From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Huaisheng Ye Subject: [RFC PATCH v2 2/3] dm: expand hc_map in mapped_device for lack of map Date: Wed, 21 Nov 2018 11:27:01 +0800 Message-Id: <20181121032702.3048-3-yehs2007@zoho.com> In-Reply-To: <20181121032702.3048-1-yehs2007@zoho.com> References: <20181121032702.3048-1-yehs2007@zoho.com> Sender: linux-fsdevel-owner@vger.kernel.org To: linux-nvdimm@lists.01.org, agk@redhat.com, snitzer@redhat.com, dm-devel@redhat.com, dan.j.williams@intel.com, willy@infradead.org, zwisler@kernel.org, jack@suse.cz, dave.jiang@intel.com, vishal.l.verma@intel.com Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, chengnt@lenovo.com, Huaisheng Ye List-ID: From: Huaisheng Ye Sometimes dm_swap_table couldn't be used in time. For example, during the origin construction of dm-snapshot, the sys_ioctl table_load will try to detect the lower device origin-real whether support direct access or not. But origin-real md's struct dm-table pointer has not yet been assigned real address in time by dev_suspend. So I expand hc_map for get the address from struct hash_cell directly in this case. Here is the call trace, dm_dax_direct_access will call dm_dax_get_live_target for get the struct dm_table pointer. [ 213.975827] Call Trace: [ 213.975832] dump_stack+0x5a/0x73 [ 213.975840] dm_dax_direct_access+0x12b/0x1b0 [dm_mod] [ 213.975845] dax_direct_access+0x2d/0x60 [ 213.975848] __bdev_dax_supported+0x162/0x2a0 [ 213.975851] ? dump_stack+0x5a/0x73 [ 213.975859] device_supports_dax+0x15/0x20 [dm_mod] [ 213.975867] dm_table_supports_dax.isra.13+0x7d/0xa0 [dm_mod] [ 213.975875] dm_table_complete+0x3fb/0x750 [dm_mod] [ 213.975883] table_load+0x19a/0x390 [dm_mod] [ 213.975891] ? retrieve_status+0x1c0/0x1c0 [dm_mod] [ 213.975898] ctl_ioctl+0x1d8/0x450 [dm_mod] [ 213.975909] dm_ctl_ioctl+0xa/0x10 [dm_mod] [ 213.975913] do_vfs_ioctl+0xa9/0x620 [ 213.975918] ? syscall_trace_enter+0x1c9/0x2b0 [ 213.975923] ksys_ioctl+0x60/0x90 [ 213.975927] __x64_sys_ioctl+0x16/0x20 [ 213.975931] do_syscall_64+0x5b/0x180 [ 213.975936] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Huaisheng Ye --- drivers/md/dm-core.h | 1 + drivers/md/dm-ioctl.c | 1 + drivers/md/dm.c | 15 +++++++++++++++ 3 files changed, 17 insertions(+) diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 224d445..5577d90 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -40,6 +40,7 @@ struct mapped_device { * dereference. */ void __rcu *map; + struct dm_table *hc_map; unsigned long flags; diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index f666778..a27016e 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1365,6 +1365,7 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si if (hc->new_map) old_map = hc->new_map; hc->new_map = t; + hc->md->hc_map = hc->new_map; up_write(&_hash_lock); param->flags |= DM_INACTIVE_PRESENT_FLAG; diff --git a/drivers/md/dm.c b/drivers/md/dm.c index c510179..19b48bb 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1080,6 +1080,21 @@ static struct dm_target *dm_dax_get_live_target(struct mapped_device *md, struct dm_target *ti; map = dm_get_live_table(md, srcu_idx); + if (!map) { + /* Sometimes dm_swap_table couldn't be used in time. + * + * For example, during the origin construction of + * dm-snapshot, the sys_ioctl table_load will try to + * detect the lower device origin-real whether support + * direct access or not. But origin-real device md's struct + * dm-table pointer has not yet been assigned real address. + * So hc_map has been used for get the address from + * struct hash_cell directly. + */ + DMINFO("failed to get map, use hc_map insteadly"); + map = md->hc_map; + } + if (!map) return NULL; -- 1.8.3.1