[PATCH] uml: revert block driver use of host AIO
The patch to use host AIO support that I submitted early after 2.6.13 exposed
some problems in the block driver. I have fixes for these, but am not
comfortable putting them into 2.6.14 at this late date. So, this patch reverts
the use of host AIO.
I will resubmit the original patch, plus fixes to the driver after 2.6.14
in order to get a reasonable amount of testing before they're exposed to
the general public.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index e77a38d..f731343 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -35,7 +35,6 @@
#include "linux/blkpg.h"
#include "linux/genhd.h"
#include "linux/spinlock.h"
-#include "asm/atomic.h"
#include "asm/segment.h"
#include "asm/uaccess.h"
#include "asm/irq.h"
@@ -54,21 +53,20 @@
#include "mem.h"
#include "mem_kern.h"
#include "cow.h"
-#include "aio.h"
enum ubd_req { UBD_READ, UBD_WRITE };
struct io_thread_req {
- enum aio_type op;
+ enum ubd_req op;
int fds[2];
unsigned long offsets[2];
unsigned long long offset;
unsigned long length;
char *buffer;
int sectorsize;
- int bitmap_offset;
- long bitmap_start;
- long bitmap_end;
+ unsigned long sector_mask;
+ unsigned long long cow_offset;
+ unsigned long bitmap_words[2];
int error;
};
@@ -82,31 +80,28 @@
unsigned long *bitmap_len_out,
int *data_offset_out);
extern int read_cow_bitmap(int fd, void *buf, int offset, int len);
-extern void do_io(struct io_thread_req *req, struct request *r,
- unsigned long *bitmap);
+extern void do_io(struct io_thread_req *req);
-static inline int ubd_test_bit(__u64 bit, void *data)
+static inline int ubd_test_bit(__u64 bit, unsigned char *data)
{
- unsigned char *buffer = data;
__u64 n;
int bits, off;
- bits = sizeof(buffer[0]) * 8;
+ bits = sizeof(data[0]) * 8;
n = bit / bits;
off = bit % bits;
- return((buffer[n] & (1 << off)) != 0);
+ return((data[n] & (1 << off)) != 0);
}
-static inline void ubd_set_bit(__u64 bit, void *data)
+static inline void ubd_set_bit(__u64 bit, unsigned char *data)
{
- unsigned char *buffer = data;
__u64 n;
int bits, off;
- bits = sizeof(buffer[0]) * 8;
+ bits = sizeof(data[0]) * 8;
n = bit / bits;
off = bit % bits;
- buffer[n] |= (1 << off);
+ data[n] |= (1 << off);
}
/*End stuff from ubd_user.h*/
@@ -115,6 +110,8 @@
static DEFINE_SPINLOCK(ubd_io_lock);
static DEFINE_SPINLOCK(ubd_lock);
+static void (*do_ubd)(void);
+
static int ubd_open(struct inode * inode, struct file * filp);
static int ubd_release(struct inode * inode, struct file * file);
static int ubd_ioctl(struct inode * inode, struct file * file,
@@ -161,8 +158,6 @@
int data_offset;
};
-#define MAX_SG 64
-
struct ubd {
char *file;
int count;
@@ -173,7 +168,6 @@
int no_cow;
struct cow cow;
struct platform_device pdev;
- struct scatterlist sg[MAX_SG];
};
#define DEFAULT_COW { \
@@ -466,114 +460,81 @@
);
static void do_ubd_request(request_queue_t * q);
-static int in_ubd;
+
+/* Only changed by ubd_init, which is an initcall. */
+int thread_fd = -1;
/* Changed by ubd_handler, which is serialized because interrupts only
* happen on CPU 0.
