[Ocfs2-devel] [PATCH] Revert iput deferring code in ocfs2_drop_dentry_lock
Goldwyn Rodrigues
rgoldwyn at suse.de
Wed Jan 15 15:17:55 PST 2014
On 01/15/2014 09:53 AM, Jan Kara wrote:
> On Wed 15-01-14 09:32:39, Goldwyn Rodrigues wrote:
>> On 01/15/2014 07:33 AM, Jan Kara wrote:
>>> On Wed 15-01-14 06:51:51, Goldwyn Rodrigues wrote:
>>>> The following patches are reverted in this patch because these
>>>> patches caused regression in the unlink() calls.
>>>>
>>>> ea455f8ab68338ba69f5d3362b342c115bea8e13 - ocfs2: Push out dropping
>>>> of dentry lock to ocfs2_wq
>>>> f7b1aa69be138ad9d7d3f31fa56f4c9407f56b6a - ocfs2: Fix deadlock on umount
>>>> 5fd131893793567c361ae64cbeb28a2a753bbe35 - ocfs2: Don't oops in
>>>> ocfs2_kill_sb on a failed mount
>>>>
>>>> The regression is caused because these patches delay the iput() in case
>>>> of dentry unlocks. This also delays the unlocking of the open lockres.
>>>> The open lockresource is required to test if the inode can be wiped from
>>>> disk on not. When the deleting node does not get the open lock, it marks
>>>> it as orphan (even though it is not in use by another node/process)
>>>> and causes a journal checkpoint. This delays operations following the
>>>> inode eviction. This also moves the inode to the orphaned inode
>>>> which further causes more I/O and a lot of unneccessary orphans.
>>>>
>>>> As for the fix, I tried reproducing the problem by using quotas and enabling
>>>> lockdep, but the issue could not be reproduced.
>>> So I was thinking about this for a while trying to remember... What it
>>> really boils down to is whether it is OK to call ocfs2_delete_inode() from
>>> DLM downconvert thread. Bear in mind that ocfs2_delete_inode() takes all
>>> kinds of interesting cluster locks meaning that the downconvert thread can
>>> block waiting to acquire some cluster lock. That seems like asking for
>>> trouble to me (i.e., what if the node holding the lock we need from
>>> downconvert thread needs a lock from us first?) but maybe it is OK these
>>> days.
>>>
>>
>> The only lock it tries to take is the "inode lock" resource, which
>> seems to be fine to take.
> Why is it obviously fine? Some other node might be holding the inode lock
> and still write to the inode. If that needs a cluster lock for block
> allocation and that allocation cluster lock is currently hold by our node,
> we are screwed. Aren't we?
>
No. If another thread is using the allocation cluster lock implies we
already have the inode lock. Cluster locks are also taken in a strict
order in order to avoid ABBA locking.
>> It is taken to refresh the inode from
>> disk. The other cluster lock is the "open lock", which is taken in a
>> try-lock fashion and is not blocking.
>>
>> I don't see quota code using any cluster locking, but if there is
>> anything interfering, I would like to know.
> Quota code can take e.g. inode lock on the quota file during
> dquot_initialize() call. It's not common (usually the quota structure is
> already cached in memory) but it can happen.
This seems safe, because cluster lock granularity (for ocfs2) is node
level. So, if the node already holds the lock, then taking it again
would succeed and just increment the hold count.
>
> Honza
>
>>>> Signed-off-by: Srinivas Eeda <srinivas.eeda at oracle.com>
>>>> Signed-off-by: Goldwyn Rodrigues <rgoldwyn at suse.com>
>>>>
>>>> ---
>>>> diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c
>>>> index 0d3a97d..e2e05a1 100644
>>>> --- a/fs/ocfs2/dcache.c
>>>> +++ b/fs/ocfs2/dcache.c
>>>> @@ -37,7 +37,6 @@
>>>> #include "dlmglue.h"
>>>> #include "file.h"
>>>> #include "inode.h"
>>>> -#include "super.h"
>>>> #include "ocfs2_trace.h"
>>>>
>>>> void ocfs2_dentry_attach_gen(struct dentry *dentry)
>>>> @@ -346,52 +345,6 @@ out_attach:
>>>> return ret;
>>>> }
>>>>
>>>> -DEFINE_SPINLOCK(dentry_list_lock);
>>>> -
>>>> -/* We limit the number of dentry locks to drop in one go. We have
>>>> - * this limit so that we don't starve other users of ocfs2_wq. */
>>>> -#define DL_INODE_DROP_COUNT 64
>>>> -
>>>> -/* Drop inode references from dentry locks */
>>>> -static void __ocfs2_drop_dl_inodes(struct ocfs2_super *osb, int drop_count)
>>>> -{
>>>> - struct ocfs2_dentry_lock *dl;
>>>> -
>>>> - spin_lock(&dentry_list_lock);
>>>> - while (osb->dentry_lock_list && (drop_count < 0 || drop_count--)) {
>>>> - dl = osb->dentry_lock_list;
>>>> - osb->dentry_lock_list = dl->dl_next;
>>>> - spin_unlock(&dentry_list_lock);
>>>> - iput(dl->dl_inode);
>>>> - kfree(dl);
>>>> - spin_lock(&dentry_list_lock);
>>>> - }
>>>> - spin_unlock(&dentry_list_lock);
>>>> -}
>>>> -
>>>> -void ocfs2_drop_dl_inodes(struct work_struct *work)
>>>> -{
>>>> - struct ocfs2_super *osb = container_of(work, struct ocfs2_super,
>>>> - dentry_lock_work);
>>>> -
>>>> - __ocfs2_drop_dl_inodes(osb, DL_INODE_DROP_COUNT);
>>>> - /*
>>>> - * Don't queue dropping if umount is in progress. We flush the
>>>> - * list in ocfs2_dismount_volume
>>>> - */
>>>> - spin_lock(&dentry_list_lock);
>>>> - if (osb->dentry_lock_list &&
>>>> - !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
>>>> - queue_work(ocfs2_wq, &osb->dentry_lock_work);
>>>> - spin_unlock(&dentry_list_lock);
>>>> -}
>>>> -
>>>> -/* Flush the whole work queue */
>>>> -void ocfs2_drop_all_dl_inodes(struct ocfs2_super *osb)
>>>> -{
>>>> - __ocfs2_drop_dl_inodes(osb, -1);
>>>> -}
>>>> -
>>>> /*
>>>> * ocfs2_dentry_iput() and friends.
