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From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 26 Feb 2021 17:39:55 +0100
Subject: btrfs-util: add helper that abstracts "might be btrfs subvol?" check
Let#s not hardcode inode nr 256 everywhere, but abstract this check
slightly.
(cherry picked from commit 674b04ff1b6deab17f5d36c036c0275ba94e1ebc)
(cherry picked from commit 190c6bcfc3518bec964ab740085ac88ccc86dcc7)
---
src/basic/btrfs-util.c | 6 +++---
src/basic/btrfs-util.h | 10 ++++++++++
src/basic/rm-rf.c | 2 +-
src/import/export-tar.c | 2 +-
src/shared/machine-image.c | 3 +--
5 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/src/basic/btrfs-util.c b/src/basic/btrfs-util.c
index 2634659..f0df51a 100644
--- a/src/basic/btrfs-util.c
+++ b/src/basic/btrfs-util.c
@@ -91,7 +91,7 @@ int btrfs_is_subvol_fd(int fd) {
if (fstat(fd, &st) < 0)
return -errno;
- if (!S_ISDIR(st.st_mode) || st.st_ino != 256)
+ if (!btrfs_might_be_subvol(&st))
return 0;
return btrfs_is_filesystem(fd);
@@ -194,7 +194,7 @@ int btrfs_subvol_set_read_only_fd(int fd, bool b) {
if (fstat(fd, &st) < 0)
return -errno;
- if (!S_ISDIR(st.st_mode) || st.st_ino != 256)
+ if (!btrfs_might_be_subvol(&st))
return -EINVAL;
if (ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags) < 0)
@@ -229,7 +229,7 @@ int btrfs_subvol_get_read_only_fd(int fd) {
if (fstat(fd, &st) < 0)
return -errno;
- if (!S_ISDIR(st.st_mode) || st.st_ino != 256)
+ if (!btrfs_might_be_subvol(&st))
return -EINVAL;
if (ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags) < 0)
diff --git a/src/basic/btrfs-util.h b/src/basic/btrfs-util.h
index c8b44f6..0f569b6 100644
--- a/src/basic/btrfs-util.h
+++ b/src/basic/btrfs-util.h
@@ -127,3 +127,13 @@ static inline int btrfs_log_dev_root(int level, int ret, const char *p) {
"File system behind %s is reported by btrfs to be backed by pseudo-device /dev/root, which is not a valid userspace accessible device node. "
"Cannot determine correct backing block device.", p);
}
+
+static inline bool btrfs_might_be_subvol(const struct stat *st) {
+ if (!st)
+ return false;
+
+ /* Returns true if this 'struct stat' looks like it could refer to a btrfs subvolume. To make a final
+ * decision, needs to be combined with an fstatfs() check to see if this is actually btrfs. */
+
+ return S_ISDIR(st->st_mode) && st->st_ino == 256;
+}
diff --git a/src/basic/rm-rf.c b/src/basic/rm-rf.c
index b0d682f..4c39ce8 100644
--- a/src/basic/rm-rf.c
+++ b/src/basic/rm-rf.c
@@ -147,7 +147,7 @@ int rm_rf_children(int fd, RemoveFlags flags, struct stat *root_dev) {
if (r > 0)
continue;
- if ((flags & REMOVE_SUBVOLUME) && st.st_ino == 256) {
+ if ((flags & REMOVE_SUBVOLUME) && btrfs_might_be_subvol(&st)) {
/* This could be a subvolume, try to remove it */
diff --git a/src/import/export-tar.c b/src/import/export-tar.c
index b8b650f..1e6b2c1 100644
--- a/src/import/export-tar.c
+++ b/src/import/export-tar.c
@@ -283,7 +283,7 @@ int tar_export_start(TarExport *e, const char *path, int fd, ImportCompressType
e->quota_referenced = (uint64_t) -1;
- if (e->st.st_ino == 256) { /* might be a btrfs subvolume? */
+ if (btrfs_might_be_subvol(&e->st)) {
BtrfsQuotaInfo q;
r = btrfs_subvol_get_subtree_quota_fd(sfd, 0, &q);
diff --git a/src/shared/machine-image.c b/src/shared/machine-image.c
index 671a56b..c7cf5e9 100644
--- a/src/shared/machine-image.c
+++ b/src/shared/machine-image.c
@@ -248,8 +248,7 @@ static int image_make(
if (fd < 0)
return -errno;
- /* btrfs subvolumes have inode 256 */
- if (st->st_ino == 256) {
+ if (btrfs_might_be_subvol(st)) {
r = btrfs_is_filesystem(fd);
if (r < 0)
|