*/
int intr_count = 0;
-static void ubd_end_request(struct request *req, int bytes, int uptodate)
-{
- if (!end_that_request_first(req, uptodate, bytes >> 9)) {
- add_disk_randomness(req->rq_disk);
- end_that_request_last(req);
- }
-}
-
/* call ubd_finish if you need to serialize */
-static void __ubd_finish(struct request *req, int bytes)
+static void __ubd_finish(struct request *req, int error)
{
- if(bytes < 0){
- ubd_end_request(req, 0, 0);
- return;
- }
+ int nsect;
- ubd_end_request(req, bytes, 1);
+ if(error){
+ end_request(req, 0);
+ return;
+ }
+ nsect = req->current_nr_sectors;
+ req->sector += nsect;
+ req->buffer += nsect << 9;
+ req->errors = 0;
+ req->nr_sectors -= nsect;
+ req->current_nr_sectors = 0;
+ end_request(req, 1);
}
-static inline void ubd_finish(struct request *req, int bytes)
+static inline void ubd_finish(struct request *req, int error)
{
- spin_lock(&ubd_io_lock);
- __ubd_finish(req, bytes);
- spin_unlock(&ubd_io_lock);
+ spin_lock(&ubd_io_lock);
+ __ubd_finish(req, error);
+ spin_unlock(&ubd_io_lock);
}
-struct bitmap_io {
- atomic_t count;
- struct aio_context aio;
-};
+/* Called without ubd_io_lock held */
+static void ubd_handler(void)
+{
+ struct io_thread_req req;
+ struct request *rq = elv_next_request(ubd_queue);
+ int n;
-struct ubd_aio {
- struct aio_context aio;
- struct request *req;
- int len;
- struct bitmap_io *bitmap;
- void *bitmap_buf;
-};
-
-static int ubd_reply_fd = -1;
+ do_ubd = NULL;
+ intr_count++;
+ n = os_read_file(thread_fd, &req, sizeof(req));
+ if(n != sizeof(req)){
+ printk(KERN_ERR "Pid %d - spurious interrupt in ubd_handler, "
+ "err = %d\n", os_getpid(), -n);
+ spin_lock(&ubd_io_lock);
+ end_request(rq, 0);
+ spin_unlock(&ubd_io_lock);
+ return;
+ }
+
+ ubd_finish(rq, req.error);
+ reactivate_fd(thread_fd, UBD_IRQ);
+ do_ubd_request(ubd_queue);
+}
static irqreturn_t ubd_intr(int irq, void *dev, struct pt_regs *unused)
{
- struct aio_thread_reply reply;
- struct ubd_aio *aio;
- struct request *req;
- int err, n, fd = (int) (long) dev;
-
- while(1){
- err = os_read_file(fd, &reply, sizeof(reply));
- if(err == -EAGAIN)
- break;
- if(err < 0){
- printk("ubd_aio_handler - read returned err %d\n",
- -err);
- break;
- }
-
- aio = container_of(reply.data, struct ubd_aio, aio);
- n = reply.err;
-
- if(n == 0){
- req = aio->req;
- req->nr_sectors -= aio->len >> 9;
-
- if((aio->bitmap != NULL) &&
- (atomic_dec_and_test(&aio->bitmap->count))){
- aio->aio = aio->bitmap->aio;
- aio->len = 0;
- kfree(aio->bitmap);
- aio->bitmap = NULL;
- submit_aio(&aio->aio);
- }
- else {
- if((req->nr_sectors == 0) &&
- (aio->bitmap == NULL)){
- int len = req->hard_nr_sectors << 9;
- ubd_finish(req, len);
- }
-
- if(aio->bitmap_buf != NULL)
- kfree(aio->bitmap_buf);
- kfree(aio);
- }
- }
- else if(n < 0){
- ubd_finish(aio->req, n);
- if(aio->bitmap != NULL)
- kfree(aio->bitmap);
- if(aio->bitmap_buf != NULL)
- kfree(aio->bitmap_buf);
- kfree(aio);
- }
- }
- reactivate_fd(fd, UBD_IRQ);
-
- do_ubd_request(ubd_queue);
-
+ ubd_handler();
return(IRQ_HANDLED);
}
+/* Only changed by ubd_init, which is an initcall. */
+static int io_pid = -1;
+
