[PATCH] Add vector AIO support

This work is initially done by Zach Brown to add support for vectored aio.
These are the core changes for AIO to support
IOCB_CMD_PREADV/IOCB_CMD_PWRITEV.

[akpm@osdl.org: huge build fix]
Signed-off-by: Zach Brown <zach.brown@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Acked-by: Benjamin LaHaise <bcrl@kvack.org>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 117 insertions, 54 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 27ff56540c73..2e0d1505ee36 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -415,6 +415,7 @@ static struct kiocb fastcall *__aio_get_req(struct kioctx *ctx)
         req->ki_retry = NULL;
         req->ki_dtor = NULL;
         req->private = NULL;
+        req->ki_iovec = NULL;
         INIT_LIST_HEAD(&req->ki_run_list);
 
         /* Check if the completion queue has enough free space to
@@ -460,6 +461,8 @@ static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
 
         if (req->ki_dtor)
                 req->ki_dtor(req);
+        if (req->ki_iovec != &req->ki_inline_vec)
+                kfree(req->ki_iovec);
         kmem_cache_free(kiocb_cachep, req);
         ctx->reqs_active--;
 
@@ -1301,69 +1304,63 @@ asmlinkage long sys_io_destroy(aio_context_t ctx)
         return -EINVAL;
 }
 
-/*
- * aio_p{read,write} are the default  ki_retry methods for
- * IO_CMD_P{READ,WRITE}.  They maintains kiocb retry state around potentially
- * multiple calls to f_op->aio_read().  They loop around partial progress
- * instead of returning -EIOCBRETRY because they don't have the means to call
- * kick_iocb().
- */
-static ssize_t aio_pread(struct kiocb *iocb)
+static void aio_advance_iovec(struct kiocb *iocb, ssize_t ret)
 {
-        struct file *file = iocb->ki_filp;
-        struct address_space *mapping = file->f_mapping;
-        struct inode *inode = mapping->host;
-        ssize_t ret = 0;
-
-        do {
-                iocb->ki_inline_vec.iov_base = iocb->ki_buf;
-                iocb->ki_inline_vec.iov_len = iocb->ki_left;
-
-                ret = file->f_op->aio_read(iocb, &iocb->ki_inline_vec,
-                                                1, iocb->ki_pos);
-                /*
-                 * Can't just depend on iocb->ki_left to determine
-                 * whether we are done. This may have been a short read.
-                 */
-                if (ret > 0) {
-                        iocb->ki_buf += ret;
-                        iocb->ki_left -= ret;
+        struct iovec *iov = &iocb->ki_iovec[iocb->ki_cur_seg];
+
+        BUG_ON(ret <= 0);
+
+        while (iocb->ki_cur_seg < iocb->ki_nr_segs && ret > 0) {
+                ssize_t this = min((ssize_t)iov->iov_len, ret);
+                iov->iov_base += this;
+                iov->iov_len -= this;
+                iocb->ki_left -= this;
+                ret -= this;
+                if (iov->iov_len == 0) {
+                        iocb->ki_cur_seg++;
+                        iov++;
                 }
+        }
 
-                /*
-                 * For pipes and sockets we return once we have some data; for
-                 * regular files we retry till we complete the entire read or
-                 * find that we can't read any more data (e.g short reads).
-                 */
-        } while (ret > 0 && iocb->ki_left > 0 &&
-                 !S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode));
-
-        /* This means we must have transferred all that we could */
-        /* No need to retry anymore */
-        if ((ret == 0) || (iocb->ki_left == 0))
-                ret = iocb->ki_nbytes - iocb->ki_left;
-
-        return ret;
+        /* the caller should not have done more io than what fit in
+         * the remaining iovecs */
+        BUG_ON(ret > 0 && iocb->ki_left == 0);
 }
 
-/* see aio_pread() */
-static ssize_t aio_pwrite(struct kiocb *iocb)
+static ssize_t aio_rw_vect_retry(struct kiocb *iocb)
 {
         struct file *file = iocb->ki_filp;
+        struct address_space *mapping = file->f_mapping;
+        struct inode *inode = mapping->host;
+        ssize_t (*rw_op)(struct kiocb *, const struct iovec *,
+                         unsigned long, loff_t);
         ssize_t ret = 0;
+        unsigned short opcode;
+
+        if ((iocb->ki_opcode == IOCB_CMD_PREADV) ||
+                (iocb->ki_opcode == IOCB_CMD_PREAD)) {
+                rw_op = file->f_op->aio_read;
+                opcode = IOCB_CMD_PREADV;
+        } else {
+                rw_op = file->f_op->aio_write;
+                opcode = IOCB_CMD_PWRITEV;
+        }
 
