On 28.03.23 11:46, Juergen Gross wrote:
Hello Juergen > scsiback_free_translation_entry() shouldn't be called under spinlock, > as it can sleep. > > This requires to split removing a translation entry from the v2p list > from actually calling kref_put() for the entry. > > Reported-by: Dan Carpenter <[email protected]> > Link: > https://urldefense.com/v3/__https://lore.kernel.org/lkml/Y*JUIl64UDmdkboh@kadam/__;Kw!!GF_29dbcQIUBPA!23IKdVhamoFq8ptUnprd_TubDMObj-0QAalsGiffBHCeEdOuwrq7z4ohg92Sj0olgl0nh73oXvSr-i1zqXhY$ > [lore[.]kernel[.]org] > Signed-off-by: Juergen Gross <[email protected]> > --- > drivers/xen/xen-scsiback.c | 27 ++++++++++++++------------- > 1 file changed, 14 insertions(+), 13 deletions(-) > > diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c > index 954188b0b858..294f29cdc7aa 100644 > --- a/drivers/xen/xen-scsiback.c > +++ b/drivers/xen/xen-scsiback.c > @@ -1010,12 +1010,6 @@ static int scsiback_add_translation_entry(struct > vscsibk_info *info, > return err; > } > > -static void __scsiback_del_translation_entry(struct v2p_entry *entry) > -{ > - list_del(&entry->l); > - kref_put(&entry->kref, scsiback_free_translation_entry); > -} > - > /* > Delete the translation entry specified > */ > @@ -1024,18 +1018,20 @@ static int scsiback_del_translation_entry(struct > vscsibk_info *info, > { > struct v2p_entry *entry; > unsigned long flags; > - int ret = 0; > > spin_lock_irqsave(&info->v2p_lock, flags); > /* Find out the translation entry specified */ > entry = scsiback_chk_translation_entry(info, v); > if (entry) > - __scsiback_del_translation_entry(entry); > - else > - ret = -ENOENT; > + list_del(&entry->l); > > spin_unlock_irqrestore(&info->v2p_lock, flags); > - return ret; > + > + if (!entry) > + return -ENOENT; > + > + kref_put(&entry->kref, scsiback_free_translation_entry); > + return 0; > } > > static void scsiback_do_add_lun(struct vscsibk_info *info, const char > *state, > @@ -1239,14 +1235,19 @@ static void scsiback_release_translation_entry(struct > vscsibk_info *info) > { > struct v2p_entry *entry, *tmp; > struct list_head *head = &(info->v2p_entry_lists); > + struct list_head tmp_list; I would use LIST_HEAD(tmp_list); > unsigned long flags; > > spin_lock_irqsave(&info->v2p_lock, flags); > > - list_for_each_entry_safe(entry, tmp, head, l) > - __scsiback_del_translation_entry(entry); > + list_cut_before(&tmp_list, head, head); so we just move all entries from head to tmp_list here to be processed... > > spin_unlock_irqrestore(&info->v2p_lock, flags); ... when the lock is not held, ok Patch LGTM, but one (maybe stupid) question to clarify. Why do we need to use a lock here in the first place? The scsiback_release_translation_entry() gets called when the driver instance is about to be removed and *after* the disconnection from otherend (so no requests are expected), so what else might cause this list to be accessed concurrently? > + > + list_for_each_entry_safe(entry, tmp, &tmp_list, l) { > + list_del(&entry->l); > + kref_put(&entry->kref, scsiback_free_translation_entry); > + } > } > > static void scsiback_remove(struct xenbus_device *dev)
