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Date: Thu, 28 Sep 2017 22:28:25 +0800
From: Chao Yu <chao@...nel.org>
To: Chao Yu <yuchao0@...wei.com>, jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: order free nid allocator
Hi all,
It may trigger hungtask in ENOSPC case with fsstress, please ignore this patch
before an update.
Thanks,
On 2017/9/26 19:22, Chao Yu wrote:
> Previously, there is no restrict order among free nid allocators, if
> there are no free nids being cached in memory, previous allocator will
> try to load them by scanning NAT pages, but after that, these newly
> loaded free nids could be grabbed by later allocators, result in long
> delay of previous allocator during nid allocation.
>
> This patch tries to refactor alloc_nid flow to serialize allocators.
>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> fs/f2fs/f2fs.h | 3 ++-
> fs/f2fs/node.c | 63 ++++++++++++++++++++++++++++++++++++++++++++--------------
> 2 files changed, 50 insertions(+), 16 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 8fdae8ec0377..96366a141f68 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -721,7 +721,8 @@ struct f2fs_nm_info {
> struct list_head nid_list[MAX_NID_LIST];/* lists for free nids */
> unsigned int nid_cnt[MAX_NID_LIST]; /* the number of free node id */
> spinlock_t nid_list_lock; /* protect nid lists ops */
> - struct mutex build_lock; /* lock for build free nids */
> + struct semaphore build_lock; /* lock for build free nids */
> + atomic_t allocator; /* # of free nid allocators */
> unsigned char (*free_nid_bitmap)[NAT_ENTRY_BITMAP_SIZE];
> unsigned char *nat_block_bitmap;
> unsigned short *free_nid_count; /* free nid count of NAT block */
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index bfeaa0124670..e1bd6ff383df 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -2041,9 +2041,9 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
>
> void build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
> {
> - mutex_lock(&NM_I(sbi)->build_lock);
> + down(&NM_I(sbi)->build_lock);
> __build_free_nids(sbi, sync, mount);
> - mutex_unlock(&NM_I(sbi)->build_lock);
> + up(&NM_I(sbi)->build_lock);
> }
>
> /*
> @@ -2055,22 +2055,30 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
> {
> struct f2fs_nm_info *nm_i = NM_I(sbi);
> struct free_nid *i = NULL;
> + bool alloc_failed = false, lock_build = false, ret = false;
> +
> + spin_lock(&nm_i->nid_list_lock);
> retry:
> #ifdef CONFIG_F2FS_FAULT_INJECTION
> if (time_to_inject(sbi, FAULT_ALLOC_NID)) {
> f2fs_show_injection_info(FAULT_ALLOC_NID);
> - return false;
> + goto out;
> }
> #endif
> - spin_lock(&nm_i->nid_list_lock);
>
> - if (unlikely(nm_i->available_nids == 0)) {
> - spin_unlock(&nm_i->nid_list_lock);
> - return false;
> - }
> + if (unlikely(nm_i->available_nids == 0))
> + goto out;
>
> /* We should not use stale free nids created by build_free_nids */
> - if (nm_i->nid_cnt[FREE_NID_LIST] && !on_build_free_nids(nm_i)) {
> + if (nm_i->nid_cnt[FREE_NID_LIST] > atomic_read(&nm_i->allocator)) {
> +
> + if (!lock_build) {
> + if (!down_trylock(&nm_i->build_lock))
> + lock_build = true;
> + else
> + goto build;
> + }
> +
> f2fs_bug_on(sbi, list_empty(&nm_i->nid_list[FREE_NID_LIST]));
> i = list_first_entry(&nm_i->nid_list[FREE_NID_LIST],
> struct free_nid, list);
> @@ -2083,14 +2091,38 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
>
> update_free_nid_bitmap(sbi, *nid, false, false);
>
> - spin_unlock(&nm_i->nid_list_lock);
> - return true;
> + ret = true;
> + goto out;
> + }
> +build:
> + if (!alloc_failed) {
> + alloc_failed = true;
> + atomic_inc(&nm_i->allocator);
> }
> spin_unlock(&nm_i->nid_list_lock);
>
> + if (lock_build) {
> + lock_build = false;
> + up(&nm_i->build_lock);
> + }
> +
> /* Let's scan nat pages and its caches to get free nids */
> - build_free_nids(sbi, true, false);
> + down(&nm_i->build_lock);
> + lock_build = true;
> +
> + if (nm_i->nid_cnt[FREE_NID_LIST] < atomic_read(&nm_i->allocator))
> + __build_free_nids(sbi, true, false);
> +
> + spin_lock(&nm_i->nid_list_lock);
> goto retry;
> +
> +out:
> + if (alloc_failed)
> + atomic_dec(&nm_i->allocator);
> + spin_unlock(&nm_i->nid_list_lock);
> + if (lock_build)
> + up(&nm_i->build_lock);
> + return ret;
> }
>
> /*
> @@ -2154,7 +2186,7 @@ int try_to_free_nids(struct f2fs_sb_info *sbi, int nr_shrink)
> if (nm_i->nid_cnt[FREE_NID_LIST] <= MAX_FREE_NIDS)
> return 0;
>
> - if (!mutex_trylock(&nm_i->build_lock))
> + if (!down_trylock(&nm_i->build_lock))
> return 0;
>
> spin_lock(&nm_i->nid_list_lock);
> @@ -2169,7 +2201,7 @@ int try_to_free_nids(struct f2fs_sb_info *sbi, int nr_shrink)
> nr_shrink--;
> }
> spin_unlock(&nm_i->nid_list_lock);
> - mutex_unlock(&nm_i->build_lock);
> + up(&nm_i->build_lock);
>
> return nr - nr_shrink;
> }
> @@ -2656,7 +2688,8 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
> INIT_RADIX_TREE(&nm_i->nat_set_root, GFP_NOIO);
> INIT_LIST_HEAD(&nm_i->nat_entries);
>
> - mutex_init(&nm_i->build_lock);
> + sema_init(&nm_i->build_lock, 1);
> + atomic_set(&nm_i->allocator, 0);
> spin_lock_init(&nm_i->nid_list_lock);
> init_rwsem(&nm_i->nat_tree_lock);
>
>
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