Patch "afs: Fix cell purging with aliases" has been added to the 5.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    afs: Fix cell purging with aliases

to the 5.8-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:
     afs-fix-cell-purging-with-aliases.patch
and it can be found in the queue-5.8 subdirectory.

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



commit 4d82b0fcb551c9685b3b4a7f71f08857eb9e2f6c
Author: David Howells <dhowells@xxxxxxxxxx>
Date:   Thu Oct 15 11:05:01 2020 +0100

    afs: Fix cell purging with aliases
    
    [ Upstream commit 286377f6bdf71568a4cf07104fe44006ae0dba6d ]
    
    When the afs module is removed, one of the things that has to be done is to
    purge the cell database.  afs_cell_purge() cancels the management timer and
    then starts the cell manager work item to do the purging.  This does a
    single run through and then assumes that all cells are now purged - but
    this is no longer the case.
    
    With the introduction of alias detection, a later cell in the database can
    now be holding an active count on an earlier cell (cell->alias_of).  The
    purge scan passes by the earlier cell first, but this can't be got rid of
    until it has discarded the alias.  Ordinarily, afs_unuse_cell() would
    handle this by setting the management timer to trigger another pass - but
    afs_set_cell_timer() doesn't do anything if the namespace is being removed
    (net->live == false).  rmmod then hangs in the wait on cells_outstanding in
    afs_cell_purge().
    
    Fix this by making afs_set_cell_timer() directly queue the cell manager if
    net->live is false.  This causes additional management passes.
    
    Queueing the cell manager increments cells_outstanding to make sure the
    wait won't complete until all cells are destroyed.
    
    Fixes: 8a070a964877 ("afs: Detect cell aliases 1 - Cells with root volumes")
    Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index c906000b0ff84..1944be78e9b0d 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -19,6 +19,7 @@ static unsigned __read_mostly afs_cell_gc_delay = 10;
 static unsigned __read_mostly afs_cell_min_ttl = 10 * 60;
 static unsigned __read_mostly afs_cell_max_ttl = 24 * 60 * 60;
 
+static void afs_queue_cell_manager(struct afs_net *);
 static void afs_manage_cell_work(struct work_struct *);
 
 static void afs_dec_cells_outstanding(struct afs_net *net)
@@ -37,6 +38,8 @@ static void afs_set_cell_timer(struct afs_net *net, time64_t delay)
 		atomic_inc(&net->cells_outstanding);
 		if (timer_reduce(&net->cells_timer, jiffies + delay * HZ))
 			afs_dec_cells_outstanding(net);
+	} else {
+		afs_queue_cell_manager(net);
 	}
 }