Patch "cifs: Fix df output for users with quota limits" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

cifs: Fix df output for users with quota limits

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cifs-fix-df-output-for-users-with-quota-limits.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sachin Prabhu <[email protected]>
Date: Thu, 3 Aug 2017 13:09:03 +0530
Subject: cifs: Fix df output for users with quota limits

From: Sachin Prabhu <[email protected]>

commit 42bec214d8bd432be6d32a1acb0a9079ecd4d142 upstream.

The df for a SMB2 share triggers a GetInfo call for FS_FULL_SIZE_INFORMATION. The values returned are used to populate struct statfs.

The problem is that none of the information returned by the call contains the total blocks available on the filesystem. Instead we use the blocks available to the user ie. quota limitation when filling out statfs.f_blocks. The information returned does contain Actual free units on the filesystem and is used to populate statfs.f_bfree. For users with quota enabled, it can lead to situations where the total free space reported is more than the total blocks on the system ending up with df reports like the following

 # df -h /mnt/a
Filesystem         Size  Used Avail Use% Mounted on
//192.168.22.10/a  2.5G -2.3G  2.5G    - /mnt/a

To fix this problem, we instead populate both statfs.f_bfree with the same value as statfs.f_bavail ie. CallerAvailableAllocationUnits. This is similar to what is done already in the code for cifs and df now reports the quota information for the user used to mount the share.

 # df --si /mnt/a
Filesystem         Size  Used Avail Use% Mounted on
//192.168.22.10/a  2.7G  101M  2.6G   4% /mnt/a

---
 fs/cifs/smb2pdu.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -2768,8 +2768,8 @@ copy_fs_info_to_kstatfs(struct smb2_fs_f
 	kst->f_bsize = le32_to_cpu(pfs_inf->BytesPerSector) *
 			  le32_to_cpu(pfs_inf->SectorsPerAllocationUnit);
 	kst->f_blocks = le64_to_cpu(pfs_inf->TotalAllocationUnits);
-	kst->f_bfree  = le64_to_cpu(pfs_inf->ActualAvailableAllocationUnits);
-	kst->f_bavail = le64_to_cpu(pfs_inf->CallerAvailableAllocationUnits);
+	kst->f_bfree  = kst->f_bavail =
+			le64_to_cpu(pfs_inf->CallerAvailableAllocationUnits);
 	return;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/cifs-fix-df-output-for-users-with-quota-limits.patch