From: Ross Zwisler Subject: [PATCH 2/2] dm log writes: add support for DAX Date: Thu, 19 Oct 2017 23:24:04 -0600 Message-ID: <20171020052404.13762-2-ross.zwisler@linux.intel.com> References: <20171020052404.13762-1-ross.zwisler@linux.intel.com> Cc: Ross Zwisler , Alasdair Kergon , Dan Williams , Dave Chinner , Jan Kara , Mike Snitzer , Shaohua Li , dm-devel@redhat.com, linux-nvdimm@lists.01.org, linux-raid@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, Christoph Hellwig To: linux-kernel@vger.kernel.org, Josef Bacik Return-path: In-Reply-To: <20171020052404.13762-1-ross.zwisler@linux.intel.com> Sender: linux-raid-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Now that we have the ability log filesystem writes using a flat buffer, add support for DAX. Unfortunately we can't easily track data that has been written via mmap() now that the dax_flush() abstraction was removed by this commit: commit c3ca015fab6d ("dax: remove the pmem_dax_ops->flush abstraction") Otherwise we could just treat each flush as a big write, and store the data that is being synced to media. It may be worthwhile to add the dax_flush() entry point back, just as a notifier so we can do this logging. The motivation for this support is the need for an xfstest that can test the new MAP_SYNC DAX flag. By logging the filesystem activity with dm-log-writes we can show that the MAP_SYNC page faults are writing out their metadata as they happen, instead of requiring an explicit msync/fsync. Signed-off-by: Ross Zwisler --- Here's a link to Jan's latest MAP_SYNC set, which can be used for the fstest: https://www.spinics.net/lists/linux-xfs/msg11852.html MAP_SYNC is not needed for basic DAX+dm-log-writes functionality. --- drivers/md/dm-log-writes.c | 90 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 89 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c index c65f9d1..6a8d352 100644 --- a/drivers/md/dm-log-writes.c +++ b/drivers/md/dm-log-writes.c @@ -10,9 +10,11 @@ #include #include #include +#include #include #include #include +#include #define DM_MSG_PREFIX "log-writes" @@ -609,6 +611,50 @@ static int log_mark(struct log_writes_c *lc, char *data) return 0; } +static int log_dax(struct log_writes_c *lc, sector_t sector, size_t bytes, + struct iov_iter *i) +{ + struct pending_block *block; + + if (!bytes) + return 0; + + block = kzalloc(sizeof(struct pending_block), GFP_KERNEL); + if (!block) { + DMERR("Error allocating dax pending block"); + return -ENOMEM; + } + + block->data = kzalloc(bytes, GFP_KERNEL); + if (!block->data) { + DMERR("Error allocating dax data space"); + kfree(block); + return -ENOMEM; + } + + /* write data provided via the iterator */ + if (!copy_from_iter(block->data, bytes, i)) { + DMERR("Error copying dax data"); + kfree(block->data); + kfree(block); + return -EIO; + } + + /* rewind the iterator so that the block driver can use it */ + iov_iter_revert(i, bytes); + + block->datalen = bytes; + block->sector = bio_to_dev_sectors(lc, sector); + block->nr_sectors = ALIGN(bytes, lc->sectorsize) >> lc->sectorshift; + + atomic_inc(&lc->pending_blocks); + spin_lock_irq(&lc->blocks_lock); + list_add_tail(&block->list, &lc->unflushed_blocks); + spin_unlock_irq(&lc->blocks_lock); + wake_up_process(lc->log_kthread); + return 0; +} + static void log_writes_dtr(struct dm_target *ti) { struct log_writes_c *lc = ti->private; @@ -874,9 +920,49 @@ static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limit limits->io_min = limits->physical_block_size; } +static long log_writes_dax_direct_access(struct dm_target *ti, pgoff_t pgoff, + long nr_pages, void **kaddr, pfn_t *pfn) +{ + struct log_writes_c *lc = ti->private; + struct block_device *bdev = lc->dev->bdev; + struct dax_device *dax_dev = lc->dev->dax_dev; + sector_t sector = pgoff * PAGE_SECTORS; + int ret; + + ret = bdev_dax_pgoff(bdev, sector, nr_pages * PAGE_SIZE, &pgoff); + if (ret) + return ret; + return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn); +} + +static size_t log_writes_dax_copy_from_iter(struct dm_target *ti, + pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i) +{ + struct log_writes_c *lc = ti->private; + struct block_device *bdev = lc->dev->bdev; + struct dax_device *dax_dev = lc->dev->dax_dev; + sector_t sector = pgoff * PAGE_SECTORS; + int err; + + if (bdev_dax_pgoff(bdev, sector, ALIGN(bytes, PAGE_SIZE), &pgoff)) + return 0; + + /* Don't bother doing anything if logging has been disabled */ + if (!lc->logging_enabled) + goto dax_copy; + + err = log_dax(lc, sector, bytes, i); + if (err) { + DMWARN("Error %d logging DAX write", err); + return 0; + } +dax_copy: + return dax_copy_from_iter(dax_dev, pgoff, addr, bytes, i); +} + static struct target_type log_writes_target = { .name = "log-writes", - .version = {1, 0, 0}, + .version = {1, 0, 1}, .module = THIS_MODULE, .ctr = log_writes_ctr, .dtr = log_writes_dtr, @@ -887,6 +973,8 @@ static struct target_type log_writes_target = { .message = log_writes_message, .iterate_devices = log_writes_iterate_devices, .io_hints = log_writes_io_hints, + .direct_access = log_writes_dax_direct_access, + .dax_copy_from_iter = log_writes_dax_copy_from_iter, }; static int __init dm_log_writes_init(void) -- 2.9.5