         do {
-                iocb->ki_inline_vec.iov_base = iocb->ki_buf;
-                iocb->ki_inline_vec.iov_len = iocb->ki_left;
-
-                ret = file->f_op->aio_write(iocb, &iocb->ki_inline_vec,
-                                                1, iocb->ki_pos);
-                if (ret > 0) {
-                        iocb->ki_buf += ret;
-                        iocb->ki_left -= ret;
-                }
-        } while (ret > 0 && iocb->ki_left > 0);
+                ret = rw_op(iocb, &iocb->ki_iovec[iocb->ki_cur_seg],
+                            iocb->ki_nr_segs - iocb->ki_cur_seg,
+                            iocb->ki_pos);
+                if (ret > 0)
+                        aio_advance_iovec(iocb, ret);
+
+        /* retry all partial writes.  retry partial reads as long as its a
+         * regular file. */
+        } while (ret > 0 && iocb->ki_left > 0 &&
+                 (opcode == IOCB_CMD_PWRITEV ||
+                  (!S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode))));
 
+        /* This means we must have transferred all that we could */
+        /* No need to retry anymore */
         if ((ret == 0) || (iocb->ki_left == 0))
                 ret = iocb->ki_nbytes - iocb->ki_left;
 
@@ -1390,6 +1387,38 @@ static ssize_t aio_fsync(struct kiocb *iocb)
         return ret;
 }
 
+static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb)
+{
+        ssize_t ret;
+
+        ret = rw_copy_check_uvector(type, (struct iovec __user *)kiocb->ki_buf,
+                                    kiocb->ki_nbytes, 1,
+                                    &kiocb->ki_inline_vec, &kiocb->ki_iovec);
+        if (ret < 0)
+                goto out;
+
+        kiocb->ki_nr_segs = kiocb->ki_nbytes;
+        kiocb->ki_cur_seg = 0;
+        /* ki_nbytes/left now reflect bytes instead of segs */
+        kiocb->ki_nbytes = ret;
+        kiocb->ki_left = ret;
+
+        ret = 0;
+out:
+        return ret;
+}
+
+static ssize_t aio_setup_single_vector(struct kiocb *kiocb)
+{
+        kiocb->ki_iovec = &kiocb->ki_inline_vec;
+        kiocb->ki_iovec->iov_base = kiocb->ki_buf;
+        kiocb->ki_iovec->iov_len = kiocb->ki_left;
+        kiocb->ki_nr_segs = 1;
+        kiocb->ki_cur_seg = 0;
+        kiocb->ki_nbytes = kiocb->ki_left;
+        return 0;
+}
+
 /*
  * aio_setup_iocb:
  *      Performs the initial checks and aio retry method
@@ -1412,9 +1441,12 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb)
                 ret = security_file_permission(file, MAY_READ);
                 if (unlikely(ret))
                         break;
+                ret = aio_setup_single_vector(kiocb);
+                if (ret)
+                        break;
                 ret = -EINVAL;
                 if (file->f_op->aio_read)
-                        kiocb->ki_retry = aio_pread;
+                        kiocb->ki_retry = aio_rw_vect_retry;
                 break;
         case IOCB_CMD_PWRITE:
                 ret = -EBADF;
@@ -1427,9 +1459,40 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb)
                 ret = security_file_permission(file, MAY_WRITE);
                 if (unlikely(ret))
                         break;
+                ret = aio_setup_single_vector(kiocb);
+                if (ret)
+                        break;
+                ret = -EINVAL;
+                if (file->f_op->aio_write)
+                        kiocb->ki_retry = aio_rw_vect_retry;
+                break;
+        case IOCB_CMD_PREADV:
+                ret = -EBADF;
+                if (unlikely(!(file->f_mode & FMODE_READ)))
+                        break;
+                ret = security_file_permission(file, MAY_READ);
+                if (unlikely(ret))
+                        break;
+                ret = aio_setup_vectored_rw(READ, kiocb);
+                if (ret)
+                        break;
+                ret = -EINVAL;
+                if (file->f_op->aio_read)
+                        kiocb->ki_retry = aio_rw_vect_retry;
+                break;
+        case IOCB_CMD_PWRITEV:
+                ret = -EBADF;
+                if (unlikely(!(file->f_mode & FMODE_WRITE)))
+                        break;
+                ret = security_file_permission(file, MAY_WRITE);
+                if (unlikely(ret))
+                        break;
+                ret = aio_setup_vectored_rw(WRITE, kiocb);
+                if (ret)
+                        break;
                 ret = -EINVAL;
                 if (file->f_op->aio_write)
-                        kiocb->ki_retry = aio_pwrite;
+                        kiocb->ki_retry = aio_rw_vect_retry;
                 break;
         case IOCB_CMD_FDSYNC:
                 ret = -EINVAL;