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target: Fix ALUA transition state race between multiple initiators

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Multiple threads could be writing to alua_access_state at
the same time, or there could be multiple STPGs in flight
(different initiators sending them or one initiator sending
them to different ports), or a combo of both and the
core_alua_do_transition_tg_pt calls will race with each other.

Because from the last patches we no longer delay running
core_alua_do_transition_tg_pt_work, there does not seem to be
any point in running that in a workqueue. And, we always
wait for it to complete one way or another, so we can sleep
in this code path. So, this patch made over target-pending just adds a
mutex and does the work core_alua_do_transition_tg_pt_work was doing in
core_alua_do_transition_tg_pt.

There is also no need to use an atomic for the
tg_pt_gp_alua_access_state. In core_alua_do_transition_tg_pt we will
test and set it under the transition mutex. And, it is a int/32 bits
so in the other places where it is read, we will never see it partially
updated.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Mike Christie
2017-03-29 00:19:24 -05:00
committed by Nicholas Bellinger
parent 7a56dc8888
commit d19c4643a5
3 changed files with 60 additions and 104 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/target/target_core_base.h
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@@ -280,8 +280,6 @@ struct t10_alua_tg_pt_gp {
u16 tg_pt_gp_id;
int tg_pt_gp_valid_id;
int tg_pt_gp_alua_supported_states;
int tg_pt_gp_alua_pending_state;
int tg_pt_gp_alua_previous_state;
int tg_pt_gp_alua_access_status;
int tg_pt_gp_alua_access_type;
int tg_pt_gp_nonop_delay_msecs;
@@ -290,18 +288,16 @@ struct t10_alua_tg_pt_gp {
int tg_pt_gp_pref;
int tg_pt_gp_write_metadata;
u32 tg_pt_gp_members;
atomic_t tg_pt_gp_alua_access_state;
int tg_pt_gp_alua_access_state;
atomic_t tg_pt_gp_ref_cnt;
spinlock_t tg_pt_gp_lock;
struct mutex tg_pt_gp_md_mutex;
struct mutex tg_pt_gp_transition_mutex;
struct se_device *tg_pt_gp_dev;
struct config_group tg_pt_gp_group;
struct list_head tg_pt_gp_list;
struct list_head tg_pt_gp_lun_list;
struct se_lun *tg_pt_gp_alua_lun;
struct se_node_acl *tg_pt_gp_alua_nacl;
struct work_struct tg_pt_gp_transition_work;
struct completion *tg_pt_gp_transition_complete;
};
struct t10_vpd {