[PATCH] uml: add host AIO support to block driver

This adds AIO support to the ubd driver.

The driver breaks a struct request into IO requests to the host, based on the
hardware segments in the request and on any COW blocks covered by the request.

The ubd IO thread is gone, since there is now an equivalent thread in the AIO
module.

There is provision for multiple outstanding requests now.  Requests aren't
retired until all pieces of it have been completed.  The AIO requests have a
shared count, which is decremented as IO operations come in until it reaches
0.  This can be possibly moved to the request struct - haven't looked at this
yet.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 111 insertions, 95 deletions

diff --git a/arch/um/os-Linux/aio.c b/arch/um/os-Linux/aio.c
index f2ca2992bbd6..b04897cd995d 100644
--- a/arch/um/os-Linux/aio.c
+++ b/arch/um/os-Linux/aio.c
@@ -6,6 +6,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <signal.h>
+#include <string.h>
 #include <errno.h>
 #include <sched.h>
 #include <sys/syscall.h>
@@ -16,18 +17,31 @@
 #include "user.h"
 #include "mode.h"
 
-struct aio_thread_req {
-        enum aio_type type;
-        int io_fd;
-        unsigned long long offset;
-        char *buf;
-        int len;
-        struct aio_context *aio;
-};
-
 static int aio_req_fd_r = -1;
 static int aio_req_fd_w = -1;
 
+static int update_aio(struct aio_context *aio, int res)
+{
+        if(res < 0)
+                aio->len = res;
+        else if((res == 0) && (aio->type == AIO_READ)){
+                /* This is the EOF case - we have hit the end of the file
+                 * and it ends in a partial block, so we fill the end of
+                 * the block with zeros and claim success.
+                 */
+                memset(aio->data, 0, aio->len);
+                aio->len = 0;
+        }
+        else if(res > 0){
+                aio->len -= res;
+                aio->data += res;
+                aio->offset += res;
+                return aio->len;
+        }
+
+        return 0;
+}
+
 #if defined(HAVE_AIO_ABI)
 #include <linux/aio_abi.h>
 
@@ -66,8 +80,7 @@ static long io_getevents(aio_context_t ctx_id, long min_nr, long nr,
  * that it now backs the mmapped area.
  */
 
-static int do_aio(aio_context_t ctx, enum aio_type type, int fd, char *buf,
-                  int len, unsigned long long offset, struct aio_context *aio)
+static int do_aio(aio_context_t ctx, struct aio_context *aio)
 {
         struct iocb iocb, *iocbp = &iocb;
         char c;
@@ -75,37 +88,37 @@ static int do_aio(aio_context_t ctx, enum aio_type type, int fd, char *buf,
 
         iocb = ((struct iocb) { .aio_data       = (unsigned long) aio,
                                 .aio_reqprio    = 0,
-                                .aio_fildes     = fd,
-                                .aio_buf        = (unsigned long) buf,
-                                .aio_nbytes     = len,
-                                .aio_offset     = offset,
+                                .aio_fildes     = aio->fd,
+                                .aio_buf        = (unsigned long) aio->data,
+                                .aio_nbytes     = aio->len,
+                                .aio_offset     = aio->offset,
                                 .aio_reserved1  = 0,
                                 .aio_reserved2  = 0,
                                 .aio_reserved3  = 0 });
 
-        switch(type){
+        switch(aio->type){
         case AIO_READ:
                 iocb.aio_lio_opcode = IOCB_CMD_PREAD;
-                err = io_submit(ctx, 1, &iocbp);
                 break;
         case AIO_WRITE:
                 iocb.aio_lio_opcode = IOCB_CMD_PWRITE;
-                err = io_submit(ctx, 1, &iocbp);
                 break;
         case AIO_MMAP:
                 iocb.aio_lio_opcode = IOCB_CMD_PREAD;
                 iocb.aio_buf = (unsigned long) &c;
                 iocb.aio_nbytes = sizeof(c);
-                err = io_submit(ctx, 1, &iocbp);
                 break;
         default:
-                printk("Bogus op in do_aio - %d\n", type);
+                printk("Bogus op in do_aio - %d\n", aio->type);
                 err = -EINVAL;
-                break;
+                goto out;
         }
+
+        err = io_submit(ctx, 1, &iocbp);
         if(err > 0)
                 err = 0;
 
