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Date: Mon, 7 May 2018 14:36:10 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <yuchao0@...wei.com>
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH v4] f2fs: fix to avoid race during access gc_thread
pointer
On 05/07, Chao Yu wrote:
> Thread A Thread B Thread C
> - f2fs_remount
> - stop_gc_thread
> - f2fs_sbi_store
> - issue_discard_thread
> sbi->gc_thread = NULL;
> sbi->gc_thread->gc_wake = 1
> access sbi->gc_thread->gc_urgent
>
> Previously, we allocate memory for sbi->gc_thread based on background
> gc thread mount option, the memory can be released if we turn off
> that mount option, but still there are several places access gc_thread
> pointer without considering race condition, result in NULL point
> dereference.
>
> In order to fix this issue, introduce gc_rwsem to exclude those operations.
>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> v4:
> - use introduced sbi.gc_rwsem lock instead of sb.s_umount.
We can use this first.
>From e62e8d3ece6ee8a4aeac8ffd6161d25851f8b3f0 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@...nel.org>
Date: Mon, 7 May 2018 14:22:40 -0700
Subject: [PATCH] f2fs: introduce sbi->gc_mode to determine the policy
This is to avoid sbi->gc_thread pointer access.
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
fs/f2fs/f2fs.h | 8 ++++++++
fs/f2fs/gc.c | 28 ++++++++++++----------------
fs/f2fs/gc.h | 2 --
fs/f2fs/segment.c | 4 ++--
fs/f2fs/sysfs.c | 33 +++++++++++++++++++++++++--------
5 files changed, 47 insertions(+), 28 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 80490a7991a7..779d8b26878c 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1065,6 +1065,13 @@ enum {
MAX_TIME,
};
+enum {
+ GC_NORMAL,
+ GC_IDLE_CB,
+ GC_IDLE_GREEDY,
+ GC_URGENT,
+};
+
enum {
WHINT_MODE_OFF, /* not pass down write hints */
WHINT_MODE_USER, /* try to pass down hints given by users */
@@ -1193,6 +1200,7 @@ struct f2fs_sb_info {
struct mutex gc_mutex; /* mutex for GC */
struct f2fs_gc_kthread *gc_thread; /* GC thread */
unsigned int cur_victim_sec; /* current victim section num */
+ unsigned int gc_mode; /* current GC state */
/* threshold for gc trials on pinned files */
u64 gc_pin_file_threshold;
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 9bb2ddbbed1e..7ec8ea75dfde 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -76,7 +76,7 @@ static int gc_thread_func(void *data)
* invalidated soon after by user update or deletion.
* So, I'd like to wait some time to collect dirty segments.
*/
- if (gc_th->gc_urgent) {
+ if (sbi->gc_mode == GC_URGENT) {
wait_ms = gc_th->urgent_sleep_time;
mutex_lock(&sbi->gc_mutex);
goto do_gc;
@@ -131,8 +131,6 @@ int start_gc_thread(struct f2fs_sb_info *sbi)
gc_th->max_sleep_time = DEF_GC_THREAD_MAX_SLEEP_TIME;
gc_th->no_gc_sleep_time = DEF_GC_THREAD_NOGC_SLEEP_TIME;
- gc_th->gc_idle = 0;
- gc_th->gc_urgent = 0;
gc_th->gc_wake= 0;
sbi->gc_thread = gc_th;
@@ -158,21 +156,19 @@ void stop_gc_thread(struct f2fs_sb_info *sbi)
sbi->gc_thread = NULL;
}
-static int select_gc_type(struct f2fs_gc_kthread *gc_th, int gc_type)
+static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
{
int gc_mode = (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
- if (!gc_th)
- return gc_mode;
-
- if (gc_th->gc_idle) {
- if (gc_th->gc_idle == 1)
- gc_mode = GC_CB;
- else if (gc_th->gc_idle == 2)
- gc_mode = GC_GREEDY;
- }
- if (gc_th->gc_urgent)
+ switch (sbi->gc_mode) {
+ case GC_IDLE_CB:
+ gc_mode = GC_CB;
+ break;
+ case GC_IDLE_GREEDY:
+ case GC_URGENT:
