Messages in this thread | | | Date | Thu, 18 Aug 2022 19:19:28 +0800 | Subject | Re: [RFC PATCH v6] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind | From | Shiyang Ruan <> |
| |
在 2022/8/3 12:33, Darrick J. Wong 写道: > On Wed, Aug 03, 2022 at 02:43:20AM +0000, ruansy.fnst@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.fnst@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.stgit@dwillia2-desk3.amr.corp.intel.com/ >>>>>> >>>>>> Signed-off-by: Shiyang Ruan <ruansy.fnst@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. :)
Hi, Darrick
How is your patch going on? Forgive me for being so annoying. I'm afraid of missing your patch, so I'm asking for confirmation.
-- Thanks, Ruan.
> > --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.
| |