From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59C722E093A; Sat, 21 Mar 2026 11:55:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774094155; cv=none; b=sTXajewce+Lx7MIzo+M8ajzJ8EzINKDyig8EUbb/oqTWmxujyzBTN+KEW5iY7ZC/MNpFK+/h5KaMl2TX9CjQHxnzHOdTsbTrzNGsDvLd/t4nyPzgI8KoC00lR0/CCZ7k0iMPmJnv1X8hiQ7wHHBmkPSC2auhMgWDAFMd+USbIfs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774094155; c=relaxed/simple; bh=lvL4EldL7WqBWOKOgCGDgpa+YxAUJE4h3UjLrMVTpOA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MEgK+PjB63BI/ZcDR397zzxLLxQSgdWX/9lcLo/YOJNdz8LTfHcwYnDMxDw9/DFL68roPsiijP1im9DK9253erah/g74KzQ9+fgKKIn4RR8w0yHWjaNpLCAoHh4+zKiy0pQl6wgMgzw3my4SjRTe+uSMQg86JkgZ+jo4fh+hT2M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=c2yrSjrp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="c2yrSjrp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED8C1C19421; Sat, 21 Mar 2026 11:55:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774094155; bh=lvL4EldL7WqBWOKOgCGDgpa+YxAUJE4h3UjLrMVTpOA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c2yrSjrp61VwPbFklVWnVv4dmwlkLmW3i8Y5VW2WU1eJozYguU3uALnpaysX6hqxH GBD4LgM9ku6WrcJHAXkYVfQ9OsnihBe8/KOFZoSDS8oUfF77Emt60WrtiIpswELE4c IvCxqGAGmlIageL3sic7he13DGOgh5WzqhgSoZ5qMC2mPzBUl5W9R1yoUJNZAxy+W+ w6L4qns8RY9iE6u/GAGBJiwK9ZNvktz9ZzWly0vMTnm0RBDUkdi0pqS+gdCtq5GSXf cSAA3tSpYr1ujfdcD3y8PQ79vogZOcnPKZYzzhICU0DbtgqvFMfFhPhaojVTw0Pmk/ T70XTeifx32+A== From: Anand Jain To: linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org Cc: linux-xfs@vger.kernel.org, hch@infradead.org Subject: [PATCH v2 3/3] ext4: derive f_fsid from block device to avoid collisions Date: Sat, 21 Mar 2026 19:55:19 +0800 Message-ID: <33e8eb64c304a4d42b60f608c26497bf9a2e9e19.1774092915.git.asj@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit statfs() currently reports f_fsid derived from the on-disk UUID. Cloned block devices share the same UUID, so distinct ext4 instances can return identical f_fsid values. This leads to collisions in fanotify. Encode sb->s_dev into f_fsid instead of using the superblock UUID. This provides a per-device identifier and avoids conflicts when filesystem is cloned, matching the behavior with xfs. Place this change behind the new mount option "-o nouuid" for ABI compatibility. Signed-off-by: Anand Jain --- fs/ext4/ext4.h | 1 + fs/ext4/super.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 293f698b7042..64d98ab64c11 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1282,6 +1282,7 @@ struct ext4_inode_info { * scanning in mballoc */ #define EXT4_MOUNT2_ABORT 0x00000100 /* Abort filesystem */ +#define EXT4_MOUNT2_NOUUID 0x00000200 /* No duplicate f_fsid for cloned filesystem */ #define clear_opt(sb, opt) EXT4_SB(sb)->s_mount_opt &= \ ~EXT4_MOUNT_##opt diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 43f680c750ae..65b712af4ad7 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1664,7 +1664,7 @@ static const struct export_operations ext4_export_ops = { enum { Opt_bsd_df, Opt_minix_df, Opt_grpid, Opt_nogrpid, Opt_resgid, Opt_resuid, Opt_sb, - Opt_nouid32, Opt_debug, Opt_removed, + Opt_nouid32, Opt_debug, Opt_removed, Opt_nouuid, Opt_user_xattr, Opt_acl, Opt_auto_da_alloc, Opt_noauto_da_alloc, Opt_noload, Opt_commit, Opt_min_batch_time, Opt_max_batch_time, Opt_journal_dev, @@ -1743,6 +1743,7 @@ static const struct fs_parameter_spec ext4_param_specs[] = { fsparam_u32 ("sb", Opt_sb), fsparam_enum ("errors", Opt_errors, ext4_param_errors), fsparam_flag ("nouid32", Opt_nouid32), + fsparam_flag ("nouuid", Opt_nouuid), fsparam_flag ("debug", Opt_debug), fsparam_flag ("oldalloc", Opt_removed), fsparam_flag ("orlov", Opt_removed), @@ -1898,6 +1899,7 @@ static const struct mount_opts { {Opt_acl, 0, MOPT_NOSUPPORT}, #endif {Opt_nouid32, EXT4_MOUNT_NO_UID32, MOPT_SET}, + {Opt_nouuid, EXT4_MOUNT2_NOUUID, MOPT_SET | MOPT_2}, {Opt_debug, EXT4_MOUNT_DEBUG, MOPT_SET}, {Opt_quota, EXT4_MOUNT_QUOTA | EXT4_MOUNT_USRQUOTA, MOPT_SET | MOPT_Q}, {Opt_usrquota, EXT4_MOUNT_QUOTA | EXT4_MOUNT_USRQUOTA, @@ -2389,6 +2391,9 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param) return -EINVAL; } return 0; + case Opt_nouuid: + ctx_set_mount_opt2(ctx, EXT4_MOUNT2_NOUUID); + return 0; } /* @@ -6941,7 +6946,10 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf) buf->f_files = le32_to_cpu(es->s_inodes_count); buf->f_ffree = percpu_counter_sum_positive(&sbi->s_freeinodes_counter); buf->f_namelen = EXT4_NAME_LEN; - buf->f_fsid = uuid_to_fsid(es->s_uuid); + if (test_opt2(sb, NOUUID)) + buf->f_fsid = u64_to_fsid(huge_encode_dev(sb->s_bdev->bd_dev)); + else + buf->f_fsid = uuid_to_fsid(es->s_uuid); #ifdef CONFIG_QUOTA if (ext4_test_inode_flag(dentry->d_inode, EXT4_INODE_PROJINHERIT) && -- 2.43.0