gc_mode = GC_GREEDY;
+ break;
+ }
return gc_mode;
}
@@ -187,7 +183,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
p->max_search = dirty_i->nr_dirty[type];
p->ofs_unit = 1;
} else {
- p->gc_mode = select_gc_type(sbi->gc_thread, gc_type);
+ p->gc_mode = select_gc_type(sbi, gc_type);
p->dirty_segmap = dirty_i->dirty_segmap[DIRTY];
p->max_search = dirty_i->nr_dirty[DIRTY];
p->ofs_unit = sbi->segs_per_sec;
@@ -195,7 +191,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
/* we need to check every dirty segments in the FG_GC case */
if (gc_type != FG_GC &&
- (sbi->gc_thread && !sbi->gc_thread->gc_urgent) &&
+ (sbi->gc_mode != GC_URGENT) &&
p->max_search > sbi->max_victim_search)
p->max_search = sbi->max_victim_search;
diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index b0045d4c8d1e..c8619e408009 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -36,8 +36,6 @@ struct f2fs_gc_kthread {
unsigned int no_gc_sleep_time;
/* for changing gc mode */
- unsigned int gc_idle;
- unsigned int gc_urgent;
unsigned int gc_wake;
};
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 503a98abdb2f..5a7ed06291e0 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -177,7 +177,7 @@ bool need_SSR(struct f2fs_sb_info *sbi)
if (test_opt(sbi, LFS))
return false;
- if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
+ if (sbi->gc_mode == GC_URGENT)
return true;
return free_sections(sbi) <= (node_secs + 2 * dent_secs + imeta_secs +
@@ -1418,7 +1418,7 @@ static int issue_discard_thread(void *data)
if (dcc->discard_wake)
dcc->discard_wake = 0;
- if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
+ if (sbi->gc_mode == GC_URGENT)
init_discard_policy(&dpolicy, DPOLICY_FORCE, 1);
sb_start_intwrite(sbi->sb);
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 6d8d8f41e517..dd940d156af6 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -248,16 +248,33 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
if (!strcmp(a->attr.name, "trim_sections"))
return -EINVAL;
+ if (!strcmp(a->attr.name, "gc_urgent")) {
+ if (t >= 1) {
+ sbi->gc_mode = GC_URGENT;
+ if (sbi->gc_thread) {
+ wake_up_interruptible_all(
+ &sbi->gc_thread->gc_wait_queue_head);
+ wake_up_discard_thread(sbi, true);
+ }
+ } else {
+ sbi->gc_mode = GC_NORMAL;
+ }
+ return count;
+ }
+ if (!strcmp(a->attr.name, "gc_idle")) {
+ if (t == GC_IDLE_CB)
+ sbi->gc_mode = GC_IDLE_CB;
+ else if (t == GC_IDLE_GREEDY)
+ sbi->gc_mode = GC_IDLE_GREEDY;
+ else
+ sbi->gc_mode = GC_NORMAL;
+ return count;
+ }
+
*ui = t;
if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0)
f2fs_reset_iostat(sbi);
- if (!strcmp(a->attr.name, "gc_urgent") && t == 1 && sbi->gc_thread) {
- sbi->gc_thread->gc_wake = 1;
- wake_up_interruptible_all(&sbi->gc_thread->gc_wait_queue_head);
- wake_up_discard_thread(sbi, true);
- }
-
return count;
}
@@ -349,8 +366,8 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent_sleep_time,
F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_min_sleep_time, min_sleep_time);
F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_max_sleep_time, max_sleep_time);
F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
-F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle);
-F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_urgent, gc_urgent);
+F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_idle, gc_mode);
+F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_urgent, gc_mode);
F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
--
2.17.0.484.g0c8726318c-goog
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