FAILED: patch "[PATCH] xfs: don't over-report free space or inodes in statvfs" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 4b8d867ca6e2fc6d152f629fdaf027053b81765a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025020409-refurbish-stereo-db71@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4b8d867ca6e2fc6d152f629fdaf027053b81765a Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <[email protected]>
Date: Thu, 12 Dec 2024 14:37:56 -0800
Subject: [PATCH] xfs: don't over-report free space or inodes in statvfs

Emmanual Florac reports a strange occurrence when project quota limits are enabled, free space is lower than the remaining quota, and someone runs statvfs:

  # mkfs.xfs -f /dev/sda
  # mount /dev/sda /mnt -o prjquota
  # xfs_quota  -x -c 'limit -p bhard=2G 55' /mnt
  # mkdir /mnt/dir
  # xfs_io -c 'chproj 55' -c 'chattr +P' -c 'stat -vvvv' /mnt/dir
  # fallocate -l 19g /mnt/a
  # df /mnt /mnt/dir
  Filesystem      Size  Used Avail Use% Mounted on
  /dev/sda         20G   20G  345M  99% /mnt
  /dev/sda        2.0G     0  2.0G   0% /mnt

I think the bug here is that xfs_fill_statvfs_from_dquot unconditionally assigns to f_bfree without checking that the filesystem has enough free space to fill the remaining project quota. However, this is a longstanding behavior of xfs so it's unclear what to do here.

index 847ba29630e9..db5b8afd9d1b 100644
@@ -32,21 +32,28 @@ xfs_fill_statvfs_from_dquot(
 	limit = blkres->softlimit ?
 		blkres->softlimit :
 		blkres->hardlimit;
-	if (limit && statp->f_blocks > limit) {
-		statp->f_blocks = limit;
-		statp->f_bfree = statp->f_bavail =
-			(statp->f_blocks > blkres->reserved) ?
-			 (statp->f_blocks - blkres->reserved) : 0;
+	if (limit) {
+		uint64_t	remaining = 0;
+
+		if (limit > blkres->reserved)
+			remaining = limit - blkres->reserved;
+
+		statp->f_blocks = min(statp->f_blocks, limit);
+		statp->f_bfree = min(statp->f_bfree, remaining);
+		statp->f_bavail = min(statp->f_bavail, remaining);
 	}
 
 	limit = dqp->q_ino.softlimit ?
 		dqp->q_ino.softlimit :
 		dqp->q_ino.hardlimit;
-	if (limit && statp->f_files > limit) {
-		statp->f_files = limit;
-		statp->f_ffree =
-			(statp->f_files > dqp->q_ino.reserved) ?
-			 (statp->f_files - dqp->q_ino.reserved) : 0;
+	if (limit) {
+		uint64_t	remaining = 0;
+
+		if (limit > dqp->q_ino.reserved)
+			remaining = limit - dqp->q_ino.reserved;
+
+		statp->f_files = min(statp->f_files, limit);
+		statp->f_ffree = min(statp->f_ffree, remaining);
 	}
 }