shared: add new wrapper for online fs resizing ioctls

src/shared/meson.build

@@ -147,6 +147,8 @@ shared_sources = files('''
         ptyfwd.h
         reboot-util.c
         reboot-util.h
+        resize-fs.c
+        resize-fs.h
         resolve-util.c
         resolve-util.h
         seccomp-util.h

src/shared/resize-fs.c

@@ -0,0 +1,112 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <linux/btrfs.h>
+#include <linux/magic.h>
+#include <sys/ioctl.h>
+#include <sys/vfs.h>
+
+#include "blockdev-util.h"
+#include "fs-util.h"
+#include "missing_fs.h"
+#include "missing_magic.h"
+#include "missing_xfs.h"
+#include "resize-fs.h"
+#include "stat-util.h"
+
+int resize_fs(int fd, uint64_t sz) {
+        struct statfs sfs;
+        int r;
+
+        assert(fd >= 0);
+
+        /* Rounds down to next block size */
+
+        if (sz <= 0 || sz == UINT64_MAX)
+                return -ERANGE;
+
+        if (fstatfs(fd, &sfs) < 0)
+                return -errno;
+
+        if (is_fs_type(&sfs, EXT4_SUPER_MAGIC)) {
+                uint64_t u;
+
+                if (sz < EXT4_MINIMAL_SIZE)
+                        return -ERANGE;
+
+                u = sz / sfs.f_bsize;
+
+                if (ioctl(fd, EXT4_IOC_RESIZE_FS, &u) < 0)
+                        return -errno;
+
+        } else if (is_fs_type(&sfs, BTRFS_SUPER_MAGIC)) {
+                struct btrfs_ioctl_vol_args args = {};
+
+                /* 256M is the minimize size enforced by the btrfs kernel code when resizing (which is
+                 * strange btw, as mkfs.btrfs is fine creating file systems > 109M). It will return EINVAL in
+                 * that case, let's catch this error beforehand though, and report a more explanatory
+                 * error. */
+
+                if (sz < BTRFS_MINIMAL_SIZE)
+                        return -ERANGE;
+
+                r = snprintf(args.name, sizeof(args.name), "%" PRIu64, sz);
+                assert((size_t) r < sizeof(args.name));
+
+                if (ioctl(fd, BTRFS_IOC_RESIZE, &args) < 0)
+                        return -errno;
+
+        } else if (is_fs_type(&sfs, XFS_SB_MAGIC)) {
+                xfs_fsop_geom_t geo;
+                xfs_growfs_data_t d;
+
+                if (sz < XFS_MINIMAL_SIZE)
+                        return -ERANGE;
+
+                if (ioctl(fd, XFS_IOC_FSGEOMETRY, &geo) < 0)
+                        return -errno;
+
+                d = (xfs_growfs_data_t) {
+                        .imaxpct = geo.imaxpct,
+                        .newblocks = sz / geo.blocksize,
+                };
+
+                if (ioctl(fd, XFS_IOC_FSGROWFSDATA, &d) < 0)
+                        return -errno;
+
+        } else
+                return -EOPNOTSUPP;
+
+        return 0;
+}
+
+uint64_t minimal_size_by_fs_magic(statfs_f_type_t magic) {
+
+        switch (magic) {
+
+        case (statfs_f_type_t) EXT4_SUPER_MAGIC:
+                return EXT4_MINIMAL_SIZE;
+
+        case (statfs_f_type_t) XFS_SB_MAGIC:
+                return XFS_MINIMAL_SIZE;
+
+        case (statfs_f_type_t) BTRFS_SUPER_MAGIC:
+                return  BTRFS_MINIMAL_SIZE;
+
+        default:
+                return UINT64_MAX;
+        }
+}
+
+uint64_t minimal_size_by_fs_name(const char *name) {
+
+        if (streq_ptr(name, "ext4"))
+                return EXT4_MINIMAL_SIZE;
+
+        if (streq_ptr(name, "xfs"))
+                return XFS_MINIMAL_SIZE;
+
+        if (streq_ptr(name, "btrfs"))
+                return BTRFS_MINIMAL_SIZE;
+
+        return UINT64_MAX;
+}

src/shared/resize-fs.h

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+#include <inttypes.h>
+
+#include "stat-util.h"
+
+int resize_fs(int fd, uint64_t sz);
+
+#define BTRFS_MINIMAL_SIZE (256U*1024U*1024U)
+#define XFS_MINIMAL_SIZE (14U*1024U*1024U)
+#define EXT4_MINIMAL_SIZE (1024U*1024U)
+
+uint64_t minimal_size_by_fs_magic(statfs_f_type_t magic);
+uint64_t minimal_size_by_fs_name(const char *str);