On Wed, Aug 03, 2022 at 02:43:20AM +0000, ruansy.f...@fujitsu.com wrote: > > 在 2022/7/19 6:56, Dan Williams 写道: > > Darrick J. Wong wrote: > >> On Thu, Jul 14, 2022 at 11:21:44AM -0700, Dan Williams wrote: > >>> ruansy.f...@fujitsu.com wrote: > >>>> This patch is inspired by Dan's "mm, dax, pmem: Introduce > >>>> dev_pagemap_failure()"[1]. With the help of dax_holder and > >>>> ->notify_failure() mechanism, the pmem driver is able to ask filesystem > >>>> (or mapped device) on it to unmap all files in use and notify processes > >>>> who are using those files. > >>>> > >>>> Call trace: > >>>> trigger unbind > >>>> -> unbind_store() > >>>> -> ... (skip) > >>>> -> devres_release_all() # was pmem driver ->remove() in v1 > >>>> -> kill_dax() > >>>> -> dax_holder_notify_failure(dax_dev, 0, U64_MAX, > >>>> MF_MEM_PRE_REMOVE) > >>>> -> xfs_dax_notify_failure() > >>>> > >>>> Introduce MF_MEM_PRE_REMOVE to let filesystem know this is a remove > >>>> event. So do not shutdown filesystem directly if something not > >>>> supported, or if failure range includes metadata area. Make sure all > >>>> files and processes are handled correctly. > >>>> > >>>> == > >>>> Changes since v5: > >>>> 1. Renamed MF_MEM_REMOVE to MF_MEM_PRE_REMOVE > >>>> 2. hold s_umount before sync_filesystem() > >>>> 3. move sync_filesystem() after SB_BORN check > >>>> 4. Rebased on next-20220714 > >>>> > >>>> Changes since v4: > >>>> 1. sync_filesystem() at the beginning when MF_MEM_REMOVE > >>>> 2. Rebased on next-20220706 > >>>> > >>>> [1]: > >>>> https://lore.kernel.org/linux-mm/161604050314.1463742.14151665140035795571.st...@dwillia2-desk3.amr.corp.intel.com/ > >>>> > >>>> Signed-off-by: Shiyang Ruan <ruansy.f...@fujitsu.com> > >>>> --- > >>>> drivers/dax/super.c | 3 ++- > >>>> fs/xfs/xfs_notify_failure.c | 15 +++++++++++++++ > >>>> include/linux/mm.h | 1 + > >>>> 3 files changed, 18 insertions(+), 1 deletion(-) > >>>> > >>>> diff --git a/drivers/dax/super.c b/drivers/dax/super.c > >>>> index 9b5e2a5eb0ae..cf9a64563fbe 100644 > >>>> --- a/drivers/dax/super.c > >>>> +++ b/drivers/dax/super.c > >>>> @@ -323,7 +323,8 @@ void kill_dax(struct dax_device *dax_dev) > >>>> return; > >>>> > >>>> if (dax_dev->holder_data != NULL) > >>>> - dax_holder_notify_failure(dax_dev, 0, U64_MAX, 0); > >>>> + dax_holder_notify_failure(dax_dev, 0, U64_MAX, > >>>> + MF_MEM_PRE_REMOVE); > >>>> > >>>> clear_bit(DAXDEV_ALIVE, &dax_dev->flags); > >>>> synchronize_srcu(&dax_srcu); > >>>> diff --git a/fs/xfs/xfs_notify_failure.c b/fs/xfs/xfs_notify_failure.c > >>>> index 69d9c83ea4b2..6da6747435eb 100644 > >>>> --- a/fs/xfs/xfs_notify_failure.c > >>>> +++ b/fs/xfs/xfs_notify_failure.c > >>>> @@ -76,6 +76,9 @@ xfs_dax_failure_fn( > >>>> > >>>> if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) || > >>>> (rec->rm_flags & (XFS_RMAP_ATTR_FORK | > >>>> XFS_RMAP_BMBT_BLOCK))) { > >>>> + /* Do not shutdown so early when device is to be > >>>> removed */ > >>>> + if (notify->mf_flags & MF_MEM_PRE_REMOVE) > >>>> + return 0; > >>>> xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_ONDISK); > >>>> return -EFSCORRUPTED; > >>>> } > >>>> @@ -174,12 +177,22 @@ xfs_dax_notify_failure( > >>>> struct xfs_mount *mp = dax_holder(dax_dev); > >>>> u64 ddev_start; > >>>> u64 ddev_end; > >>>> + int error; > >>>> > >>>> if (!(mp->m_sb.sb_flags & SB_BORN)) { > >>>> xfs_warn(mp, "filesystem is not ready for > >>>> notify_failure()!"); > >>>> return -EIO; > >>>> } > >>>> > >>>> + if (mf_flags & MF_MEM_PRE_REMOVE) { > >>>> + xfs_info(mp, "device is about to be removed!"); > >>>> + down_write(&mp->m_super->s_umount); > >>>> + error = sync_filesystem(mp->m_super); > >>>> + up_write(&mp->m_super->s_umount); > >>> > >>> Are all mappings invalidated after this point? > >> > >> No; all this step does is pushes dirty filesystem [meta]data to pmem > >> before we lose DAXDEV_ALIVE... > >> > >>> The goal of the removal notification is to invalidate all DAX mappings > >>> that are no pointing to pfns that do not exist anymore, so just syncing > >>> does not seem like enough, and the shutdown is skipped above. What am I > >>> missing? > >> > >> ...however, the shutdown above only applies to filesystem metadata. In > >> effect, we avoid the fs shutdown in MF_MEM_PRE_REMOVE mode, which > >> enables the mf_dax_kill_procs calls to proceed against mapped file data. > >> I have a nagging suspicion that in non-PREREMOVE mode, we can end up > >> shutting down the filesytem on an xattr block and the 'return > >> -EFSCORRUPTED' actually prevents us from reaching all the remaining file > >> data mappings. > >> > >> IOWs, I think that clause above really ought to have returned zero so > >> that we keep the filesystem up while we're tearing down mappings, and > >> only call xfs_force_shutdown() after we've had a chance to let > >> xfs_dax_notify_ddev_failure() tear down all the mappings. > >> > >> I missed that subtlety in the initial ~30 rounds of review, but I figure > >> at this point let's just land it in 5.20 and clean up that quirk for > >> -rc1. > > > > Sure, this is a good baseline to incrementally improve. > > Hi Dan, Darrick > > Do I need to fix somewhere on this patch? I'm not sure if it is looked > good...
Eh, wait for me to send the xfs pull request and then I'll clean things up and send you a patch. :) --D > > -- > Thanks, > Ruan. > > > > >> > >>> Notice that kill_dev_dax() does unmap_mapping_range() after invalidating > >>> the dax device and that ensures that all existing mappings are gone and > >>> cannot be re-established. As far as I can see a process with an existing > >>> dax mapping will still be able to use it after this runs, no? > >> > >> I'm not sure where in akpm's tree I find kill_dev_dax()? I'm cribbing > >> off of: > >> > >> https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/tree/fs/xfs/xfs_notify_failure.c?h=mm-stable > > > > https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/tree/drivers/dax/bus.c?h=mm-stable#n381 > > > > Where the observation is that when device-dax is told that the device is > > going away it invalidates all the active mappings to that single > > character-device-inode. The hope being that in the fsdax case all the > > dax-mapped filesystem inodes would experience the same irreversible > > invalidation as the device is exiting.