+ out:
         return err;
 }
 
@@ -114,8 +127,9 @@ static aio_context_t ctx = 0;
 static int aio_thread(void *arg)
 {
         struct aio_thread_reply reply;
+        struct aio_context *aio;
         struct io_event event;
-        int err, n, reply_fd;
+        int err, n;
 
         signal(SIGWINCH, SIG_IGN);
 
@@ -128,15 +142,21 @@ static int aio_thread(void *arg)
                                "errno = %d\n", errno);
                 }
                 else {
+                        aio = (struct aio_context *) event.data;
+                        if(update_aio(aio, event.res)){
+                                do_aio(ctx, aio);
+                                continue;
+                        }
+
                         reply = ((struct aio_thread_reply)
-                                { .data = (void *) (long) event.data,
-                                  .err  = event.res });
-                        reply_fd = ((struct aio_context *) reply.data)->reply_fd;
-                        err = os_write_file(reply_fd, &reply, sizeof(reply));
+                                { .data = aio,
+                                  .err  = aio->len });
+                        err = os_write_file(aio->reply_fd, &reply,
+                                            sizeof(reply));
                         if(err != sizeof(reply))
-                                printk("not_aio_thread - write failed, "
-                                       "fd = %d, err = %d\n",
-                                       aio_req_fd_r, -err);
+                                printk("aio_thread - write failed, "
+                                       "fd = %d, err = %d\n", aio->reply_fd,
+                                       -err);
                 }
         }
         return 0;
@@ -144,35 +164,35 @@ static int aio_thread(void *arg)
 
 #endif
 
-static int do_not_aio(struct aio_thread_req *req)
+static int do_not_aio(struct aio_context *aio)
 {
         char c;
         int err;
 
-        switch(req->type){
+        switch(aio->type){
         case AIO_READ:
-                err = os_seek_file(req->io_fd, req->offset);
+                err = os_seek_file(aio->fd, aio->offset);
                 if(err)
                         goto out;
 
-                err = os_read_file(req->io_fd, req->buf, req->len);
+                err = os_read_file(aio->fd, aio->data, aio->len);
                 break;
         case AIO_WRITE:
-                err = os_seek_file(req->io_fd, req->offset);
+                err = os_seek_file(aio->fd, aio->offset);
                 if(err)
                         goto out;
 
-                err = os_write_file(req->io_fd, req->buf, req->len);
+                err = os_write_file(aio->fd, aio->data, aio->len);
                 break;
         case AIO_MMAP:
-                err = os_seek_file(req->io_fd, req->offset);
+                err = os_seek_file(aio->fd, aio->offset);
                 if(err)
                         goto out;
 
-                err = os_read_file(req->io_fd, &c, sizeof(c));
+                err = os_read_file(aio->fd, &c, sizeof(c));
                 break;
         default:
-                printk("do_not_aio - bad request type : %d\n", req->type);
+                printk("do_not_aio - bad request type : %d\n", aio->type);
                 err = -EINVAL;
                 break;
         }
@@ -183,14 +203,14 @@ static int do_not_aio(struct aio_thread_req *req)
 
 static int not_aio_thread(void *arg)
 {
-        struct aio_thread_req req;
+        struct aio_context *aio;
         struct aio_thread_reply reply;
         int err;
 
         signal(SIGWINCH, SIG_IGN);
         while(1){
-                err = os_read_file(aio_req_fd_r, &req, sizeof(req));
-                if(err != sizeof(req)){
+                err = os_read_file(aio_req_fd_r, &aio, sizeof(aio));
+                if(err != sizeof(aio)){
                         if(err < 0)
                                 printk("not_aio_thread - read failed, "
                                        "fd = %d, err = %d\n", aio_req_fd_r,
@@ -201,17 +221,34 @@ static int not_aio_thread(void *arg)
                         }
                         continue;
                 }
-                err = do_not_aio(&req);
-                reply = ((struct aio_thread_reply) { .data      = req.aio,
-                                                     .err       = err });
-                err = os_write_file(req.aio->reply_fd, &reply, sizeof(reply));
+ again:
+                err = do_not_aio(aio);
+
+                if(update_aio(aio, err))
+                        goto again;
+
+                reply = ((struct aio_thread_reply) { .data      = aio,
+                                                     .err       = aio->len });
+                err = os_write_file(aio->reply_fd, &reply, sizeof(reply));
                 if(err != sizeof(reply))
                         printk("not_aio_thread - write failed, fd = %d, "
                                "err = %d\n", aio_req_fd_r, -err);
         }
 }
 
