Re: [f2fs-dev] [PATCH] f2fs: prevent meta updates while checkpoint is in progress

From: Jaegeuk Kim
Date: Thu Apr 16 2020 - 17:40:48 EST

On 04/14, Jaegeuk Kim wrote:
> On 04/13, Jaegeuk Kim wrote:
> > On 04/03, Jaegeuk Kim wrote:
> > > On 04/03, Jaegeuk Kim wrote:
> > > > On 04/01, Sahitya Tummala wrote:
> > > > > Hi Jaegeuk,
> > > > >
> > > > > Got it.
> > > > > The diff below looks good to me.
> > > > > Would you like me to test it and put a patch for this?
> > > >
> > > > Sahitya, Chao,
> > > >
> > > > Could you please take a look at this patch and test intensively?
> > > >
> > > > Thanks,

v5:
- add signal handler

Sahitya raised an issue:
- prevent meta updates while checkpoint is in progress

allocate_segment_for_resize() can cause metapage updates if
it requires to change the current node/data segments for resizing.
Stop these meta updates when there is a checkpoint already
in progress to prevent inconsistent CP data.

Signed-off-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
fs/f2fs/checkpoint.c | 6 +-
fs/f2fs/f2fs.h | 2 +-
fs/f2fs/file.c | 5 +-
fs/f2fs/gc.c | 114 ++++++++++++++++++++----------------
fs/f2fs/super.c | 1 -
include/trace/events/f2fs.h | 4 +-
6 files changed, 74 insertions(+), 58 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 6be357c8e0020..dcb3a15574c99 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1554,7 +1554,8 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
return 0;
f2fs_warn(sbi, "Start checkpoint disabled!");
}
- mutex_lock(&sbi->cp_mutex);
+ if (cpc->reason != CP_RESIZE)
+ mutex_lock(&sbi->cp_mutex);

if (!is_sbi_flag_set(sbi, SBI_IS_DIRTY) &&
((cpc->reason & CP_FASTBOOT) || (cpc->reason & CP_SYNC) ||
@@ -1623,7 +1624,8 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
f2fs_update_time(sbi, CP_TIME);
trace_f2fs_write_checkpoint(sbi->sb, cpc->reason, "finish checkpoint");
out:
- mutex_unlock(&sbi->cp_mutex);
+ if (cpc->reason != CP_RESIZE)
+ mutex_unlock(&sbi->cp_mutex);
return err;
}

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index dd9c1de7c59d2..9dd1fc957b943 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -194,6 +194,7 @@ enum {
#define CP_DISCARD 0x00000010
#define CP_TRIMMED 0x00000020
#define CP_PAUSE 0x00000040
+#define CP_RESIZE 0x00000080

#define MAX_DISCARD_BLOCKS(sbi) BLKS_PER_SEC(sbi)
#define DEF_MAX_DISCARD_REQUEST 8 /* issue 8 discards per round */
@@ -1423,7 +1424,6 @@ struct f2fs_sb_info {
unsigned int segs_per_sec; /* segments per section */
unsigned int secs_per_zone; /* sections per zone */
unsigned int total_sections; /* total section count */
- struct mutex resize_mutex; /* for resize exclusion */
unsigned int total_node_count; /* total node block count */
unsigned int total_valid_node_count; /* valid node block count */
loff_t max_file_blocks; /* max block index of file */
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index dc470358f25eb..212c5996d3807 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3306,7 +3306,6 @@ static int f2fs_ioc_resize_fs(struct file *filp, unsigned long arg)
{
struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(filp));
__u64 block_count;
- int ret;

if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -3318,9 +3317,7 @@ static int f2fs_ioc_resize_fs(struct file *filp, unsigned long arg)
sizeof(block_count)))
return -EFAULT;

- ret = f2fs_resize_fs(sbi, block_count);
-
- return ret;
+ return f2fs_resize_fs(sbi, block_count);
}

static int f2fs_ioc_enable_verity(struct file *filp, unsigned long arg)
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 26248c8936db0..c979dd1add5de 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1399,12 +1399,29 @@ void f2fs_build_gc_manager(struct f2fs_sb_info *sbi)
GET_SEGNO(sbi, FDEV(0).end_blk) + 1;
}

