diff options
| -rw-r--r-- | fs/aio.c | 79 | ||||
| -rw-r--r-- | include/linux/aio.h | 34 |
2 files changed, 67 insertions, 46 deletions
@@ -741,19 +741,9 @@ static ssize_t aio_run_iocb(struct kiocb *iocb) ret = retry(iocb); current->io_wait = NULL; - if (-EIOCBRETRY != ret) { - if (-EIOCBQUEUED != ret) { - BUG_ON(!list_empty(&iocb->ki_wait.task_list)); - aio_complete(iocb, ret, 0); - /* must not access the iocb after this */ - } - } else { - /* - * Issue an additional retry to avoid waiting forever if - * no waits were queued (e.g. in case of a short read). - */ - if (list_empty(&iocb->ki_wait.task_list)) - kiocbSetKicked(iocb); + if (ret != -EIOCBRETRY && ret != -EIOCBQUEUED) { + BUG_ON(!list_empty(&iocb->ki_wait.task_list)); + aio_complete(iocb, ret, 0); } out: spin_lock_irq(&ctx->ctx_lock); @@ -1327,8 +1317,11 @@ asmlinkage long sys_io_destroy(aio_context_t ctx) } /* - * Default retry method for aio_read (also used for first time submit) - * Responsible for updating iocb state as retries progress + * 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) { @@ -1337,25 +1330,25 @@ static ssize_t aio_pread(struct kiocb *iocb) struct inode *inode = mapping->host; ssize_t ret = 0; - ret = file->f_op->aio_read(iocb, iocb->ki_buf, - iocb->ki_left, iocb->ki_pos); + do { + ret = file->f_op->aio_read(iocb, iocb->ki_buf, + iocb->ki_left, 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; + } - /* - * 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; /* - * 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). + * 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). */ - if (!S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode)) - ret = -EIOCBRETRY; - } + } while (ret > 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 */ @@ -1365,27 +1358,21 @@ static ssize_t aio_pread(struct kiocb *iocb) return ret; } -/* - * Default retry method for aio_write (also used for first time submit) - * Responsible for updating iocb state as retries progress - */ +/* see aio_pread() */ static ssize_t aio_pwrite(struct kiocb *iocb) { struct file *file = iocb->ki_filp; ssize_t ret = 0; - ret = file->f_op->aio_write(iocb, iocb->ki_buf, - iocb->ki_left, iocb->ki_pos); - - if (ret > 0) { - iocb->ki_buf += ret; - iocb->ki_left -= ret; - - ret = -EIOCBRETRY; - } + do { + ret = file->f_op->aio_write(iocb, iocb->ki_buf, + iocb->ki_left, iocb->ki_pos); + if (ret > 0) { + iocb->ki_buf += ret; + iocb->ki_left -= ret; + } + } while (ret > 0); - /* 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; diff --git a/include/linux/aio.h b/include/linux/aio.h index a4d5af907f9..60def658b24 100644 --- a/include/linux/aio.h +++ b/include/linux/aio.h @@ -43,6 +43,40 @@ struct kioctx; #define kiocbIsKicked(iocb) test_bit(KIF_KICKED, &(iocb)->ki_flags) #define kiocbIsCancelled(iocb) test_bit(KIF_CANCELLED, &(iocb)->ki_flags) +/* is there a better place to document function pointer methods? */ +/** + * ki_retry - iocb forward progress callback + * @kiocb: The kiocb struct to advance by performing an operation. + * + * This callback is called when the AIO core wants a given AIO operation + * to make forward progress. The kiocb argument describes the operation + * that is to be performed. As the operation proceeds, perhaps partially, + * ki_retry is expected to update the kiocb with progress made. Typically + * ki_retry is set in the AIO core and it itself calls file_operations + * helpers. + * + * ki_retry's return value determines when the AIO operation is completed + * and an event is generated in the AIO event ring. Except the special + * return values described below, the value that is returned from ki_retry + * is transferred directly into the completion ring as the operation's + * resulting status. Once this has happened ki_retry *MUST NOT* reference + * the kiocb pointer again. + * + * If ki_retry returns -EIOCBQUEUED it has made a promise that aio_complete() + * will be called on the kiocb pointer in the future. The AIO core will + * not ask the method again -- ki_retry must ensure forward progress. + * aio_complete() must be called once and only once in the future, multiple + * calls may result in undefined behaviour. + * + * If ki_retry returns -EIOCBRETRY it has made a promise that kick_iocb() + * will be called on the kiocb pointer in the future. This may happen + * through generic helpers that associate kiocb->ki_wait with a wait + * queue head that ki_retry uses via current->io_wait. It can also happen + * with custom tracking and manual calls to kick_iocb(), though that is + * discouraged. In either case, kick_iocb() must be called once and only + * once. ki_retry must ensure forward progress, the AIO core will wait + * indefinitely for kick_iocb() to be called. + */ struct kiocb { struct list_head ki_run_list; long ki_flags; |