To ensure that a module does not unload in the middle of a checkpoint or a restart operation, pin (module_get) all the modules during either operation. For that, add a new memeber ->owner in ckpt_obj_ops.
Also add a counter that keeps track of how many module_gets we have going on, to properly handle new modules that register when an operation is underway. This is a proof of concept, applies on top of the patch that introduces objhash on rc7 (patch 33). Todo: - I put the initialization part in init_*_ctx(), but it could be moved to ckpt_ctx_alloc() which is common to both checkpoint and restart. - If this is ok, then additional patches should adjust those modules that indeed register... Signed-off-by: Oren Laadan <[email protected]> --- diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h index 2f5af3c..4ed8a8c 100644 --- a/include/linux/checkpoint.h +++ b/include/linux/checkpoint.h @@ -40,11 +40,13 @@ extern long do_sys_restart(pid_t pid, int fd, #define CKPT_CTX_RESTART_BIT 1 #define CKPT_CTX_SUCCESS_BIT 2 #define CKPT_CTX_ERROR_BIT 3 +#define CKPT_CTX_PINNED_BIT 4 #define CKPT_CTX_CHECKPOINT (1 << CKPT_CTX_CHECKPOINT_BIT) #define CKPT_CTX_RESTART (1 << CKPT_CTX_RESTART_BIT) #define CKPT_CTX_SUCCESS (1 << CKPT_CTX_SUCCESS_BIT) #define CKPT_CTX_ERROR (1 << CKPT_CTX_ERROR_BIT) +#define CKPT_CTX_PINNED (1 << CKPT_CTX_PINNED_BIT) /* ckpt_ctx: uflags */ #define CHECKPOINT_USER_FLAGS CHECKPOINT_SUBTREE @@ -107,6 +109,9 @@ static inline int ckpt_get_error(struct ckpt_ctx *ctx) extern void restore_notify_error(struct ckpt_ctx *ctx); /* obj_hash */ +extern int ckpt_obj_module_get(void); +extern void ckpt_obj_module_put(void); + extern void ckpt_obj_hash_free(struct ckpt_ctx *ctx); extern int ckpt_obj_hash_alloc(struct ckpt_ctx *ctx); @@ -284,6 +289,7 @@ extern void _ckpt_msg_complete(struct ckpt_ctx *ctx); struct ckpt_obj_ops; extern int register_checkpoint_obj(const struct ckpt_obj_ops *ops); +extern void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops); #else /* CONFIG_CHEKCPOINT */ @@ -293,6 +299,10 @@ static inline int register_checkpoint_obj(const struct ckpt_obj_ops *ops) return 0; } +static inline void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops) +{ +} + #endif /* CONFIG_CHECKPOINT */ #endif /* __KERNEL__ */ diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h index 912e06a..8035556 100644 --- a/include/linux/checkpoint_types.h +++ b/include/linux/checkpoint_types.h @@ -79,6 +79,7 @@ struct ckpt_obj_ops { int (*ref_grab)(void *ptr); int (*checkpoint)(struct ckpt_ctx *ctx, void *ptr); void *(*restore)(struct ckpt_ctx *ctx); + struct module *owner; }; diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c index f451f8f..1a08bfb 100644 --- a/kernel/checkpoint/checkpoint.c +++ b/kernel/checkpoint/checkpoint.c @@ -473,6 +473,7 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid) { struct task_struct *task; struct nsproxy *nsproxy; + int ret; /* * No need for explicit cleanup here, because if an error @@ -514,6 +515,12 @@ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid) return -EINVAL; /* cleanup by ckpt_ctx_free() */ } + /* pin down modules - cleanup by ckpt_ctx_free() */ + ret = ckpt_obj_module_get(); + if (ret < 0) + return ret; + ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED); + return 0; } diff --git a/kernel/checkpoint/objhash.c b/kernel/checkpoint/objhash.c index 1ee06d0..db795e3 100644 --- a/kernel/checkpoint/objhash.c +++ b/kernel/checkpoint/objhash.c @@ -45,17 +45,80 @@ static const struct ckpt_obj_ops *ckpt_obj_ops[CKPT_OBJ_MAX] = { [CKPT_OBJ_IGNORE] = &ckpt_obj_ignored_ops, }; +static int ckpt_obj_pinned_count; +static DEFINE_SPINLOCK(ckpt_obj_pinned_lock); + int register_checkpoint_obj(const struct ckpt_obj_ops *ops) { + int ret = -EINVAL; + int i; + if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX) return -EINVAL; - if (ckpt_obj_ops[ops->obj_type] != NULL) - return -EINVAL; - ckpt_obj_ops[ops->obj_type] = ops; - return 0; + spin_lock(&ckpt_obj_pinned_lock); + if (ckpt_obj_ops[ops->obj_type] == NULL) { + if (ops->owner) { + for (i = 0; i < ckpt_obj_pinned_count) + __module_get(owner->module); + } + ckpt_obj_ops[ops->obj_type] = ops; + ret = 0; + } + spin_unlock(&ckpt_obj_pinned_lock); + return ret; } EXPORT_SYMBOL(register_checkpoint_obj); +void unregister_checkpoint_obj(const struct ckpt_obj_ops *ops) +{ + if (ops->obj_type < 0 || ops->obj_type >= CKPT_OBJ_MAX) + return; + spin_lock(&ckpt_obj_pinned_lock); + if (ckpt_obj_ops[ops->obj_type] == ops) + ckpt_obj_ops[ops->obj_type] = NULL; + spin_unlock(&ckpt_obj_pinned_lock); + return ret; +} +EXPORT_SYMBOL(unregister_checkpoint_obj); + +static void _ckpt_obj_module_put(int last) +{ + int i; + + for (i = 0; i < last; i++) { + if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner) + continue; + module_put(ckpt_obj_ops[i]->owner); + } +} +void ckpt_obj_module_put(void) +{ + spin_lock(&ckpt_obj_pinned_lock); + _ckpt_obj_module_put(CKPT_OBJ_MAX); + ckpt_obj_pinned_count--; + spin_unlock(&ckpt_obj_pinned_lock); +} + +int ckpt_obj_module_get(void) +{ + int i, ret = 0; + + spin_lock(&ckpt_obj_pinned_lock); + for (i = 0; i < CKPT_OBJ_MAX; i++) { + if (!ckpt_obj_ops[i] || !ckpt_obj_ops[i]->owner) + continue; + ret = try_module_get(ckpt_obj_ops[i]->owner); + if (ret < 0) + break; + } + if (ret < 0) + _ckpt_obj_module_put(i); + else + ckpt_obj_pinned_count++; + spin_unlock(&ckpt_obj_pinned_lock); + return ret; +} + #define CKPT_OBJ_HASH_NBITS 10 #define CKPT_OBJ_HASH_TOTAL (1UL << CKPT_OBJ_HASH_NBITS) diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c index 437de4f..582e1f1 100644 --- a/kernel/checkpoint/restart.c +++ b/kernel/checkpoint/restart.c @@ -1084,6 +1084,12 @@ static int init_restart_ctx(struct ckpt_ctx *ctx, pid_t pid) ctx->active_pid = -1; /* see restore_activate_next, get_active_pid */ + /* pin down modules - cleanup by ckpt_ctx_free() */ + ret = ckpt_obj_module_get(); + if (ret < 0) + return ret; + ckpt_ctx_set_kflag(ctx, CKPT_CTX_PINNED); + return 0; } diff --git a/kernel/checkpoint/sys.c b/kernel/checkpoint/sys.c index 5e84915..e1a1f96 100644 --- a/kernel/checkpoint/sys.c +++ b/kernel/checkpoint/sys.c @@ -217,6 +217,10 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx) kfree(ctx->pids_arr); + /* un-pin modules */ + if (ctx->kflags & CKPT_CTX_PINNED) + ckpt_obj_module_put(); + kfree(ctx); } _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