>>>> *
>>>> @@ -416,24 +369,16 @@ void ocfs2_drop_all_dl_inodes(struct ocfs2_super *osb)
>>>> static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
>>>> struct ocfs2_dentry_lock *dl)
>>>> {
>>>> + iput(dl->dl_inode);
>>>> ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
>>>> ocfs2_lock_res_free(&dl->dl_lockres);
>>>> -
>>>> - /* We leave dropping of inode reference to ocfs2_wq as that can
>>>> - * possibly lead to inode deletion which gets tricky */
>>>> - spin_lock(&dentry_list_lock);
>>>> - if (!osb->dentry_lock_list &&
>>>> - !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
>>>> - queue_work(ocfs2_wq, &osb->dentry_lock_work);
>>>> - dl->dl_next = osb->dentry_lock_list;
>>>> - osb->dentry_lock_list = dl;
>>>> - spin_unlock(&dentry_list_lock);
>>>> + kfree(dl);
>>>> }
>>>>
>>>> void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
>>>> struct ocfs2_dentry_lock *dl)
>>>> {
>>>> - int unlock;
>>>> + int unlock = 0;
>>>>
>>>> BUG_ON(dl->dl_count == 0);
>>>>
>>>> diff --git a/fs/ocfs2/dcache.h b/fs/ocfs2/dcache.h
>>>> index b79eff7..55f5889 100644
>>>> --- a/fs/ocfs2/dcache.h
>>>> +++ b/fs/ocfs2/dcache.h
>>>> @@ -29,13 +29,8 @@
>>>> extern const struct dentry_operations ocfs2_dentry_ops;
>>>>
>>>> struct ocfs2_dentry_lock {
>>>> - /* Use count of dentry lock */
>>>> unsigned int dl_count;
>>>> - union {
>>>> - /* Linked list of dentry locks to release */
>>>> - struct ocfs2_dentry_lock *dl_next;
>>>> - u64 dl_parent_blkno;
>>>> - };
>>>> + u64 dl_parent_blkno;
>>>>
>>>> /*
>>>> * The ocfs2_dentry_lock keeps an inode reference until
>>>> @@ -49,14 +44,9 @@ struct ocfs2_dentry_lock {
>>>> int ocfs2_dentry_attach_lock(struct dentry *dentry, struct inode *inode,
>>>> u64 parent_blkno);
>>>>
>>>> -extern spinlock_t dentry_list_lock;
>>>> -
>>>> void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
>>>> struct ocfs2_dentry_lock *dl);
>>>>
>>>> -void ocfs2_drop_dl_inodes(struct work_struct *work);
>>>> -void ocfs2_drop_all_dl_inodes(struct ocfs2_super *osb);
>>>> -
>>>> struct dentry *ocfs2_find_local_alias(struct inode *inode, u64 parent_blkno,
>>>> int skip_unhashed);
>>>>
>>>> diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
>>>> index 553f53c..6be4e1d 100644
>>>> --- a/fs/ocfs2/ocfs2.h
>>>> +++ b/fs/ocfs2/ocfs2.h
>>>> @@ -274,19 +274,16 @@ enum ocfs2_mount_options
>>>> OCFS2_MOUNT_HB_GLOBAL = 1 << 14, /* Global heartbeat */
>>>> };
>>>>
>>>> -#define OCFS2_OSB_SOFT_RO 0x0001
>>>> -#define OCFS2_OSB_HARD_RO 0x0002
>>>> -#define OCFS2_OSB_ERROR_FS 0x0004
>>>> -#define OCFS2_OSB_DROP_DENTRY_LOCK_IMMED 0x0008
>>>> -
>>>> -#define OCFS2_DEFAULT_ATIME_QUANTUM 60
>>>> +#define OCFS2_OSB_SOFT_RO 0x0001
>>>> +#define OCFS2_OSB_HARD_RO 0x0002
>>>> +#define OCFS2_OSB_ERROR_FS 0x0004
>>>> +#define OCFS2_DEFAULT_ATIME_QUANTUM 60
>>>>
>>>> struct ocfs2_journal;
>>>> struct ocfs2_slot_info;
>>>> struct ocfs2_recovery_map;
>>>> struct ocfs2_replay_map;
>>>> struct ocfs2_quota_recovery;
>>>> -struct ocfs2_dentry_lock;
>>>> struct ocfs2_super
>>>> {
>>>> struct task_struct *commit_task;
>>>> @@ -414,11 +411,6 @@ struct ocfs2_super