+void kill_io_thread(void)
+{
+ if(io_pid != -1)
+ os_kill_process(io_pid, 1);
+}
+
+__uml_exitcall(kill_io_thread);
+
static int ubd_file_size(struct ubd *dev, __u64 *size_out)
{
char *file;
@@ -608,7 +569,7 @@
&dev->cow.data_offset, create_ptr);
if((dev->fd == -ENOENT) && create_cow){
- dev->fd = create_cow_file(dev->file, dev->cow.file,
+ dev->fd = create_cow_file(dev->file, dev->cow.file,
dev->openflags, 1 << 9, PAGE_SIZE,
&dev->cow.bitmap_offset,
&dev->cow.bitmap_len,
@@ -870,10 +831,6 @@
{
int i;
- ubd_reply_fd = init_aio_irq(UBD_IRQ, "ubd", ubd_intr);
- if(ubd_reply_fd < 0)
- printk("Setting up ubd AIO failed, err = %d\n", ubd_reply_fd);
-
devfs_mk_dir("ubd");
if (register_blkdev(MAJOR_NR, "ubd"))
return -1;
@@ -884,7 +841,6 @@
return -1;
}
- blk_queue_max_hw_segments(ubd_queue, MAX_SG);
if (fake_major != MAJOR_NR) {
char name[sizeof("ubd_nnn\0")];
@@ -896,12 +852,40 @@
driver_register(&ubd_driver);
for (i = 0; i < MAX_DEV; i++)
ubd_add(i);
-
return 0;
}
late_initcall(ubd_init);
+int ubd_driver_init(void){
+ unsigned long stack;
+ int err;
+
+ /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
+ if(global_openflags.s){
+ printk(KERN_INFO "ubd: Synchronous mode\n");
+ /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
+ * enough. So use anyway the io thread. */
+ }
+ stack = alloc_stack(0, 0);
+ io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
+ &thread_fd);
+ if(io_pid < 0){
+ printk(KERN_ERR
+ "ubd : Failed to start I/O thread (errno = %d) - "
+ "falling back to synchronous I/O\n", -io_pid);
+ io_pid = -1;
+ return(0);
+ }
+ err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
+ SA_INTERRUPT, "ubd", ubd_dev);
+ if(err != 0)
+ printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
+ return(err);
+}
+
+device_initcall(ubd_driver_init);
+
static int ubd_open(struct inode *inode, struct file *filp)
{
struct gendisk *disk = inode->i_bdev->bd_disk;
@@ -939,55 +923,105 @@
return(0);
}
-static void cowify_bitmap(struct io_thread_req *req, unsigned long *bitmap)
+static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
+ __u64 *cow_offset, unsigned long *bitmap,
+ __u64 bitmap_offset, unsigned long *bitmap_words,
+ __u64 bitmap_len)
{
- __u64 sector = req->offset / req->sectorsize;
- int i;
+ __u64 sector = io_offset >> 9;
+ int i, update_bitmap = 0;
- for(i = 0; i < req->length / req->sectorsize; i++){
- if(ubd_test_bit(sector + i, bitmap))
- continue;
+ for(i = 0; i < length >> 9; i++){
+ if(cow_mask != NULL)
+ ubd_set_bit(i, (unsigned char *) cow_mask);
+ if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
+ continue;
- if(req->bitmap_start == -1)
- req->bitmap_start = sector + i;
- req->bitmap_end = sector + i + 1;
+ update_bitmap = 1;
+ ubd_set_bit(sector + i, (unsigned char *) bitmap);
+ }
- ubd_set_bit(sector + i, bitmap);
- }
+ if(!update_bitmap)
+ return;
+
+ *cow_offset = sector / (sizeof(unsigned long) * 8);
+
+ /* This takes care of the case where we're exactly at the end of the
+ * device, and *cow_offset + 1 is off the end. So, just back it up
+ * by one word. Thanks to Lynn Kerby for the fix and James McMechan
+ * for the original diagnosis.
