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Message-ID: <X8iaCHmmCQzzJdu3@google.com>
Date: Wed, 2 Dec 2020 23:55:52 -0800
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <yuchao0@...wei.com>
Cc: linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
Light Hsieh <Light.Hsieh@...iatek.com>
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: avoid race condition for shinker
count
On 12/03, Chao Yu wrote:
> On 2020/12/3 14:07, Jaegeuk Kim wrote:
> > On 11/11, Jaegeuk Kim wrote:
> > > Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in
> > > wrong do_shinker work. Let's avoid to get stale data by using nat_tree_lock.
> > >
> > > Reported-by: Light Hsieh <Light.Hsieh@...iatek.com>
> > > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > > ---
> > > v3:
> > > - fix to use NM_I(sbi)
> > >
> > > fs/f2fs/shrinker.c | 6 +++++-
> > > 1 file changed, 5 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
> > > index d66de5999a26..555712ba06d8 100644
> > > --- a/fs/f2fs/shrinker.c
> > > +++ b/fs/f2fs/shrinker.c
> > > @@ -18,7 +18,11 @@ static unsigned int shrinker_run_no;
> > > static unsigned long __count_nat_entries(struct f2fs_sb_info *sbi)
> > > {
> > > - long count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
> > > + long count;
> > > +
> > > + down_read(&NM_I(sbi)->nat_tree_lock);
> > > + count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
> > > + up_read(&NM_I(sbi)->nat_tree_lock);
> >
> > I just fosund this can give kernel hang due to the following backtrace.
> > f2fs_shrink_count
> > shrink_slab
> > shrink_node
> > do_try_to_free_pages
> > try_to_free_pages
> > __alloc_pages_nodemask
> > alloc_pages_current
> > allocate_slab
> > __slab_alloc
> > __slab_alloc
> > kmem_cache_alloc
> > add_free_nid
> > f2fs_flush_nat_entries
> > f2fs_write_checkpoint
>
> Oh, I missed that case.
>
> >
> > Let me just check like this.
> >
> > > From 971163330224449d90aac90957ea38f77d494f0f Mon Sep 17 00:00:00 2001
> > From: Jaegeuk Kim <jaegeuk@...nel.org>
> > Date: Fri, 6 Nov 2020 13:22:05 -0800
> > Subject: [PATCH] f2fs: avoid race condition for shrinker count
> >
> > Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in
> > wrong do_shinker work. Let's avoid to return insane overflowed value.
> >
> > Reported-by: Light Hsieh <Light.Hsieh@...iatek.com>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> > fs/f2fs/shrinker.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
> > index d66de5999a26..75b5b4aaed99 100644
> > --- a/fs/f2fs/shrinker.c
> > +++ b/fs/f2fs/shrinker.c
> > @@ -18,9 +18,9 @@ static unsigned int shrinker_run_no;
> > static unsigned long __count_nat_entries(struct f2fs_sb_info *sbi)
> > {
> > - long count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
> > -
> > - return count > 0 ? count : 0;
> > + if (NM_I(sbi)->nat_cnt > NM_I(sbi)->dirty_nat_cnt)
> > + return NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
>
> Hmm.. in the case that we are not in checkpoint progress, nat_cnt and dirty_nat_cnt
> is mutable, how can we make sure the calculation is non-negative after the check
> condition? :(
How about adding another variable to monitor it?
>From bdc5a805487f0210df7ef4e85ce5a4f0471bca72 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@...nel.org>
Date: Fri, 6 Nov 2020 13:22:05 -0800
Subject: [PATCH] f2fs: avoid race condition for shrinker count
Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in
wrong do_shinker work. Let's avoid to return insane overflowed value by adding
single tracking value.