-static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
- unsigned int end)
+static int free_segment_range(struct f2fs_sb_info *sbi,
+ unsigned int secs, bool gc_only)
{
- int type;
- unsigned int segno, next_inuse;
+ unsigned int segno, next_inuse, start, end;
+ struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
+ int gc_mode, gc_type;
int err = 0;
+ int type;
+
+ /* Force block allocation for GC */
+ MAIN_SECS(sbi) -= secs;
+ start = MAIN_SECS(sbi) * sbi->segs_per_sec;
+ end = MAIN_SEGS(sbi) - 1;
+
+ mutex_lock(&DIRTY_I(sbi)->seglist_lock);
+ for (gc_mode = 0; gc_mode < MAX_GC_POLICY; gc_mode++)
+ if (SIT_I(sbi)->last_victim[gc_mode] >= start)
+ SIT_I(sbi)->last_victim[gc_mode] = 0;
+
+ for (gc_type = BG_GC; gc_type <= FG_GC; gc_type++)
+ if (sbi->next_victim_seg[gc_type] >= start)
+ sbi->next_victim_seg[gc_type] = NULL_SEGNO;
+ mutex_unlock(&DIRTY_I(sbi)->seglist_lock);

/* Move out cursegs from the target range */
for (type = CURSEG_HOT_DATA; type < NR_CURSEG_TYPE; type++)
@@ -1417,18 +1434,22 @@ static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
.iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
};

- down_write(&sbi->gc_lock);
do_garbage_collect(sbi, segno, &gc_list, FG_GC);
- up_write(&sbi->gc_lock);
put_gc_inode(&gc_list);

- if (get_valid_blocks(sbi, segno, true))
- return -EAGAIN;
+ if (!gc_only && get_valid_blocks(sbi, segno, true)) {
+ err = -EAGAIN;
+ goto out;
+ }
+ if (fatal_signal_pending(current))
+ return -ERESTARTSYS;
}
+ if (gc_only)
+ goto out;

- err = f2fs_sync_fs(sbi->sb, 1);
+ err = f2fs_write_checkpoint(sbi, &cpc);
if (err)
- return err;
+ goto out;

next_inuse = find_next_inuse(FREE_I(sbi), end + 1, start);
if (next_inuse <= end) {
@@ -1436,6 +1457,8 @@ static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
next_inuse);
f2fs_bug_on(sbi, 1);
}
+out:
+ MAIN_SECS(sbi) -= secs;
return err;
}

@@ -1481,6 +1504,7 @@ static void update_fs_metadata(struct f2fs_sb_info *sbi, int secs)

SM_I(sbi)->segment_count = (int)SM_I(sbi)->segment_count + segs;
MAIN_SEGS(sbi) = (int)MAIN_SEGS(sbi) + segs;
+ MAIN_SECS(sbi) += secs;
FREE_I(sbi)->free_sections = (int)FREE_I(sbi)->free_sections + secs;
FREE_I(sbi)->free_segments = (int)FREE_I(sbi)->free_segments + segs;
F2FS_CKPT(sbi)->user_block_count = cpu_to_le64(user_block_count + blks);
@@ -1502,8 +1526,8 @@ static void update_fs_metadata(struct f2fs_sb_info *sbi, int secs)
int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
{
__u64 old_block_count, shrunk_blocks;
+ struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
unsigned int secs;
- int gc_mode, gc_type;
int err = 0;
__u32 rem;

@@ -1538,10 +1562,27 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
return -EINVAL;
}

- freeze_bdev(sbi->sb->s_bdev);
-
shrunk_blocks = old_block_count - block_count;
secs = div_u64(shrunk_blocks, BLKS_PER_SEC(sbi));
+
+ /* stop other GC */
+ if (!down_write_trylock(&sbi->gc_lock))
+ return -EAGAIN;
+
+ /* stop CP to protect MAIN_SEC in free_segment_range */
+ f2fs_lock_op(sbi);
+ err = free_segment_range(sbi, secs, true);
+ f2fs_unlock_op(sbi);
+ up_write(&sbi->gc_lock);
+ if (err)
+ return err;
+
+ set_sbi_flag(sbi, SBI_IS_RESIZEFS);
+
+ freeze_super(sbi->sb);
+ down_write(&sbi->gc_lock);
+ mutex_lock(&sbi->cp_mutex);
+
spin_lock(&sbi->stat_lock);
if (shrunk_blocks + valid_user_blocks(sbi) +
sbi->current_reserved_blocks + sbi->unusable_block_count +
@@ -1550,69 +1591,44 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
else
sbi->user_block_count -= shrunk_blocks;
spin_unlock(&sbi->stat_lock);
- if (err) {
- thaw_bdev(sbi->sb->s_bdev, sbi->sb);
- return err;
- }
-
- mutex_lock(&sbi->resize_mutex);
- set_sbi_flag(sbi, SBI_IS_RESIZEFS);
-
- mutex_lock(&DIRTY_I(sbi)->seglist_lock);
-
- MAIN_SECS(sbi) -= secs;
-
- for (gc_mode = 0; gc_mode < MAX_GC_POLICY; gc_mode++)
- if (SIT_I(sbi)->last_victim[gc_mode] >=
- MAIN_SECS(sbi) * sbi->segs_per_sec)
- SIT_I(sbi)->last_victim[gc_mode] = 0;
-
- for (gc_type = BG_GC; gc_type <= FG_GC; gc_type++)
- if (sbi->next_victim_seg[gc_type] >=
- MAIN_SECS(sbi) * sbi->segs_per_sec)
- sbi->next_victim_seg[gc_type] = NULL_SEGNO;
-
- mutex_unlock(&DIRTY_I(sbi)->seglist_lock);
+ if (err)
+ goto out_err;