+ */
+ if(*cow_offset == ((bitmap_len + sizeof(unsigned long) - 1) /
+ sizeof(unsigned long) - 1))
+ (*cow_offset)--;
+
+ bitmap_words[0] = bitmap[*cow_offset];
+ bitmap_words[1] = bitmap[*cow_offset + 1];
+
+ *cow_offset *= sizeof(unsigned long);
+ *cow_offset += bitmap_offset;
+}
+
+static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
+ __u64 bitmap_offset, __u64 bitmap_len)
+{
+ __u64 sector = req->offset >> 9;
+ int i;
+
+ if(req->length > (sizeof(req->sector_mask) * 8) << 9)
+ panic("Operation too long");
+
+ if(req->op == UBD_READ) {
+ for(i = 0; i < req->length >> 9; i++){
+ if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
+ ubd_set_bit(i, (unsigned char *)
+ &req->sector_mask);
+ }
+ }
+ else cowify_bitmap(req->offset, req->length, &req->sector_mask,
+ &req->cow_offset, bitmap, bitmap_offset,
+ req->bitmap_words, bitmap_len);
}
/* Called with ubd_io_lock held */
-static int prepare_request(struct request *req, struct io_thread_req *io_req,
- unsigned long long offset, int page_offset,
- int len, struct page *page)
+static int prepare_request(struct request *req, struct io_thread_req *io_req)
{
struct gendisk *disk = req->rq_disk;
struct ubd *dev = disk->private_data;
+ __u64 offset;
+ int len;
+
+ if(req->rq_status == RQ_INACTIVE) return(1);
/* This should be impossible now */
if((rq_data_dir(req) == WRITE) && !dev->openflags.w){
printk("Write attempted on readonly ubd device %s\n",
disk->disk_name);
- ubd_end_request(req, 0, 0);
+ end_request(req, 0);
return(1);
}
+ offset = ((__u64) req->sector) << 9;
+ len = req->current_nr_sectors << 9;
+
io_req->fds[0] = (dev->cow.file != NULL) ? dev->cow.fd : dev->fd;
io_req->fds[1] = dev->fd;
+ io_req->cow_offset = -1;
io_req->offset = offset;
io_req->length = len;
io_req->error = 0;
- io_req->op = (rq_data_dir(req) == READ) ? AIO_READ : AIO_WRITE;
+ io_req->sector_mask = 0;
+
+ io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
io_req->offsets[0] = 0;
io_req->offsets[1] = dev->cow.data_offset;
- io_req->buffer = page_address(page) + page_offset;
+ io_req->buffer = req->buffer;
io_req->sectorsize = 1 << 9;
- io_req->bitmap_offset = dev->cow.bitmap_offset;
- io_req->bitmap_start = -1;
- io_req->bitmap_end = -1;
- if((dev->cow.file != NULL) && (io_req->op == UBD_WRITE))
- cowify_bitmap(io_req, dev->cow.bitmap);
+ if(dev->cow.file != NULL)
+ cowify_req(io_req, dev->cow.bitmap, dev->cow.bitmap_offset,
+ dev->cow.bitmap_len);
+
return(0);
}
@@ -996,36 +1030,30 @@
{
struct io_thread_req io_req;
struct request *req;
- __u64 sector;
- int err;
+ int err, n;
- if(in_ubd)
- return;
- in_ubd = 1;
- while((req = elv_next_request(q)) != NULL){
- struct gendisk *disk = req->rq_disk;
- struct ubd *dev = disk->private_data;
- int n, i;
-
- blkdev_dequeue_request(req);
-
- sector = req->sector;
- n = blk_rq_map_sg(q, req, dev->sg);
-
- for(i = 0; i < n; i++){
- struct scatterlist *sg = &dev->sg[i];
