Messages in this thread Patch in this message | | | From | Jens Axboe <> | Subject | [PATCH 3/3] loop: support O_DIRECT transfer mode | Date | Mon, 17 Aug 2009 12:34:34 +0200 |
| |
Make use of the (now) page array backed O_DIRECT with a special transfer mode for loop.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com> --- drivers/block/loop.c | 138 +++++++++++++++++++++++++++++++++++++++++++++++++- include/linux/loop.h | 1 + 2 files changed, 138 insertions(+), 1 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 5757188..ca5b366 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -82,6 +82,9 @@ static DEFINE_MUTEX(loop_devices_mutex); static int max_part; static int part_shift; +static int odirect = 1; + +#define LOOP_MAX_DIRECT_SEGMENTS 32 /* * Transfer functions @@ -201,6 +204,123 @@ lo_do_transfer(struct loop_device *lo, int cmd, return lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock); } +static int direct_fill_pages(struct bio *bio, struct page **pages) +{ + unsigned int i, pidx = 0; + struct bio_vec *bvec; + + bio_for_each_segment(bvec, bio, i) + pages[pidx++] = bvec->bv_page; + + return pidx; +} + +/* + * Use the O_DIRECT IO path for this read + */ +static int lo_direct_read(struct loop_device *lo, struct bio *bio, loff_t pos) +{ + struct file *file = lo->lo_backing_file; + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + struct page *pages[LOOP_MAX_DIRECT_SEGMENTS]; + struct kiocb iocb; + loff_t size; + int ret = 0; + struct dio_args args = { + .pages = pages, + .length = bio->bi_size, + .user_addr = 0, + .offset = pos, + }; + + init_sync_kiocb(&iocb, file); + iocb.ki_pos = pos; + iocb.ki_left = bio->bi_size; + kiocbSetKernel(&iocb); + + args.nr_pages = direct_fill_pages(bio, pages); + args.first_page_off = bio->bi_io_vec[0].bv_offset; + + size = i_size_read(inode); + if (pos >= size) + goto out; + + ret = filemap_write_and_wait_range(mapping, pos, pos + bio->bi_size-1); + if (ret) + goto out; + + ret = mapping->a_ops->direct_IO(READ, &iocb, &args); + if (ret > 0) { + file_accessed(file); + ret = 0; + } + +out: + return ret; +} + +/* + * Use the O_DIRECT IO path for this write + */ +static int lo_direct_write(struct loop_device *lo, struct bio *bio, loff_t pos) +{ + struct file *file = lo->lo_backing_file; + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + struct page *pages[LOOP_MAX_DIRECT_SEGMENTS]; + struct kiocb iocb; + int ret = 0; + pgoff_t end; + struct dio_args args = { + .pages = pages, + .length = bio->bi_size, + .user_addr = 0, + .offset = pos, + }; + + ret = filemap_write_and_wait_range(mapping, pos, pos + bio->bi_size-1); + if (ret) + goto out; + + end = (pos + bio->bi_size - 1) >> PAGE_CACHE_SHIFT; + if (mapping->nrpages) { + ret = invalidate_inode_pages2_range(mapping, + pos >> PAGE_CACHE_SHIFT, end); + if (ret) { + if (ret == -EBUSY) + ret = 0; + goto out; + } + } + + init_sync_kiocb(&iocb, file); + iocb.ki_pos = pos; + iocb.ki_left = bio->bi_size; + kiocbSetKernel(&iocb); + + args.nr_pages = direct_fill_pages(bio, pages); + args.first_page_off = bio->bi_io_vec[0].bv_offset; + + ret = mapping->a_ops->direct_IO(WRITE, &iocb, &args); + + if (mapping->nrpages) { + invalidate_inode_pages2_range(mapping, + pos >> PAGE_CACHE_SHIFT, end); + } + + if (ret > 0) { + loff_t end = pos + ret; + if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { + i_size_write(inode, end); + mark_inode_dirty(inode); + } + ret = 0; + } +out: + return ret; +} + /** * do_lo_send_aops - helper for writing data to a loop device * @@ -347,6 +467,9 @@ static int lo_send(struct loop_device *lo, struct bio *bio, loff_t pos) struct page *page = NULL; int i, ret = 0; + if (lo->lo_flags & LO_FLAGS_ODIRECT) + return lo_direct_write(lo, bio, pos); + do_lo_send = do_lo_send_aops; if (!(lo->lo_flags & LO_FLAGS_USE_AOPS)) { do_lo_send = do_lo_send_direct_write; @@ -458,6 +581,9 @@ lo_receive(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos) struct bio_vec *bvec; int i, ret = 0; + if (lo->lo_flags & LO_FLAGS_ODIRECT) + return lo_direct_read(lo, bio, pos); + bio_for_each_segment(bvec, bio, i) { ret = do_lo_receive(lo, bvec, bsize, pos); if (ret < 0) @@ -784,7 +910,11 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, if (S_ISREG(inode->i_mode) || S_ISBLK(inode->i_mode)) { const struct address_space_operations *aops = mapping->a_ops; - if (aops->write_begin) + if (odirect) { + if (!aops->direct_IO) + goto out_putf; + lo_flags |= LO_FLAGS_ODIRECT; + } else if (aops->write_begin) lo_flags |= LO_FLAGS_USE_AOPS; if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write) lo_flags |= LO_FLAGS_READ_ONLY; @@ -831,6 +961,10 @@ 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_ordered(lo->lo_queue, QUEUE_ORDERED_DRAIN, NULL); + if (odirect) { + blk_queue_max_phys_segments(lo->lo_queue, LOOP_MAX_DIRECT_SEGMENTS); + blk_queue_max_hw_segments(lo->lo_queue, LOOP_MAX_DIRECT_SEGMENTS); + } set_capacity(lo->lo_disk, size); bd_set_size(bdev, size << 9); @@ -1456,6 +1590,8 @@ module_param(max_loop, int, 0); MODULE_PARM_DESC(max_loop, "Maximum number of loop devices"); module_param(max_part, int, 0); MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device"); +module_param(odirect, int, 0); +MODULE_PARM_DESC(odirect, "Use O_DIRECT for IO"); MODULE_LICENSE("GPL"); MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR); diff --git a/include/linux/loop.h b/include/linux/loop.h index 66c194e..a7433c0 100644 --- a/include/linux/loop.h +++ b/include/linux/loop.h @@ -76,6 +76,7 @@ enum { LO_FLAGS_READ_ONLY = 1, LO_FLAGS_USE_AOPS = 2, LO_FLAGS_AUTOCLEAR = 4, + LO_FLAGS_ODIRECT = 8, }; #include <asm/posix_types.h> /* for __kernel_old_dev_t */ -- 1.6.4.53.g3f55e
| |