- err = free_segment_range(sbi, MAIN_SECS(sbi) * sbi->segs_per_sec,
- MAIN_SEGS(sbi) - 1);
+ err = free_segment_range(sbi, secs, false);
if (err)
- goto out;
+ goto recover_out;

update_sb_metadata(sbi, -secs);

err = f2fs_commit_super(sbi, false);
if (err) {
update_sb_metadata(sbi, secs);
- goto out;
+ goto recover_out;
}

- mutex_lock(&sbi->cp_mutex);
update_fs_metadata(sbi, -secs);
clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
set_sbi_flag(sbi, SBI_IS_DIRTY);
- mutex_unlock(&sbi->cp_mutex);

- err = f2fs_sync_fs(sbi->sb, 1);
+ err = f2fs_write_checkpoint(sbi, &cpc);
if (err) {
- mutex_lock(&sbi->cp_mutex);
update_fs_metadata(sbi, secs);
- mutex_unlock(&sbi->cp_mutex);
update_sb_metadata(sbi, secs);
f2fs_commit_super(sbi, false);
}
-out:
+recover_out:
if (err) {
set_sbi_flag(sbi, SBI_NEED_FSCK);
f2fs_err(sbi, "resize_fs failed, should run fsck to repair!");

- MAIN_SECS(sbi) += secs;
spin_lock(&sbi->stat_lock);
sbi->user_block_count += shrunk_blocks;
spin_unlock(&sbi->stat_lock);
}
+out_err:
+ mutex_unlock(&sbi->cp_mutex);
+ up_write(&sbi->gc_lock);
+ thaw_super(sbi->sb);
clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
- mutex_unlock(&sbi->resize_mutex);
- thaw_bdev(sbi->sb->s_bdev, sbi->sb);
return err;
}
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index e3a323ff04c34..ad3b66c3dbe0e 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3420,7 +3420,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
init_rwsem(&sbi->gc_lock);
mutex_init(&sbi->writepages);
mutex_init(&sbi->cp_mutex);
- mutex_init(&sbi->resize_mutex);
init_rwsem(&sbi->node_write);
init_rwsem(&sbi->node_change);

diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
index 3577fa67690af..421a661bfd5aa 100644
--- a/include/trace/events/f2fs.h
+++ b/include/trace/events/f2fs.h
@@ -50,6 +50,7 @@ TRACE_DEFINE_ENUM(CP_RECOVERY);
TRACE_DEFINE_ENUM(CP_DISCARD);
TRACE_DEFINE_ENUM(CP_TRIMMED);
TRACE_DEFINE_ENUM(CP_PAUSE);
+TRACE_DEFINE_ENUM(CP_RESIZE);

#define show_block_type(type) \
__print_symbolic(type, \
@@ -126,7 +127,8 @@ TRACE_DEFINE_ENUM(CP_PAUSE);
{ CP_RECOVERY, "Recovery" }, \
{ CP_DISCARD, "Discard" }, \
{ CP_PAUSE, "Pause" }, \
- { CP_TRIMMED, "Trimmed" })
+ { CP_TRIMMED, "Trimmed" }, \
+ { CP_RESIZE, "Resize" })

#define show_fsync_cpreason(type) \
__print_symbolic(type, \
--
2.26.1.301.g55bc3eb7cb9-goog