Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755404AbbG3LiV (ORCPT ); Thu, 30 Jul 2015 07:38:21 -0400 Received: from mail-pa0-f47.google.com ([209.85.220.47]:36172 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753378AbbG3Lgy (ORCPT ); Thu, 30 Jul 2015 07:36:54 -0400 From: Ming Lei To: Jens Axboe , linux-kernel@vger.kernel.org, Dave Kleikamp Cc: Zach Brown , Christoph Hellwig , Maxim Patlasov , Andrew Morton , Alexander Viro , Tejun Heo , Dave Chinner , Ming Lei , linux-api@vger.kernel.org Subject: [PATCH v8 4/6] block: loop: prepare for supporing direct IO Date: Thu, 30 Jul 2015 07:36:22 -0400 Message-Id: <1438256184-23645-5-git-send-email-ming.lei@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1438256184-23645-1-git-send-email-ming.lei@canonical.com> References: <1438256184-23645-1-git-send-email-ming.lei@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5203 Lines: 176 This patches provides one interface for enabling direct IO from user space: - userspace(such as losetup) can pass 'file' which is opened/fcntl as O_DIRECT Also __loop_update_dio() is introduced to check if direct I/O can be used on current loop setting. The last big change is to introduce LO_FLAGS_DIRECT_IO flag for userspace to know if direct IO is used to access backing file. Cc: linux-api@vger.kernel.org Signed-off-by: Ming Lei --- drivers/block/loop.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++- drivers/block/loop.h | 2 ++ include/uapi/linux/loop.h | 1 + 3 files changed, 65 insertions(+), 1 deletion(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 1875aad..799cc23 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -164,6 +164,47 @@ static loff_t get_loop_size(struct loop_device *lo, struct file *file) return get_size(lo->lo_offset, lo->lo_sizelimit, file); } +static void __loop_update_dio(struct loop_device *lo, bool dio) +{ + struct file *file = lo->lo_backing_file; + struct inode *inode = file->f_mapping->host; + bool use_dio; + unsigned dio_align = inode->i_sb->s_bdev ? + (bdev_io_min(inode->i_sb->s_bdev) - 1) : 0; + + /* + * We support direct I/O only if lo_offset is aligned + * with the min I/O size of backing device. + * + * Request's offset and size will be checked in I/O path. + */ + if (dio) { + if (!dio_align || (lo->lo_offset & dio_align)) + use_dio = false; + else + use_dio = true; + } else { + use_dio = false; + } + + /* flush dirty pages before changing direct IO */ + vfs_fsync(file, 0); + + /* + * The flag of LO_FLAGS_DIRECT_IO is handled similarly with + * LO_FLAGS_READ_ONLY, both are set from kernel, and losetup + * will get updated by ioctl(LOOP_GET_STATUS) + */ + blk_mq_freeze_queue(lo->lo_queue); + lo->use_dio = use_dio; + lo->dio_align = dio_align; + if (use_dio) + lo->lo_flags |= LO_FLAGS_DIRECT_IO; + else + lo->lo_flags &= ~LO_FLAGS_DIRECT_IO; + blk_mq_unfreeze_queue(lo->lo_queue); +} + static int figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit) { @@ -173,8 +214,12 @@ figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit) if (unlikely((loff_t)x != size)) return -EFBIG; - if (lo->lo_offset != offset) + if (lo->lo_offset != offset) { lo->lo_offset = offset; + + /* update dio if lo_offset is changed*/ + __loop_update_dio(lo, lo->use_dio); + } if (lo->lo_sizelimit != sizelimit) lo->lo_sizelimit = sizelimit; set_capacity(lo->lo_disk, x); @@ -421,6 +466,11 @@ struct switch_request { struct completion wait; }; +static inline void loop_update_dio(struct loop_device *lo) +{ + __loop_update_dio(lo, io_is_direct(lo->lo_backing_file)); +} + /* * Do the actual switch; called from the BIO completion routine */ @@ -441,6 +491,7 @@ static void do_loop_switch(struct loop_device *lo, struct switch_request *p) mapping->host->i_bdev->bd_block_size : PAGE_SIZE; lo->old_gfp_mask = mapping_gfp_mask(mapping); mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS)); + loop_update_dio(lo); } /* @@ -627,11 +678,19 @@ static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf) return sprintf(buf, "%s\n", partscan ? "1" : "0"); } +static ssize_t loop_attr_dio_show(struct loop_device *lo, char *buf) +{ + int dio = (lo->lo_flags & LO_FLAGS_DIRECT_IO); + + return sprintf(buf, "%s\n", dio ? "1" : "0"); +} + LOOP_ATTR_RO(backing_file); LOOP_ATTR_RO(offset); LOOP_ATTR_RO(sizelimit); LOOP_ATTR_RO(autoclear); LOOP_ATTR_RO(partscan); +LOOP_ATTR_RO(dio); static struct attribute *loop_attrs[] = { &loop_attr_backing_file.attr, @@ -639,6 +698,7 @@ static struct attribute *loop_attrs[] = { &loop_attr_sizelimit.attr, &loop_attr_autoclear.attr, &loop_attr_partscan.attr, + &loop_attr_dio.attr, NULL, }; @@ -783,6 +843,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync) blk_queue_flush(lo->lo_queue, REQ_FLUSH); + loop_update_dio(lo); set_capacity(lo->lo_disk, size); bd_set_size(bdev, size << 9); loop_sysfs_init(lo); diff --git a/drivers/block/loop.h b/drivers/block/loop.h index b6c7d21..63f8e14 100644 --- a/drivers/block/loop.h +++ b/drivers/block/loop.h @@ -58,6 +58,8 @@ struct loop_device { struct mutex lo_ctl_mutex; struct kthread_worker worker; struct task_struct *worker_task; + unsigned dio_align; + bool use_dio; struct request_queue *lo_queue; struct blk_mq_tag_set tag_set; diff --git a/include/uapi/linux/loop.h b/include/uapi/linux/loop.h index e0cecd2..949851c 100644 --- a/include/uapi/linux/loop.h +++ b/include/uapi/linux/loop.h @@ -21,6 +21,7 @@ enum { LO_FLAGS_READ_ONLY = 1, LO_FLAGS_AUTOCLEAR = 4, LO_FLAGS_PARTSCAN = 8, + LO_FLAGS_DIRECT_IO = 16, }; #include /* for __kernel_old_dev_t */ -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/