From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 6 Mar 2023 11:06:21 +0000 (+0100)
Subject: loop-util: keep track of inode/devnum of backing file
X-Git-Tag: v254-rc1~1072^2~8
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4d2a9e3ea6f1dbfb702abfd5312b1c8c719f4ecf;p=thirdparty%2Fsystemd.git

loop-util: keep track of inode/devnum of backing file
---

diff --git a/src/shared/loop-util.c b/src/shared/loop-util.c
index 6e187efe94b..96a42b41257 100644
--- a/src/shared/loop-util.c
+++ b/src/shared/loop-util.c
@@ -595,6 +595,8 @@ static int loop_device_make_internal(
         }
 
         d->backing_file = TAKE_PTR(backing_file);
+        d->backing_inode = st.st_ino;
+        d->backing_devno = st.st_dev;
 
         log_debug("Successfully acquired %s, devno=%u:%u, nr=%i, diskseq=%" PRIu64,
                   d->node,
@@ -841,11 +843,12 @@ int loop_device_open(
 
         _cleanup_close_ int fd = -EBADF, lock_fd = -EBADF;
         _cleanup_free_ char *node = NULL, *backing_file = NULL;
+        dev_t devnum, backing_devno = 0;
         struct loop_info64 info;
+        ino_t backing_inode = 0;
         uint64_t diskseq = 0;
         LoopDevice *d;
         const char *s;
-        dev_t devnum;
         int r, nr = -1;
 
         assert(dev);
@@ -878,6 +881,9 @@ int loop_device_open(
                         if (!backing_file)
                                 return -ENOMEM;
                 }
+
+                backing_devno = info.lo_device;
+                backing_inode = info.lo_inode;
         }
 
         r = fd_get_diskseq(fd, &diskseq);
@@ -913,6 +919,8 @@ int loop_device_open(
                 .node = TAKE_PTR(node),
                 .dev = sd_device_ref(dev),
                 .backing_file = TAKE_PTR(backing_file),
+                .backing_inode = backing_inode,
+                .backing_devno = backing_devno,
                 .relinquished = true, /* It's not ours, don't try to destroy it when this object is freed */
                 .devno = devnum,
                 .diskseq = diskseq,
diff --git a/src/shared/loop-util.h b/src/shared/loop-util.h
index 5c79ed7ccee..ea461434e9c 100644
--- a/src/shared/loop-util.h
+++ b/src/shared/loop-util.h
@@ -14,12 +14,14 @@ struct LoopDevice {
         unsigned n_ref;
         int fd;
         int lock_fd;
-        int nr;   /* The loopback device index (i.e. 4 for /dev/loop4); if this object encapsulates a non-loopback block device, set to -1 */
-        dev_t devno;
+        int nr;         /* The loopback device index (i.e. 4 for /dev/loop4); if this object encapsulates a non-loopback block device, set to -1 */
+        dev_t devno;    /* The loopback device's own dev_t */
         char *node;
         sd_device *dev;
         char *backing_file;
         bool relinquished;
+        dev_t backing_devno; /* The backing file's dev_t */
+        ino_t backing_inode; /* The backing file's ino_t */
         uint64_t diskseq; /* Block device sequence number, monothonically incremented by the kernel on create/attach, or 0 if we don't know */
         uint64_t uevent_seqnum_not_before; /* uevent sequm right before we attached the loopback device, or UINT64_MAX if we don't know */
         usec_t timestamp_not_before; /* CLOCK_MONOTONIC timestamp taken immediately before attaching the loopback device, or USEC_INFINITY if we don't know */