Reported-by: Light Hsieh <Light.Hsieh@...iatek.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
fs/f2fs/checkpoint.c | 2 +-
fs/f2fs/debug.c | 11 ++++++-----
fs/f2fs/f2fs.h | 10 ++++++++--
fs/f2fs/node.c | 29 ++++++++++++++++++-----------
fs/f2fs/node.h | 4 ++--
fs/f2fs/shrinker.c | 4 +---
6 files changed, 36 insertions(+), 24 deletions(-)
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 14ba1519639e..617d0f6b0836 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1619,7 +1619,7 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
goto out;
}
- if (NM_I(sbi)->dirty_nat_cnt == 0 &&
+ if (NM_I(sbi)->nat_cnt[DIRTY_NAT] == 0 &&
SIT_I(sbi)->dirty_sentries == 0 &&
prefree_segments(sbi) == 0) {
f2fs_flush_sit_entries(sbi, cpc);
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index a8357fd4f5fa..197c914119da 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -145,8 +145,8 @@ static void update_general_status(struct f2fs_sb_info *sbi)
si->node_pages = NODE_MAPPING(sbi)->nrpages;
if (sbi->meta_inode)
si->meta_pages = META_MAPPING(sbi)->nrpages;
- si->nats = NM_I(sbi)->nat_cnt;
- si->dirty_nats = NM_I(sbi)->dirty_nat_cnt;
+ si->nats = NM_I(sbi)->nat_cnt[TOTAL_NAT];
+ si->dirty_nats = NM_I(sbi)->nat_cnt[DIRTY_NAT];
si->sits = MAIN_SEGS(sbi);
si->dirty_sits = SIT_I(sbi)->dirty_sentries;
si->free_nids = NM_I(sbi)->nid_cnt[FREE_NID];
@@ -278,9 +278,10 @@ static void update_mem_info(struct f2fs_sb_info *sbi)
si->cache_mem += (NM_I(sbi)->nid_cnt[FREE_NID] +
NM_I(sbi)->nid_cnt[PREALLOC_NID]) *
sizeof(struct free_nid);
- si->cache_mem += NM_I(sbi)->nat_cnt * sizeof(struct nat_entry);
- si->cache_mem += NM_I(sbi)->dirty_nat_cnt *
- sizeof(struct nat_entry_set);
+ si->cache_mem += NM_I(sbi)->nat_cnt[TOTAL_NAT] *
+ sizeof(struct nat_entry);
+ si->cache_mem += NM_I(sbi)->nat_cnt[DIRTY_NAT] *
+ sizeof(struct nat_entry_set);
si->cache_mem += si->inmem_pages * sizeof(struct inmem_pages);
for (i = 0; i < MAX_INO_ENTRY; i++)
si->cache_mem += sbi->im[i].ino_num * sizeof(struct ino_entry);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4417f791dbc6..78394ea91717 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -818,6 +818,13 @@ enum nid_state {
MAX_NID_STATE,
};
+enum nat_state {
+ TOTAL_NAT,
+ DIRTY_NAT,
+ RECLAIMABLE_NAT,
+ MAX_NAT_STATE,
+};
+
struct f2fs_nm_info {
block_t nat_blkaddr; /* base disk address of NAT */
nid_t max_nid; /* maximum possible node ids */
@@ -833,8 +840,7 @@ struct f2fs_nm_info {
struct rw_semaphore nat_tree_lock; /* protect nat_tree_lock */
struct list_head nat_entries; /* cached nat entry list (clean) */
spinlock_t nat_list_lock; /* protect clean nat entry list */
- unsigned int nat_cnt; /* the # of cached nat entries */
- unsigned int dirty_nat_cnt; /* total num of nat entries in set */
+ unsigned int nat_cnt[MAX_NAT_STATE]; /* the # of cached nat entries */
unsigned int nat_blocks; /* # of nat blocks */
/* free node ids management */
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 42394de6c7eb..e65d73293a3f 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -62,8 +62,8 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
sizeof(struct free_nid)) >> PAGE_SHIFT;
res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 2);
} else if (type == NAT_ENTRIES) {
- mem_size = (nm_i->nat_cnt * sizeof(struct nat_entry)) >>
- PAGE_SHIFT;
+ mem_size = (nm_i->nat_cnt[TOTAL_NAT] *
+ sizeof(struct nat_entry)) >> PAGE_SHIFT;
res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 2);
if (excess_cached_nats(sbi))
res = false;
@@ -177,7 +177,8 @@ static struct nat_entry *__init_nat_entry(struct f2fs_nm_info *nm_i,
list_add_tail(&ne->list, &nm_i->nat_entries);
spin_unlock(&nm_i->nat_list_lock);
- nm_i->nat_cnt++;
+ nm_i->nat_cnt[TOTAL_NAT]++;
+ nm_i->nat_cnt[RECLAIMABLE_NAT]++;
return ne;
}
@@ -207,7 +208,8 @@ static unsigned int __gang_lookup_nat_cache(struct f2fs_nm_info *nm_i,
static void __del_from_nat_cache(struct f2fs_nm_info *nm_i, struct nat_entry *e)
{
radix_tree_delete(&nm_i->nat_root, nat_get_nid(e));
- nm_i->nat_cnt--;
+ nm_i->nat_cnt[TOTAL_NAT]--;
+ nm_i->nat_cnt[RECLAIMABLE_NAT]--;
__free_nat_entry(e);
}
@@ -253,7 +255,8 @@ static void __set_nat_cache_dirty(struct f2fs_nm_info *nm_i,
if (get_nat_flag(ne, IS_DIRTY))
goto refresh_list;
- nm_i->dirty_nat_cnt++;
+ nm_i->nat_cnt[DIRTY_NAT]++;
+ nm_i->nat_cnt[RECLAIMABLE_NAT]--;
set_nat_flag(ne, IS_DIRTY, true);
refresh_list:
spin_lock(&nm_i->nat_list_lock);
@@ -273,7 +276,8 @@ static void __clear_nat_cache_dirty(struct f2fs_nm_info *nm_i,
set_nat_flag(ne, IS_DIRTY, false);
set->entry_cnt--;
- nm_i->dirty_nat_cnt--;
+ nm_i->nat_cnt[DIRTY_NAT]--;
+ nm_i->nat_cnt[RECLAIMABLE_NAT]++;
}
static unsigned int __gang_lookup_nat_set(struct f2fs_nm_info *nm_i,
@@ -2944,14 +2948,17 @@ int f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
LIST_HEAD(sets);
int err = 0;
- /* during unmount, let's flush nat_bits before checking dirty_nat_cnt */
+ /*
+ * during unmount, let's flush nat_bits before checking
+ * nat_cnt[DIRTY_NAT].
