After the previous refactoring, we are able to link the daemon to
common/utils, and also remove some of the "duplicate" functions that
the daemon carried ("duplicate" in quotes because they were often not
exact duplicates).
Also this removes the duplicate reimplementation of (most) cleanup
functions in the daemon, since those are provided by libutils now.
It also allows us in future (but not in this commit) to move utility
functions from the daemon into libutils.
The existing APIs guestfs_stat, guestfs_lstat and guestfs_lstatlist
return a stat structure that contains atime, mtime and ctime fields
that store only the timestamp in seconds.
Modern filesystems can store timestamps down to nanosecond
granularity, and the ordinary glibc stat(2) wrapper will return these
in "hidden" stat fields:
struct timespec st_atim; /* Time of last access. */
struct timespec st_mtim; /* Time of last modification. */
struct timespec st_ctim; /* Time of last status change. */
with the following macros defined for backwards compatibility:
#define st_atime st_atim.tv_sec
#define st_mtime st_mtim.tv_sec
#define st_ctime st_ctim.tv_sec
It is not possible to redefine guestfs_stat to return a longer struct
guestfs_stat with room for the extra nanosecond fields, because that
would break the ABI of guestfs_lstatlist as it returns an array
containing consecutive stat structs (not pointers). Changing the
return type of guestfs_stat would break API. Changing the generator
to support symbol versioning is judged to be too intrusive.
Therefore this adds a new struct (guestfs_statns) and new APIs:
guestfs_statns
guestfs_lstatns
guestfs_lstatnslist
which return the new struct (or array of structs in the last case).
The old APIs may of course still be used, forever, but are deprecated
and shouldn't be used in new programs.
Because virt tools are compiled with -DGUESTFS_WARN_DEPRECATED=1, I
have updated all the places calling the deprecated functions. This
has revealed some areas for improvement: in particular virt-diff and
virt-ls could be changed to print the nanosecond fields.
FUSE now returns nanoseconds in stat calls where available, fixing
https://bugzilla.redhat.com/show_bug.cgi?id=1144891
Notes about the implementation:
- guestfs_internal_lstatlist has been removed and replaced by
guestfs_internal_lstatnslist. As the former was an internal API no
one should have been calling it, or indeed can call it unless they
start defining their own header files.
- guestfs_stat and guestfs_lstat have been changed into library-side
functions. They, along with guestfs_lstatlist, are now implemented
as wrappers around the new functions which just throw away the
nanosecond fields.
The presumption is that all file descriptors should be created with
the close-on-exec flag set. The only exception are file descriptors
that we want passed through to exec'd subprocesses (mainly pipes and
stdin/stdout/stderr).
For open calls, we pass O_CLOEXEC as an extra flag, eg:
fd = open ("foo", O_RDONLY|O_CLOEXEC);
This is a Linux-ism, but using a macro we can easily make it portable.
For sockets, similarly:
sock = socket (..., SOCK_STREAM|SOCK_CLOEXEC, ...);
For accepted sockets, we use the Linux accept4 system call which
allows flags to be supplied, but we use the Gnulib 'accept4' module to
make this portable.
For dup, dup2, we use the Linux dup3 system call, and the Gnulib
modules 'dup3' and 'cloexec'.
The RPC stubs already prefix the command name to error messages.
The daemon doesn't have to do this. As a (small) benefit this also
makes the daemon slightly smaller.
Code in the daemon such as:
if (argv[0] == NULL) {
reply_with_error ("passed an empty list");
return NULL;
}
now results in error messages like this:
><fs> command ""
libguestfs: error: command: passed an empty list
(whereas previously you would have seen ..command: command:..)
inotify: Make this optional on platforms that don't have this interface.
mknod, mkfifo etc.: Make these optional on non-Unix platforms.
readdir: If d_type field is missing on the platform, set the corresponding
field to 'u'.
stat: st_blocks and st_blksize are missing on non-Unix platforms, so
set these fields to -1 in the corresponding structures.
These three functions are very specifically designed for FUSE
support, so we can list directories efficiently. Instead of
making lots of lstat, lgetxattr and readlink calls, we can make just
three calls per directory to grab all the attributes (which we
then cache briefly).
Nearly every file-related function in daemons/*.c is affected:
Remove this pair of statements from each affected do_* function:
- NEED_ROOT (return -1);
- ABS_PATH (dir, return -1);
and change the type of the corresponding parameter to "const char *".
* src/generator.ml: Emit NEED_ROOT just once, even when there are two or
more Pathname args.
