of a directory. In that case, let's
silently skip the mount ID check.
Fixes https://github.com/systemd/systemd/pull/27299#issuecomment-1511403680.
The /proc/self/fd/ interface cannot be used to follow symlinks pinned
via O_PATH. Add a comment + test for that. Moreover, using fd_reopen()
with O_NOFOLLOW cannot work. Add an explicit check and test for that, to
make behaviour uniform.
-1 was used everywhere, but -EBADF or -EBADFD started being used in various
places. Let's make things consistent in the new style.
Note that there are two candidates:
EBADF 9 Bad file descriptor
EBADFD 77 File descriptor in bad state
Since we're initializating the fd, we're just assigning a value that means
"no fd yet", so it's just a bad file descriptor, and the first errno fits
better. If instead we had a valid file descriptor that became invalid because
of some operation or state change, the other errno would fit better.
In some places, initialization is dropped if unnecessary.
This is a wrapper around fd_reopen() that will reopen an fd if the
F_GETFL flags indicate this is necessary, and otherwise not.
This is useful for various utility calls that shall be able to operate
on O_PATH and without it, and might need to convert between the two
depending on what's passed in.
We have free_and_replace() and friends, they are all named with lower
letters, even they are macros, not functions.
For consistency, let's rename CLOSE_AND_REPLACE() with lower letters.
This also mekes the macro used more places.
Add special case optimization for a single exception fd. It's a
pretty common case in our codebase, and the optimization is simple
and means we don't need to copy/sort the exception array, so do it.
This adds a tiny shortcut to fd_reopen(): if we are about to reopen the
fd via O_DIRECTORY then we know it#s a directory and we might as well
reopen it via opening "." using the fd as "at fd" in openat().
This has the benefit that we don't need /proc/self/fd/ around for this
special case: fewer sources of errors.
Even though it's just a fallback path, let's not be sloppy and allocate in
the crash handler.
> The deadlock happens because systemd crash in malloc() then in signal
> handler, it calls malloc() (close_all_fds()-> opendir()-> __alloc_dir())
> again. malloc() is not a signal-safe function, maybe we should re-think
> the logic here.
Fixes#20266.
We need a sorted list of fds to skip over when closing. We would allocate a
copy of the passed array to do the sort. But all callers construct a temporary
array to pass to us, so it is pointless to copy it again.
close_all_fds/safe_fork_full/namespace_fork/fork_agent are changed to pass
a non-const int array. I checked all users, and all callers are fine with
the array being sorted.
The function was returning some number (sometimes 1, sometimes the extent
of the range passed over to close_range(), ???). Anyway, all callers only
check for error, so let's return 0 on success.
fd_duplicate_data_fd() is renamed to copy_data_fd(). This makes
the two functions have nicely similar names.
Now fd-util.[ch] is again about low-level file descriptor manipulations.
copy_data_fd() is a complex function that internally wraps the other
functions in copy.c. I want to move copy.c and the whole cluster of
related code from basic/ to shared/ later on, and this is a preparatory
step for that.
Zbigniew Jędrzejewski-Szmek
Lennart Poettering
Yu Watanabe
Daan De Meyer
David Tardon
Thomas Haller
Rudi Heitbaum
Susant Sahani