+ */
if (enabled_nat_bits(sbi, cpc)) {
down_write(&nm_i->nat_tree_lock);
remove_nats_in_journal(sbi);
up_write(&nm_i->nat_tree_lock);
}
- if (!nm_i->dirty_nat_cnt)
+ if (!nm_i->nat_cnt[DIRTY_NAT])
return 0;
down_write(&nm_i->nat_tree_lock);
@@ -2962,7 +2969,8 @@ int f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
* into nat entry set.
*/
if (enabled_nat_bits(sbi, cpc) ||
- !__has_cursum_space(journal, nm_i->dirty_nat_cnt, NAT_JOURNAL))
+ !__has_cursum_space(journal,
+ nm_i->nat_cnt[DIRTY_NAT], NAT_JOURNAL))
remove_nats_in_journal(sbi);
while ((found = __gang_lookup_nat_set(nm_i,
@@ -3086,7 +3094,6 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
F2FS_RESERVED_NODE_NUM;
nm_i->nid_cnt[FREE_NID] = 0;
nm_i->nid_cnt[PREALLOC_NID] = 0;
- nm_i->nat_cnt = 0;
nm_i->ram_thresh = DEF_RAM_THRESHOLD;
nm_i->ra_nid_pages = DEF_RA_NID_PAGES;
nm_i->dirty_nats_ratio = DEF_DIRTY_NAT_RATIO_THRESHOLD;
@@ -3220,7 +3227,7 @@ void f2fs_destroy_node_manager(struct f2fs_sb_info *sbi)
__del_from_nat_cache(nm_i, natvec[idx]);
}
}
- f2fs_bug_on(sbi, nm_i->nat_cnt);
+ f2fs_bug_on(sbi, nm_i->nat_cnt[TOTAL_NAT]);
/* destroy nat set cache */
nid = 0;
diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index 69e5859e993c..f84541b57acb 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -126,13 +126,13 @@ static inline void raw_nat_from_node_info(struct f2fs_nat_entry *raw_ne,
static inline bool excess_dirty_nats(struct f2fs_sb_info *sbi)
{
- return NM_I(sbi)->dirty_nat_cnt >= NM_I(sbi)->max_nid *
+ return NM_I(sbi)->nat_cnt[DIRTY_NAT] >= NM_I(sbi)->max_nid *
NM_I(sbi)->dirty_nats_ratio / 100;
}
static inline bool excess_cached_nats(struct f2fs_sb_info *sbi)
{
- return NM_I(sbi)->nat_cnt >= DEF_NAT_CACHE_THRESHOLD;
+ return NM_I(sbi)->nat_cnt[TOTAL_NAT] >= DEF_NAT_CACHE_THRESHOLD;
}
static inline bool excess_dirty_nodes(struct f2fs_sb_info *sbi)
diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
index d66de5999a26..dd3c3c7a90ec 100644
--- a/fs/f2fs/shrinker.c
+++ b/fs/f2fs/shrinker.c
@@ -18,9 +18,7 @@ static unsigned int shrinker_run_no;
static unsigned long __count_nat_entries(struct f2fs_sb_info *sbi)
{
- long count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
-
- return count > 0 ? count : 0;
+ return NM_I(sbi)->nat_cnt[RECLAIMABLE_NAT];
}
static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
--
2.29.2.454.gaff20da3a2-goog
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