/* FS-Cache worker operation management routines * * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * See Documentation/filesystems/caching/operations.txt */ #define FSCACHE_DEBUG_LEVEL OPERATION #include <linux/module.h> #include "internal.h" atomic_t fscache_op_debug_id; EXPORT_SYMBOL(fscache_op_debug_id); /** * fscache_enqueue_operation - Enqueue an operation for processing * @op: The operation to enqueue * * Enqueue an operation for processing by the FS-Cache thread pool. * * This will get its own ref on the object. */ void fscache_enqueue_operation(struct fscache_operation *op) { _enter("{OBJ%x OP%x,%u}", op->object->debug_id, op->debug_id, atomic_read(&op->usage)); ASSERT(op->processor != NULL); ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE); ASSERTCMP(atomic_read(&op->usage), >, 0); if (list_empty(&op->pend_link)) { switch (op->flags & FSCACHE_OP_TYPE) { case FSCACHE_OP_FAST: _debug("queue fast"); atomic_inc(&op->usage); if (!schedule_work(&op->fast_work)) fscache_put_operation(op); break; case FSCACHE_OP_SLOW: _debug("queue slow"); slow_work_enqueue(&op->slow_work); break; case FSCACHE_OP_MYTHREAD: _debug("queue for caller's attention"); break; default: printk(KERN_ERR "FS-Cache: Unexpected op type %lx", op->flags); BUG(); break; } fscache_stat(&fscache_n_op_enqueue); } } EXPORT_SYMBOL(fscache_enqueue_operation); /* * start an op running */ static void fscache_run_op(struct fscache_object *object, struct fscache_operation *op) { object->n_in_progress++; if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags)) wake_up_bit(&op->flags, FSCACHE_OP_WAITING); if (op->processor) fscache_enqueue_operation(op); fscache_stat(&fscache_n_op_run); } /* * submit an exclusive operation for an object * - other ops are excluded from running simultaneously with this one * - this gets any extra refs it needs on an op */ int fscache_submit_exclusive_op(struct fscache_object *object, struct fscache_operation *op) { int ret; _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id); spin_lock(&object->lock); ASSERTCMP(object->n_ops, >=, object->n_in_progress); ASSERTCMP(object->n_ops, >=, object->n_exclusive); ret = -ENOBUFS; if (fscache_object_is_active(object)) { op->object = object; object->n_ops++; object->n_exclusive++; /* reads and writes must wait */ if (object->n_ops > 0) { atomic_inc(&op->usage); list_add_tail(&op->pend_link, &object->pending_ops); fscache_stat(&fscache_n_op_pend); } else if (!list_empty(&object->pending_ops)) { atomic_inc(&op->usage); list_add_tail(&op->pend_link, &object->pending_ops); fscache_stat(&fscache_n_op_pend); fscache_start_operations(object); } else { ASSERTCMP(object->n_in_progress, ==, 0); fscache_run_op(object, op); } /* need to issue a new write op after this */ clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags); ret = 0; } else if (object->state == FSCACHE_OBJECT_CREATING) { op->object = object; object->n_ops++; object->n_exclusive++; /* reads and writes must wait */ atomic_inc(&op->usage); list_add_tail(&op->pend_link, &object->pending_ops); fscache_stat(&fscache_n_op_pend); ret = 0; } else { /* not allowed to submit ops in any other state */ BUG(); } spin_unlock(&object->lock); return ret; } /* * report an unexpected submission */ static void fscache_report_unexpected_submission(struct fscache_object *object, struct fscache_operation *op, unsigned long ostate) { static bool once_only; struct fscache_operation *p; unsigned n; if (once_only) return; once_only = true; kdebug("unexpected submission OP%x [OBJ%x %s]", op->debug_id, object->debug_id, fscache_object_states[object->state]); kdebug("objstate=%s [%s]", fscache_object_states[object->state], fscache_object_states[ostate]); kdebug("objflags=%lx", object->flags); kdebug("objevent=%lx [%lx]", object->events, object->event_mask); kdebug("ops=%u inp=%u exc=%u", object->n_ops, object->n_in_progress, object->n_exclusive); if (!list_empty(&object->pending_ops)) { n = 0; list_for_each_entry(p, &object->pending_ops, pend_link) { ASSERTCMP(p->object, ==, object); kdebug("%p %p", op->processor, op->release); n++; } kdebug("n=%u", n); } dump_stack(); } /* * submit an operation for an object * - objects may be submitted only in the following states: * - during object creation (write ops may be submitted) * - whilst the object is active * - after an I/O error incurred in one of the two above states (op rejected) * - this gets any extra refs it needs on an op */ int fscache_submit_op(struct fscache_object *object, struct fscache_operation *op) { unsigned long ostate; int ret; _enter("{OBJ%x OP%x},{%u}", object->debug_id, op->debug_id, atomic_read(&op->usage)); ASSERTCMP(atomic_read(&op->usage), >, 0); spin_lock(&object->lock); ASSERTCMP(object->n_ops, >=, object->n_in_progress); ASSERTCMP(object->n_ops, >=, object->n_exclusive); ostate = object->state; smp_rmb(); if (fscache_object_is_active(object)) { op->object = object; object->n_ops++; if (object->n_exclusive > 0) { atomic_inc(&op->usage); list_add_tail(&op->pend_link, &object->pending_ops); fscache_stat(&fscache_n_op_pend); } else if (!list_empty(&object->pending_ops)) { atomic_inc(&op->usage); list_add_tail(&op->pend_link, &object->pending_ops); fscache_stat(&fscache_n_op_pend); fscache_start_operations(object); } else { ASSERTCMP(object->n_exclusive, ==, 0); fscache_run_op(object, op); } ret = 0; } else if (object->state == FSCACHE_OBJECT_CREATING) { op->object = object; object->n_ops++; atomic_inc(&op->usage); list_add_tail(&op->pend_link, &object->pending_ops); fscache_stat(&fscache_n_op_pend); ret = 0; } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) { fscache_report_unexpected_submission(object, op, ostate); ASSERT(!fscache_object_is_active(object)); ret = -ENOBUFS; } else { ret = -ENOBUFS; } spin_unlock(&object->lock); return ret; } /* * queue an object for withdrawal on error, aborting all following asynchronous * operations */ void fscache_abort_object(struct fscache_object *object) { _enter("{OBJ%x}", object->debug_id); fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR); } /* * jump start the operation processing on an object * - caller must hold object->lock */ void fscache_start_operations(struct fscache_object *object) { struct fscache_operation *op; bool stop = false; while (!list_empty(&object->pending_ops) && !stop) { op = list_entry(object->pending_ops.next, struct fscache_operation, pend_link); if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) { if (object->n_in_progress > 0) break; stop = true; } list_del_init(&op->pend_link); object->n_in_progress++; if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags)) wake_up_bit(&op->flags, FSCACHE_OP_WAITING); if (op->processor) fscache_enqueue_operation(op); /* the pending queue was holding a ref on the object */ fscache_put_operation(op); } ASSERTCMP(object->n_in_progress, <=, object->n_ops); _debug("woke %d ops on OBJ%x", object->n_in_progress, object->debug_id); } /* * release an operation * - queues pending ops if this is the last in-progress op */ void fscache_put_operation(struct fscache_operation *op) { struct fscache_object *object; struct fscache_cache *cache; _enter("{OBJ%x OP%x,%d}", op->object->debug_id, op->debug_id, atomic_read(&op->usage)); ASSERTCMP(atomic_read(&op->usage), >, 0); if (!atomic_dec_and_test(&op->usage)) return; _debug("PUT OP"); if (test_and_set_bit(FSCACHE_OP_DEAD, &op->flags)) BUG(); fscache_stat(&fscache_n_op_release); if (op->release) { op->release(op); op->release = NULL; } object = op->object; /* now... we may get called with the object spinlock held, so we * complete the cleanup here only if we can immediately acquire the * lock, and defer it otherwise */ if (!spin_trylock(&object->lock)) { _debug("defer put"); fscache_stat(&fscache_n_op_deferred_release); cache = object->cache; spin_lock(&cache->op_gc_list_lock); list_add_tail(&op->pend_link, &cache->op_gc_list); spin_unlock(&cache->op_gc_list_lock); schedule_work(&cache->op_gc); _leave(" [defer]"); return; } if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) { ASSERTCMP(object->n_exclusive, >, 0); object->n_exclusive--; } ASSERTCMP(object->n_in_progress, >, 0); object->n_in_progress--; if (object->n_in_progress == 0) fscache_start_operations(object); ASSERTCMP(object->n_ops, >, 0); object->n_ops--; if (object->n_ops == 0) fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED); spin_unlock(&object->lock); kfree(op); _leave(" [done]"); } EXPORT_SYMBOL(fscache_put_operation); /* * garbage collect operations that have had their release deferred */ void fscache_operation_gc(struct work_struct *work) { struct fscache_operation *op; struct fscache_object *object; struct fscache_cache *cache = container_of(work, struct fscache_cache, op_gc); int count = 0; _enter(""); do { spin_lock(&cache->op_gc_list_lock); if (list_empty(&cache->op_gc_list)) { spin_unlock(&cache->op_gc_list_lock); break; } op = list_entry(cache->op_gc_list.next, struct fscache_operation, pend_link); list_del(&op->pend_link); spin_unlock(&cache->op_gc_list_lock); object = op->object; _debug("GC DEFERRED REL OBJ%x OP%x", object->debug_id, op->debug_id); fscache_stat(&fscache_n_op_gc); ASSERTCMP(atomic_read(&op->usage), ==, 0); spin_lock(&object->lock); if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) { ASSERTCMP(object->n_exclusive, >, 0); object->n_exclusive--; } ASSERTCMP(object->n_in_progress, >, 0); object->n_in_progress--; if (object->n_in_progress == 0) fscache_start_operations(object); ASSERTCMP(object->n_ops, >, 0); object->n_ops--; if (object->n_ops == 0) fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED); spin_unlock(&object->lock); } while (count++ < 20); if (!list_empty(&cache->op_gc_list)) schedule_work(&cache->op_gc); _leave(""); } /* * allow the slow work item processor to get a ref on an operation */ static int fscache_op_get_ref(struct slow_work *work) { struct fscache_operation *op = container_of(work, struct fscache_operation, slow_work); atomic_inc(&op->usage); return 0; } /* * allow the slow work item processor to discard a ref on an operation */ static void fscache_op_put_ref(struct slow_work *work) { struct fscache_operation *op = container_of(work, struct fscache_operation, slow_work); fscache_put_operation(op); } /* * execute an operation using the slow thread pool to provide processing context * - the caller holds a ref to this object, so we don't need to hold one */ static void fscache_op_execute(struct slow_work *work) { struct fscache_operation *op = container_of(work, struct fscache_operation, slow_work); unsigned long start; _enter("{OBJ%x OP%x,%d}", op->object->debug_id, op->debug_id, atomic_read(&op->usage)); ASSERT(op->processor != NULL); start = jiffies; op->processor(op); fscache_hist(fscache_ops_histogram, start); _leave(""); } const struct slow_work_ops fscache_op_slow_work_ops = { .get_ref = fscache_op_get_ref, .put_ref = fscache_op_put_ref, .execute = fscache_op_execute, };