-
- err = prepare_request(req, &io_req, sector << 9,
- sg->offset, sg->length,
- sg->page);
- if(err)
- continue;
-
- sector += sg->length >> 9;
- do_io(&io_req, req, dev->cow.bitmap);
+ if(thread_fd == -1){
+ while((req = elv_next_request(q)) != NULL){
+ err = prepare_request(req, &io_req);
+ if(!err){
+ do_io(&io_req);
+ __ubd_finish(req, io_req.error);
+ }
}
}
- in_ubd = 0;
+ else {
+ if(do_ubd || (req = elv_next_request(q)) == NULL)
+ return;
+ err = prepare_request(req, &io_req);
+ if(!err){
+ do_ubd = ubd_handler;
+ n = os_write_file(thread_fd, (char *) &io_req,
+ sizeof(io_req));
+ if(n != sizeof(io_req))
+ printk("write to io thread failed, "
+ "errno = %d\n", -n);
+ }
+ }
}
static int ubd_ioctl(struct inode * inode, struct file * file,
@@ -1241,95 +1269,131 @@
return(err);
}
-void do_io(struct io_thread_req *req, struct request *r, unsigned long *bitmap)
+static int update_bitmap(struct io_thread_req *req)
{
- struct ubd_aio *aio;
- struct bitmap_io *bitmap_io = NULL;
- char *buf;
- void *bitmap_buf = NULL;
- unsigned long len, sector;
- int nsectors, start, end, bit, err;
- __u64 off;
+ int n;
- if(req->bitmap_start != -1){
- /* Round up to the nearest word */
- int round = sizeof(unsigned long);
- len = (req->bitmap_end - req->bitmap_start +
- round * 8 - 1) / (round * 8);
- len *= round;
+ if(req->cow_offset == -1)
+ return(0);
- off = req->bitmap_start / (8 * round);
- off *= round;
+ n = os_seek_file(req->fds[1], req->cow_offset);
+ if(n < 0){
+ printk("do_io - bitmap lseek failed : err = %d\n", -n);
+ return(1);
+ }
- bitmap_io = kmalloc(sizeof(*bitmap_io), GFP_KERNEL);
- if(bitmap_io == NULL){
- printk("Failed to kmalloc bitmap IO\n");
- req->error = 1;
- return;
- }
+ n = os_write_file(req->fds[1], &req->bitmap_words,
+ sizeof(req->bitmap_words));
+ if(n != sizeof(req->bitmap_words)){
+ printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
+ req->fds[1]);
+ return(1);
+ }
- bitmap_buf = kmalloc(len, GFP_KERNEL);
- if(bitmap_buf == NULL){
- printk("do_io : kmalloc of bitmap chunk "
- "failed\n");
- kfree(bitmap_io);
- req->error = 1;
- return;
- }
- memcpy(bitmap_buf, &bitmap[off / sizeof(bitmap[0])], len);
-
- *bitmap_io = ((struct bitmap_io)
- { .count = ATOMIC_INIT(0),
- .aio = INIT_AIO(AIO_WRITE, req->fds[1],
- bitmap_buf, len,
- req->bitmap_offset + off,
- ubd_reply_fd) } );
- }
-
- nsectors = req->length / req->sectorsize;
- start = 0;
- end = nsectors;
- bit = 0;
- do {
- if(bitmap != NULL){
- sector = req->offset / req->sectorsize;
- bit = ubd_test_bit(sector + start, bitmap);
- end = start;
- while((end < nsectors) &&
- (ubd_test_bit(sector + end, bitmap) == bit))
- end++;
- }
-
- off = req->offsets[bit] + req->offset +
- start * req->sectorsize;
- len = (end - start) * req->sectorsize;
- buf = &req->buffer[start * req->sectorsize];
-
- aio = kmalloc(sizeof(*aio), GFP_KERNEL);
- if(aio == NULL){
