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SubjectRe: [PATCH] iscsi: Fix a sleep-in-atomic bug
On 06/01/2017 02:21 PM, Nicholas A. Bellinger wrote:
> Hi Jia-Ju,
>
> On Wed, 2017-05-31 at 11:26 +0800, Jia-Ju Bai wrote:
>> The driver may sleep under a spin lock, and the function call path is:
>> iscsit_tpg_enable_portal_group (acquire the lock by spin_lock)
>> iscsi_update_param_value
>> kstrdup(GFP_KERNEL) --> may sleep
>>
>> To fix it, the "GFP_KERNEL" is replaced with "GFP_ATOMIC".
>>
>> Signed-off-by: Jia-Ju Bai<baijiaju1990@163.com>
>> ---
>> drivers/target/iscsi/iscsi_target_parameters.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
> Btw, the use of tpg->tpg_state_lock in iscsit_tpg_enable_portal_group()
> while checking existing state and calling iscsi_update_param_value() is
> not necessary, since lio_target_tpg_enable_store() is already holding
> iscsit_get_tpg() -> tpg->tpg_access_lock.
>
> How about the following instead to only take tpg->tpg_state_lock when
> updating tpg->tpg_state instead..?
>
> diff --git a/drivers/target/iscsi/iscsi_target_tpg.c b/drivers/target/iscsi/iscsi_target_tpg.c
> index 2e7e08d..abaabba 100644
> --- a/drivers/target/iscsi/iscsi_target_tpg.c
> +++ b/drivers/target/iscsi/iscsi_target_tpg.c
> @@ -311,11 +311,9 @@ int iscsit_tpg_enable_portal_group(struct iscsi_portal_group *tpg)
> struct iscsi_tiqn *tiqn = tpg->tpg_tiqn;
> int ret;
>
> - spin_lock(&tpg->tpg_state_lock);
> if (tpg->tpg_state == TPG_STATE_ACTIVE) {
> pr_err("iSCSI target portal group: %hu is already"
> " active, ignoring request.\n", tpg->tpgt);
> - spin_unlock(&tpg->tpg_state_lock);
> return -EINVAL;
> }
> /*
> @@ -324,10 +322,8 @@ int iscsit_tpg_enable_portal_group(struct iscsi_portal_group *tpg)
> * is enforced (as per default), and remove the NONE option.
> */
> param = iscsi_find_param_from_key(AUTHMETHOD, tpg->param_list);
> - if (!param) {
> - spin_unlock(&tpg->tpg_state_lock);
> + if (!param)
> return -EINVAL;
> - }
>
> if (tpg->tpg_attrib.authentication) {
> if (!strcmp(param->value, NONE)) {
> @@ -341,6 +337,7 @@ int iscsit_tpg_enable_portal_group(struct iscsi_portal_group *tpg)
> goto err;
> }
>
> + spin_lock(&tpg->tpg_state_lock);
> tpg->tpg_state = TPG_STATE_ACTIVE;
> spin_unlock(&tpg->tpg_state_lock);
>
> @@ -353,7 +350,6 @@ int iscsit_tpg_enable_portal_group(struct iscsi_portal_group *tpg)
> return 0;
>
> err:
> - spin_unlock(&tpg->tpg_state_lock);
> return ret;
> }
>
I think it is fine to me.

Thanks,
Jia-Ju Bai

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