diff options
Diffstat (limited to 'block/blktrace.c')
| -rw-r--r-- | block/blktrace.c | 538 |
1 files changed, 538 insertions, 0 deletions
diff --git a/block/blktrace.c b/block/blktrace.c new file mode 100644 index 0000000..36f3a17 --- /dev/null +++ b/block/blktrace.c @@ -0,0 +1,538 @@ +/* + * Copyright (C) 2006 Jens Axboe <axboe@suse.de> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + */ +#include <linux/config.h> +#include <linux/kernel.h> +#include <linux/blkdev.h> +#include <linux/blktrace_api.h> +#include <linux/percpu.h> +#include <linux/init.h> +#include <linux/mutex.h> +#include <linux/debugfs.h> +#include <asm/uaccess.h> + +static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, }; +static unsigned int blktrace_seq __read_mostly = 1; + +/* + * Send out a notify for this process, if we haven't done so since a trace + * started + */ +static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk) +{ + struct blk_io_trace *t; + + t = relay_reserve(bt->rchan, sizeof(*t) + sizeof(tsk->comm)); + if (t) { + t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; + t->device = bt->dev; + t->action = BLK_TC_ACT(BLK_TC_NOTIFY); + t->pid = tsk->pid; + t->cpu = smp_processor_id(); + t->pdu_len = sizeof(tsk->comm); + memcpy((void *) t + sizeof(*t), tsk->comm, t->pdu_len); + tsk->btrace_seq = blktrace_seq; + } +} + +static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector, + pid_t pid) +{ + if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0) + return 1; + if (sector < bt->start_lba || sector > bt->end_lba) + return 1; + if (bt->pid && pid != bt->pid) + return 1; + + return 0; +} + +/* + * Data direction bit lookup + */ +static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) }; + +/* + * Bio action bits of interest + */ +static u32 bio_act[3] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC) }; + +/* + * More could be added as needed, taking care to increment the decrementer + * to get correct indexing + */ +#define trace_barrier_bit(rw) \ + (((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0)) +#define trace_sync_bit(rw) \ + (((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1)) + +/* + * The worker for the various blk_add_trace*() types. Fills out a + * blk_io_trace structure and places it in a per-cpu subbuffer. + */ +void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes, + int rw, u32 what, int error, int pdu_len, void *pdu_data) +{ + struct task_struct *tsk = current; + struct blk_io_trace *t; + unsigned long flags; + unsigned long *sequence; + pid_t pid; + int cpu; + + if (unlikely(bt->trace_state != Blktrace_running)) + return; + + what |= ddir_act[rw & WRITE]; + what |= bio_act[trace_barrier_bit(rw)]; + what |= bio_act[trace_sync_bit(rw)]; + + pid = tsk->pid; + if (unlikely(act_log_check(bt, what, sector, pid))) + return; + + /* + * A word about the locking here - we disable interrupts to reserve + * some space in the relay per-cpu buffer, to prevent an irq + * from coming in and stepping on our toes. Once reserved, it's + * enough to get preemption disabled to prevent read of this data + * before we are through filling it. get_cpu()/put_cpu() does this + * for us + */ + local_irq_save(flags); + + if (unlikely(tsk->btrace_seq != blktrace_seq)) + trace_note_tsk(bt, tsk); + + t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len); + if (t) { + cpu = smp_processor_id(); + sequence = per_cpu_ptr(bt->sequence, cpu); + + t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; + t->sequence = ++(*sequence); + t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu); + t->sector = sector; + t->bytes = bytes; + t->action = what; + t->pid = pid; + t->device = bt->dev; + t->cpu = cpu; + t->error = error; + t->pdu_len = pdu_len; + + if (pdu_len) + memcpy((void *) t + sizeof(*t), pdu_data, pdu_len); + } + + local_irq_restore(flags); +} + +EXPORT_SYMBOL_GPL(__blk_add_trace); + +static struct dentry *blk_tree_root; +static struct mutex blk_tree_mutex; +static unsigned int root_users; + +static