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From 81f0a57bed6e03eeaa24443d16555c7f5d20ee1a Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Wed, 22 Apr 2015 13:08:19 +0200
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Subject: [PATCH] btrfs-util: introduce btrfs_is_filesystem() and make use of
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 it where appropriate
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Let's unify the code that checks whether an fd is on btrfs a bit.
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(Also, rename btrfs_is_snapshot() to btrfs_is_subvol(), since that's
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usually how this is referred to in our code)
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(cherry picked from commit 21222ea5cdec65fa30a75bd5a78475459075b946)
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Related: #1299714
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---
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 src/shared/btrfs-util.c    | 23 ++++++++++++++++-------
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 src/shared/btrfs-util.h    |  3 ++-
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 src/shared/machine-image.c |  9 ++++-----
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 3 files changed, 22 insertions(+), 13 deletions(-)
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diff --git a/src/shared/btrfs-util.c b/src/shared/btrfs-util.c
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index b34ac8b15..52a214349 100644
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--- a/src/shared/btrfs-util.c
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+++ b/src/shared/btrfs-util.c
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@@ -83,10 +83,22 @@ static int extract_subvolume_name(const char *path, const char **subvolume) {
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         return 0;
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 }
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-int btrfs_is_snapshot(int fd) {
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-        struct stat st;
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+int btrfs_is_filesystem(int fd) {
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         struct statfs sfs;
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+        assert(fd >= 0);
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+
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+        if (fstatfs(fd, &sfs) < 0)
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+                return -errno;
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+
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+        return F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC);
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+}
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+
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+int btrfs_is_subvol(int fd) {
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+        struct stat st;
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+
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+        assert(fd >= 0);
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+
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         /* On btrfs subvolumes always have the inode 256 */
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         if (fstat(fd, &st) < 0)
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@@ -95,10 +107,7 @@ int btrfs_is_snapshot(int fd) {
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         if (!S_ISDIR(st.st_mode) || st.st_ino != 256)
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                 return 0;
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-        if (fstatfs(fd, &sfs) < 0)
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-                return -errno;
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-
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-        return F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC);
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+        return btrfs_is_filesystem(fd);
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 }
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 int btrfs_subvol_snapshot(const char *old_path, const char *new_path, bool read_only, bool fallback_copy) {
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@@ -115,7 +124,7 @@ int btrfs_subvol_snapshot(const char *old_path, const char *new_path, bool read_
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         if (old_fd < 0)
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                 return -errno;
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-        r = btrfs_is_snapshot(old_fd);
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+        r = btrfs_is_subvol(old_fd);
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         if (r < 0)
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                 return r;
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         if (r == 0) {
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diff --git a/src/shared/btrfs-util.h b/src/shared/btrfs-util.h
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index 1b9c142e5..1315def87 100644
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--- a/src/shared/btrfs-util.h
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+++ b/src/shared/btrfs-util.h
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@@ -43,7 +43,8 @@ typedef struct BtrfsQuotaInfo {
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         uint64_t exclusive_max;
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 } BtrfsQuotaInfo;
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-int btrfs_is_snapshot(int fd);
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+int btrfs_is_filesystem(int fd);
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+int btrfs_is_subvol(int fd);
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 int btrfs_subvol_make(const char *path);
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 int btrfs_subvol_make_label(const char *path);
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diff --git a/src/shared/machine-image.c b/src/shared/machine-image.c
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index c02ee814c..256622928 100644
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--- a/src/shared/machine-image.c
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+++ b/src/shared/machine-image.c
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@@ -136,12 +136,11 @@ static int image_make(
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                 /* btrfs subvolumes have inode 256 */
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                 if (st.st_ino == 256) {
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-                        struct statfs sfs;
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-                        if (fstatfs(fd, &sfs) < 0)
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-                                return -errno;
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-
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-                        if (F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC)) {
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+                        r = btrfs_is_filesystem(fd);
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+                        if (r < 0)
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+                                return r;
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+                        if (r) {
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                                 BtrfsSubvolInfo info;
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                                 BtrfsQuotaInfo quota;
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