>>>> struct list_head blocked_lock_list;
>>>> unsigned long blocked_lock_count;
>>>>
>>>> - /* List of dentry locks to release. Anyone can add locks to
>>>> - * the list, ocfs2_wq processes the list */
>>>> - struct ocfs2_dentry_lock *dentry_lock_list;
>>>> - struct work_struct dentry_lock_work;
>>>> -
>>>> wait_queue_head_t osb_mount_event;
>>>>
>>>> /* Truncate log info */
>>>> @@ -579,18 +571,6 @@ static inline void ocfs2_set_osb_flag(struct ocfs2_super *osb,
>>>> spin_unlock(&osb->osb_lock);
>>>> }
>>>>
>>>> -
>>>> -static inline unsigned long ocfs2_test_osb_flag(struct ocfs2_super *osb,
>>>> - unsigned long flag)
>>>> -{
>>>> - unsigned long ret;
>>>> -
>>>> - spin_lock(&osb->osb_lock);
>>>> - ret = osb->osb_flags & flag;
>>>> - spin_unlock(&osb->osb_lock);
>>>> - return ret;
>>>> -}
>>>> -
>>>> static inline void ocfs2_set_ro_flag(struct ocfs2_super *osb,
>>>> int hard)
>>>> {
>>>> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
>>>> index 7d259ff..129b4db 100644
>>>> --- a/fs/ocfs2/super.c
>>>> +++ b/fs/ocfs2/super.c
>>>> @@ -1238,30 +1238,11 @@ static struct dentry *ocfs2_mount(struct file_system_type *fs_type,
>>>> return mount_bdev(fs_type, flags, dev_name, data, ocfs2_fill_super);
>>>> }
>>>>
>>>> -static void ocfs2_kill_sb(struct super_block *sb)
>>>> -{
>>>> - struct ocfs2_super *osb = OCFS2_SB(sb);
>>>> -
>>>> - /* Failed mount? */
>>>> - if (!osb || atomic_read(&osb->vol_state) == VOLUME_DISABLED)
>>>> - goto out;
>>>> -
>>>> - /* Prevent further queueing of inode drop events */
>>>> - spin_lock(&dentry_list_lock);
>>>> - ocfs2_set_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED);
>>>> - spin_unlock(&dentry_list_lock);
>>>> - /* Wait for work to finish and/or remove it */
>>>> - cancel_work_sync(&osb->dentry_lock_work);
>>>> -out:
>>>> - kill_block_super(sb);
>>>> -}
>>>> -
>>>> static struct file_system_type ocfs2_fs_type = {
>>>> .owner = THIS_MODULE,
>>>> .name = "ocfs2",
>>>> .mount = ocfs2_mount,
>>>> - .kill_sb = ocfs2_kill_sb,
>>>> -
>>>> + .kill_sb = kill_block_super,
>>>> .fs_flags = FS_REQUIRES_DEV|FS_RENAME_DOES_D_MOVE,
>>>> .next = NULL
>>>> };
>>>> @@ -1934,12 +1915,6 @@ static void ocfs2_dismount_volume(struct super_block *sb, int mnt_err)
>>>>
>>>> debugfs_remove(osb->osb_ctxt);
>>>>
>>>> - /*
>>>> - * Flush inode dropping work queue so that deletes are
>>>> - * performed while the filesystem is still working
>>>> - */
>>>> - ocfs2_drop_all_dl_inodes(osb);
>>>> -
>>>> /* Orphan scan should be stopped as early as possible */
>>>> ocfs2_orphan_scan_stop(osb);
>>>>
>>>> @@ -2274,9 +2249,6 @@ static int ocfs2_initialize_super(struct super_block *sb,
>>>> INIT_WORK(&journal->j_recovery_work, ocfs2_complete_recovery);
>>>> journal->j_state = OCFS2_JOURNAL_FREE;
>>>>
>>>> - INIT_WORK(&osb->dentry_lock_work, ocfs2_drop_dl_inodes);
>>>> - osb->dentry_lock_list = NULL;
>>>> -
>>>> /* get some pseudo constants for clustersize bits */
>>>> osb->s_clustersize_bits =
>>>> le32_to_cpu(di->id2.i_super.s_clustersize_bits);
>>>>
>>>> --
>>>> Goldwyn
>>
>>
>> --
>> Goldwyn
--
Goldwyn
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