diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2023-11-30 12:56:06 +0100 |
|---|---|---|
| committer | David Howells <dhowells@redhat.com> | 2023-12-24 15:22:47 +0000 |
| commit | 4121b4337146b64560d1e46ebec77196d9287802 (patch) | |
| tree | 04cf3050db102dc438e917dcb6859c655e9a9d5f /fs/afs/callback.c | |
| parent | 2daa6404fd2f00985d5bfeb3c161f4630b46b6bf (diff) | |
afs: fix the usage of read_seqbegin_or_lock() in afs_lookup_volume_rcu()
David Howells says:
(2) afs_lookup_volume_rcu().
There can be a lot of volumes known by a system. A thousand would
require a 10-step walk and this is drivable by remote operation, so I
think this should probably take a lock on the second pass too.
Make the "seq" counter odd on the 2nd pass, otherwise read_seqbegin_or_lock()
never takes the lock.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20231130115606.GA21571@redhat.com/
Diffstat (limited to 'fs/afs/callback.c')
| -rw-r--r-- | fs/afs/callback.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/afs/callback.c b/fs/afs/callback.c index a484fa642808..90f9b2a46ff4 100644 --- a/fs/afs/callback.c +++ b/fs/afs/callback.c @@ -110,13 +110,14 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell, { struct afs_volume *volume = NULL; struct rb_node *p; - int seq = 0; + int seq = 1; do { /* Unfortunately, rbtree walking doesn't give reliable results * under just the RCU read lock, so we have to check for * changes. */ + seq++; /* 2 on the 1st/lockless path, otherwise odd */ read_seqbegin_or_lock(&cell->volume_lock, &seq); p = rcu_dereference_raw(cell->volumes.rb_node); |