Patch "xfs: don't free rt blocks when we're doing a REMAP bunmapi call" has been added to the 5.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    xfs: don't free rt blocks when we're doing a REMAP bunmapi call

to the 5.9-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:
     xfs-don-t-free-rt-blocks-when-we-re-doing-a-remap-bu.patch
and it can be found in the queue-5.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 16b172d053828ced1ac37b32dcb94f25ab9c1d5b
Author: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Date:   Mon Sep 21 09:15:08 2020 -0700

    xfs: don't free rt blocks when we're doing a REMAP bunmapi call
    
    [ Upstream commit 8df0fa39bdd86ca81a8d706a6ed9d33cc65ca625 ]
    
    When callers pass XFS_BMAPI_REMAP into xfs_bunmapi, they want the extent
    to be unmapped from the given file fork without the extent being freed.
    We do this for non-rt files, but we forgot to do this for realtime
    files.  So far this isn't a big deal since nobody makes a bunmapi call
    to a rt file with the REMAP flag set, but don't leave a logic bomb.
    
    Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 1b0a01b06a05d..d9a692484eaed 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5046,20 +5046,25 @@ xfs_bmap_del_extent_real(
 
 	flags = XFS_ILOG_CORE;
 	if (whichfork == XFS_DATA_FORK && XFS_IS_REALTIME_INODE(ip)) {
-		xfs_fsblock_t	bno;
 		xfs_filblks_t	len;
 		xfs_extlen_t	mod;
 
-		bno = div_u64_rem(del->br_startblock, mp->m_sb.sb_rextsize,
-				  &mod);
-		ASSERT(mod == 0);
 		len = div_u64_rem(del->br_blockcount, mp->m_sb.sb_rextsize,
 				  &mod);
 		ASSERT(mod == 0);
 
-		error = xfs_rtfree_extent(tp, bno, (xfs_extlen_t)len);
-		if (error)
-			goto done;
+		if (!(bflags & XFS_BMAPI_REMAP)) {
+			xfs_fsblock_t	bno;
+
+			bno = div_u64_rem(del->br_startblock,
+					mp->m_sb.sb_rextsize, &mod);
+			ASSERT(mod == 0);
+
+			error = xfs_rtfree_extent(tp, bno, (xfs_extlen_t)len);
+			if (error)
+				goto done;
+		}
+
 		do_fx = 0;
 		nblks = len * mp->m_sb.sb_rextsize;
 		qfield = XFS_TRANS_DQ_RTBCOUNT;