inline void blk_remove_root(void) +{ + if (blk_tree_root) { + debugfs_remove(blk_tree_root); + blk_tree_root = NULL; + } +} + +static void blk_remove_tree(struct dentry *dir) +{ + mutex_lock(&blk_tree_mutex); + debugfs_remove(dir); + if (--root_users == 0) + blk_remove_root(); + mutex_unlock(&blk_tree_mutex); +} + +static struct dentry *blk_create_tree(const char *blk_name) +{ + struct dentry *dir = NULL; + + mutex_lock(&blk_tree_mutex); + + if (!blk_tree_root) { + blk_tree_root = debugfs_create_dir("block", NULL); + if (!blk_tree_root) + goto err; + } + + dir = debugfs_create_dir(blk_name, blk_tree_root); + if (dir) + root_users++; + else + blk_remove_root(); + +err: + mutex_unlock(&blk_tree_mutex); + return dir; +} + +static void blk_trace_cleanup(struct blk_trace *bt) +{ + relay_close(bt->rchan); + debugfs_remove(bt->dropped_file); + blk_remove_tree(bt->dir); + free_percpu(bt->sequence); + kfree(bt); +} + +static int blk_trace_remove(request_queue_t *q) +{ + struct blk_trace *bt; + + bt = xchg(&q->blk_trace, NULL); + if (!bt) + return -EINVAL; + + if (bt->trace_state == Blktrace_setup || + bt->trace_state == Blktrace_stopped) + blk_trace_cleanup(bt); + + return 0; +} + +static int blk_dropped_open(struct inode *inode, struct file *filp) +{ + filp->private_data = inode->u.generic_ip; + + return 0; +} + +static ssize_t blk_dropped_read(struct file *filp, char __user *buffer, + size_t count, loff_t *ppos) +{ + struct blk_trace *bt = filp->private_data; + char buf[16]; + + snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped)); + + return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf)); +} + +static struct file_operations blk_dropped_fops = { + .owner = THIS_MODULE, + .open = blk_dropped_open, + .read = blk_dropped_read, +}; + +/* + * Keep track of how many times we encountered a full subbuffer, to aid + * the user space app in telling how many lost events there were. + */ +static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf, + void *prev_subbuf, size_t prev_padding) +{ + struct blk_trace *bt; + + if (!relay_buf_full(buf)) + return 1; + + bt = buf->chan->private_data; + atomic_inc(&bt->dropped); + return 0; +} + +static int blk_remove_buf_file_callback(struct dentry *dentry) +{ + debugfs_remove(dentry); + return 0; +} + +static struct dentry *blk_create_buf_file_callback(const char *filename, + struct dentry *parent, + int mode, + struct rchan_buf *buf, + int *is_global) +{ + return debugfs_create_file(filename, mode, parent, buf, + &relay_file_operations); +} + +static struct rchan_callbacks blk_relay_callbacks = { + .subbuf_start = blk_subbuf_start_callback, + .create_buf_file = blk_create_buf_file_callback, + .remove_buf_file = blk_remove_buf_file_callback, +}; + +/* + * Setup everything required to start tracing + */ +static int blk_trace_setup(request_queue_t *q, struct block_device *bdev, + char __user *arg) +{ + struct blk_user_trace_setup buts; + struct blk_trace *old_bt, *bt = NULL; + struct dentry *dir = NULL; + char b[BDEVNAME_SIZE]; + int ret, i; + + if (copy_from_user(&buts, arg, sizeof(buts))) + return -EFAULT; + + if (!buts.buf_size || !buts.buf_nr) + return -EINVAL; + + strcpy(buts.name, bdevname(bdev, b)); + + /* + * some device names have larger paths - convert the slashes + * to underscores for this to work as expected + */ + for (i = 0; i < strlen(buts.name); i++) + if (buts.name[i] == '/') + buts.name[i] = '_'; + + if (copy_to_user(arg, &buts, sizeof(buts))) + return -EFAULT; + + ret = -ENOMEM; + bt = kzalloc(sizeof(*bt), GFP_KERNEL); + if (!bt) + goto err; + + bt->sequence = alloc_percpu(unsigned long); + if (!bt->sequence) + goto err; + + ret = -ENOENT; + dir = blk_create_tree(buts.name); + if (!dir) + goto err; + + bt->dir = dir; + bt->dev = bdev->bd_dev; + atomic_set(&bt->dropped, 0); + + ret = -EIO; + bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops); + if (!bt->dropped_file) + goto err; + + bt->rchan = relay_open("trace", dir, buts.buf_size, buts.buf_nr, &blk_relay_callbacks); + if (!bt->rchan) + goto err; + bt->rchan->private_data = bt; + + bt->act_mask = buts.act_mask; + if (!bt->act_mask) + bt->act_mask = (u16) -1; + + bt->start_lba = buts.start_lba; + bt->end_lba = buts.end_lba; + if (!bt->end_lba) + bt->end_lba = -1ULL; + + bt->pid = buts.pid; + bt->trace_state = Blktrace_setup; + + ret = -EBUSY; + old_bt = xchg(&q->blk_trace, bt); + if (old_bt) { + (void) xchg(&q->blk_trace, old_bt); + goto err; + } + + return 0; +err: + if (dir) + blk_remove_tree(dir); + if (bt) { + if (bt->dropped_file) + debugfs_remove(bt->dropped_file); + if (bt->sequence) + free_percpu(bt->sequence); + if (bt->rchan) + relay_close(bt->rchan); + kfree(bt); + } + return ret; +} + +static int blk_trace_startstop(request_queue_t *q, int start) +{ + struct blk_trace *bt; + int ret; + + if ((bt = q->blk_trace) == NULL) + return -EINVAL; + + /* + * For starting a trace, we can transition from a setup or stopped + * trace. For stopping a trace, the state must be running + */ + ret = -EINVAL; + if (start) { + if (bt->trace_state == Blktrace_setup || + bt->trace_state == Blktrace_stopped) { + blktrace_seq++; + smp_mb(); + bt->trace_state = Blktrace_running; + ret = 0; + } + } else { + if (bt->trace_state == Blktrace_running) { + bt->trace_state = Blktrace_stopped; + relay_flush(bt->rchan); + ret = 0; + } + } + + return ret; +} + +/** + * blk_trace_ioctl: - handle the ioctls associated with tracing + * @bdev: the block device + * @cmd: the ioctl cmd + * @arg: the argument data, if any + * + **/ +int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg) +{ + request_queue_t *q; + int ret, start = 0; + + q = bdev_get_queue(bdev); + if (!q) + return -ENXIO; + + mutex_lock(&bdev->bd_mutex); + + switch (cmd) { + case BLKTRACESETUP: + ret = blk_trace_setup(q, bdev, arg); + break; + case BLKTRACESTART: + start = 1; + case BLKTRACESTOP: + ret = blk_trace_startstop(q, start); + break; + case BLKTRACETEARDOWN: + ret = blk_trace_remove(q); + break; + default: + ret = -ENOTTY; + break; + } + + mutex_unlock(&bdev->bd_mutex); + return ret; +} + +/** + * blk_trace_shutdown: - stop and cleanup trace structures + * @q: the request queue associated with the device + * + **/ +void blk_trace_shutdown(request_queue_t *q) +{ + blk_trace_startstop(q, 0); + blk_trace_remove(q); +} + +/* + * Average offset over two calls to sched_clock() with a gettimeofday() + * in the middle + */ +static void blk_check_time(unsigned long long *t) +{ + unsigned long long a, b; + struct timeval tv; + + a = sched_clock(); + do_gettimeofday(&tv); + b = sched_clock(); + + *t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000; + *t -= (a + b) / 2; +} + +static void blk_trace_check_cpu_time(void *data) +{ + unsigned long long *t; + int cpu = get_cpu(); + + t = &per_cpu(blk_trace_cpu_offset, cpu); + + /* + * Just call it twice, hopefully the second call will be cache hot + * and a little more precise + */ + blk_check_time(t); + blk_check_time(t); + + put_cpu(); +} + +/* + * Call blk_trace_check_cpu_time() on each CPU to calibrate our inter-CPU + * timings + */ +static void blk_trace_calibrate_offsets(void) +{ + unsigned long flags; + + smp_call_function(blk_trace_check_cpu_time, NULL, 1, 1); + local_irq_save(flags); + blk_trace_check_cpu_time(NULL); + local_irq_restore(flags); +} + +static void blk_trace_set_ht_offsets(void) +{ +#if defined(CONFIG_SCHED_SMT) + int cpu, i; + + /* + * now make sure HT siblings have the same time offset + */ + preempt_disable(); + for_each_online_cpu(cpu) { + unsigned long long *cpu_off, *sibling_off; + + for_each_cpu_mask(i, cpu_sibling_map[cpu]) { + if (i == cpu) + continue; + + cpu_off = &per_cpu(blk_trace_cpu_offset, cpu); + sibling_off = &per_cpu(blk_trace_cpu_offset, i); + *sibling_off = *cpu_off; + } + } + preempt_enable(); +#endif +} + +static __init int blk_trace_init(void) +{ + mutex_init(&blk_tree_mutex); + blk_trace_calibrate_offsets(); + blk_trace_set_ht_offsets(); + + return 0; +} + +module_init(blk_trace_init); + |