+static int submit_aio_24(struct aio_context *aio)
+{
+        int err;
+
+        err = os_write_file(aio_req_fd_w, &aio, sizeof(aio));
+        if(err == sizeof(aio))
+                err = 0;
+
+        return err;
+}
+
 static int aio_pid = -1;
+static int (*submit_proc)(struct aio_context *aio);
 
 static int init_aio_24(void)
 {
@@ -243,11 +280,33 @@ static int init_aio_24(void)
 #endif
         printk("2.6 host AIO support not used - falling back to I/O "
                "thread\n");
+
+        submit_proc = submit_aio_24;
+
         return 0;
 }
 
 #ifdef HAVE_AIO_ABI
 #define DEFAULT_24_AIO 0
+static int submit_aio_26(struct aio_context *aio)
+{
+        struct aio_thread_reply reply;
+        int err;
+
+        err = do_aio(ctx, aio);
+        if(err){
+                reply = ((struct aio_thread_reply) { .data = aio,
+                                                     .err  = err });
+                err = os_write_file(aio->reply_fd, &reply, sizeof(reply));
+                if(err != sizeof(reply))
+                        printk("submit_aio_26 - write failed, "
+                               "fd = %d, err = %d\n", aio->reply_fd, -err);
+                else err = 0;
+        }
+
+        return err;
+}
+
 static int init_aio_26(void)
 {
         unsigned long stack;
@@ -267,39 +326,22 @@ static int init_aio_26(void)
         aio_pid = err;
 
         printk("Using 2.6 host AIO\n");
-        return 0;
-}
-
-static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
-                         unsigned long long offset, struct aio_context *aio)
-{
-        struct aio_thread_reply reply;
-        int err;
 
-        err = do_aio(ctx, type, io_fd, buf, len, offset, aio);
-        if(err){
-                reply = ((struct aio_thread_reply) { .data = aio,
-                                                     .err  = err });
-                err = os_write_file(aio->reply_fd, &reply, sizeof(reply));
-                if(err != sizeof(reply))
-                        printk("submit_aio_26 - write failed, "
-                               "fd = %d, err = %d\n", aio->reply_fd, -err);
-                else err = 0;
-        }
+        submit_proc = submit_aio_26;
 
-        return err;
+        return 0;
 }
 
 #else
 #define DEFAULT_24_AIO 1
-static int init_aio_26(void)
+static int submit_aio_26(struct aio_context *aio)
 {
         return -ENOSYS;
 }
 
-static int submit_aio_26(enum aio_type type, int io_fd, char *buf, int len,
-                         unsigned long long offset, struct aio_context *aio)
+static int init_aio_26(void)
 {
+        submit_proc = submit_aio_26;
         return -ENOSYS;
 }
 #endif
@@ -366,33 +408,7 @@ static void exit_aio(void)
 
 __uml_exitcall(exit_aio);
 
-static int submit_aio_24(enum aio_type type, int io_fd, char *buf, int len,
-                         unsigned long long offset, struct aio_context *aio)
+int submit_aio(struct aio_context *aio)
 {
-        struct aio_thread_req req = { .type             = type,
-                                      .io_fd            = io_fd,
-                                      .offset           = offset,
-                                      .buf              = buf,
-                                      .len              = len,
-                                      .aio              = aio,
-        };
-        int err;
-
-        err = os_write_file(aio_req_fd_w, &req, sizeof(req));
-        if(err == sizeof(req))
-                err = 0;
-
-        return err;
-}
-
-int submit_aio(enum aio_type type, int io_fd, char *buf, int len,
-               unsigned long long offset, int reply_fd,
-               struct aio_context *aio)
-{
-        aio->reply_fd = reply_fd;
-        if(aio_24)
-                return submit_aio_24(type, io_fd, buf, len, offset, aio);
-        else {
-                return submit_aio_26(type, io_fd, buf, len, offset, aio);
-        }
+        return (*submit_proc)(aio);
 }