- req->error = 1;
- return;
- }
-
- *aio = ((struct ubd_aio)
- { .aio = INIT_AIO(req->op, req->fds[bit], buf,
- len, off, ubd_reply_fd),
- .len = len,
- .req = r,
- .bitmap = bitmap_io,
- .bitmap_buf = bitmap_buf });
-
- if(aio->bitmap != NULL)
- atomic_inc(&aio->bitmap->count);
-
- err = submit_aio(&aio->aio);
- if(err){
- printk("do_io - submit_aio failed, "
- "err = %d\n", err);
- req->error = 1;
- return;
- }
-
- start = end;
- } while(start < nsectors);
+ return(0);
}
+
+void do_io(struct io_thread_req *req)
+{
+ char *buf;
+ unsigned long len;
+ int n, nsectors, start, end, bit;
+ int err;
+ __u64 off;
+
+ nsectors = req->length / req->sectorsize;
+ start = 0;
+ do {
+ bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
+ end = start;
+ while((end < nsectors) &&
+ (ubd_test_bit(end, (unsigned char *)
+ &req->sector_mask) == bit))
+ end++;
+
+ off = req->offset + req->offsets[bit] +
+ start * req->sectorsize;
+ len = (end - start) * req->sectorsize;
+ buf = &req->buffer[start * req->sectorsize];
+
+ err = os_seek_file(req->fds[bit], off);
+ if(err < 0){
+ printk("do_io - lseek failed : err = %d\n", -err);
+ req->error = 1;
+ return;
+ }
+ if(req->op == UBD_READ){
+ n = 0;
+ do {
+ buf = &buf[n];
+ len -= n;
+ n = os_read_file(req->fds[bit], buf, len);
+ if (n < 0) {
+ printk("do_io - read failed, err = %d "
+ "fd = %d\n", -n, req->fds[bit]);
+ req->error = 1;
+ return;
+ }
+ } while((n < len) && (n != 0));
+ if (n < len) memset(&buf[n], 0, len - n);
+ } else {
+ n = os_write_file(req->fds[bit], buf, len);
+ if(n != len){
+ printk("do_io - write failed err = %d "
+ "fd = %d\n", -n, req->fds[bit]);
+ req->error = 1;
+ return;
+ }
+ }
+
+ start = end;
+ } while(start < nsectors);
+
+ req->error = update_bitmap(req);
+}
+
+/* Changed in start_io_thread, which is serialized by being called only
+ * from ubd_init, which is an initcall.
+ */
+int kernel_fd = -1;
+
+/* Only changed by the io thread */
+int io_count = 0;
+
+int io_thread(void *arg)
+{
+ struct io_thread_req req;
+ int n;
+
+ ignore_sigwinch_sig();
+ while(1){
+ n = os_read_file(kernel_fd, &req, sizeof(req));
+ if(n != sizeof(req)){
+ if(n < 0)
+ printk("io_thread - read failed, fd = %d, "
+ "err = %d\n", kernel_fd, -n);
+ else {
+ printk("io_thread - short read, fd = %d, "
+ "length = %d\n", kernel_fd, n);
+ }
+ continue;
+ }
+ io_count++;
+ do_io(&req);
+ n = os_write_file(kernel_fd, &req, sizeof(req));
+ if(n != sizeof(req))
+ printk("io_thread - write failed, fd = %d, err = %d\n",
+ kernel_fd, -n);
+ }
+}
+
+/*
+ * Overrides for Emacs so that we follow Linus's tabbing style.
+ * Emacs will notice this stuff at the end of the file and automatically
+ * adjust the settings for this buffer only. This must remain at the end
+ * of the file.
+ * ---------------------------------------------------------------------------
+ * Local variables:
+ * c-file-style: "linux"
+ * End:
+ */