From: Karel Zak <kzak@redhat.com>
Date: Thu, 28 May 2026 12:01:53 +0000 (+0200)
Subject: fstrim: resolve non-device sources to real block devices
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=310255b275d354a024794fbe37371c74d9c0f096;p=thirdparty%2Futil-linux.git

fstrim: resolve non-device sources to real block devices

When fstrim reads fstab entries (--fstab, --listed-in), bind mount
entries use directory paths as sources (e.g. /data/ssd/ldap) rather
than device names. Source de-duplication compares path strings, so
these never match the real device paths (e.g. /dev/mapper/foo),
causing the same filesystem to be trimmed multiple times.

Use statmount(STATMOUNT_SB_SOURCE) to resolve directory source paths
to their real block device before de-duplication. Fall back to the
original source when statmount() is unavailable.

Addresses: https://github.com/util-linux/util-linux/issues/857
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/sys-utils/fstrim.c b/sys-utils/fstrim.c
index 208e9008e..cd96f77ab 100644
--- a/sys-utils/fstrim.c
+++ b/sys-utils/fstrim.c
@@ -47,6 +47,7 @@
 #include "sysfs.h"
 #include "optutils.h"
 #include "statfs_magic.h"
+#include "mountutils.h"
 
 #include <libmount.h>
 
@@ -368,6 +369,26 @@ static int fstrim_all_from_file(struct fstrim_control *ctl, const char *filename
 			continue;	/* overlaying mount */
 		}
 
+		/* resolve non-device source (e.g. bind mount directory
+		 * path) to real block device via statmount();
+		 * requires mountfd support (mountutils.h) */
+#ifdef STATMOUNT_SB_SOURCE
+		if (is_directory(src, 1)) {
+			char *orig = xstrdup(src);
+
+			mnt_fs_set_source(fs, NULL);
+			src = NULL;
+			if (mnt_fs_fetch_statmount(fs,
+					STATMOUNT_SB_SOURCE) == 0)
+				src = mnt_fs_get_srcpath(fs);
+			if (!src || *src != '/') {
+				mnt_fs_set_source(fs, orig);
+				src = mnt_fs_get_srcpath(fs);
+			}
+			free(orig);
+		}
+#endif
+
 		if (!is_directory(tgt, 1) ||
 		    !has_discard(src, &wholedisk)) {
 			mnt_table_remove_fs(tab, fs);