[PATCH v2] f2fs: use rb-tree to track pending discard commands

From: Chao Yu
Date: Fri Apr 14 2017 - 11:27:40 EST

From: Chao Yu <yuchao0@xxxxxxxxxx>

Introduce rb-tree based discard cache infrastructure to speed up lookup and
merge operation of discard entry.

Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
v2: fix to update discard cmd with correct size.
fs/f2fs/extent_cache.c | 15 ++--
fs/f2fs/f2fs.h | 48 ++++++++++-
fs/f2fs/segment.c | 223 ++++++++++++++++++++++++++++++++++++++++---------
3 files changed, 236 insertions(+), 50 deletions(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 68e649a31c7d..221ad086ee00 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -49,7 +49,7 @@ static struct rb_entry *__lookup_rb_tree_slow(struct rb_root *root,
return NULL;
}

-static struct rb_entry *__lookup_rb_tree(struct rb_root *root,
+struct rb_entry *__lookup_rb_tree(struct rb_root *root,
struct rb_entry *cached_re, unsigned int ofs)
{
struct rb_entry *re;
@@ -61,7 +61,7 @@ static struct rb_entry *__lookup_rb_tree(struct rb_root *root,
return re;
}

-static struct rb_node **__lookup_rb_tree_for_insert(struct f2fs_sb_info *sbi,
+struct rb_node **__lookup_rb_tree_for_insert(struct f2fs_sb_info *sbi,
struct rb_root *root, struct rb_node **parent,
unsigned int ofs)
{
@@ -92,13 +92,14 @@ static struct rb_node **__lookup_rb_tree_for_insert(struct f2fs_sb_info *sbi,
* in order to simpfy the insertion after.
* tree must stay unchanged between lookup and insertion.
*/
-static struct rb_entry *__lookup_rb_tree_ret(struct rb_root *root,
+struct rb_entry *__lookup_rb_tree_ret(struct rb_root *root,
struct rb_entry *cached_re,
unsigned int ofs,
struct rb_entry **prev_entry,
struct rb_entry **next_entry,
struct rb_node ***insert_p,
- struct rb_node **insert_parent)
+ struct rb_node **insert_parent,
+ bool force)
{
struct rb_node **pnode = &root->rb_node;
struct rb_node *parent = NULL, *tmp_node;
@@ -145,12 +146,12 @@ static struct rb_entry *__lookup_rb_tree_ret(struct rb_root *root,
return NULL;

lookup_neighbors:
- if (ofs == re->ofs) {
+ if (ofs == re->ofs || force) {
/* lookup prev node for merging backward later */
tmp_node = rb_prev(&re->rb_node);
*prev_entry = rb_entry_safe(tmp_node, struct rb_entry, rb_node);
}
- if (ofs == re->ofs + re->len - 1) {
+ if (ofs == re->ofs + re->len - 1 || force) {
/* lookup next node for merging frontward later */
tmp_node = rb_next(&re->rb_node);
*next_entry = rb_entry_safe(tmp_node, struct rb_entry, rb_node);
@@ -481,7 +482,7 @@ static void f2fs_update_extent_tree_range(struct inode *inode,
(struct rb_entry *)et->cached_en, fofs,
(struct rb_entry **)&prev_en,
(struct rb_entry **)&next_en,
- &insert_p, &insert_parent);
+ &insert_p, &insert_parent, false);
if (!en)
en = next_en;

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 562db8989a4e..ee7d6105a7a5 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -194,13 +194,26 @@ enum {
D_DONE,
};

+struct discard_info {
+ block_t lstart; /* logical start address */
+ block_t len; /* length */
+ block_t start; /* actual start address in dev */
+};
+
struct discard_cmd {
+ struct rb_node rb_node; /* rb node located in rb-tree */
+ union {
+ struct {
+ block_t lstart; /* logical start address */
+ block_t len; /* length */
+ block_t start; /* actual start address in dev */
+ };
+ struct discard_info di; /* discard info */
+
+ };
struct list_head list; /* command list */
struct completion wait; /* compleation */
struct block_device *bdev; /* bdev */
- block_t lstart; /* logical start address */
- block_t start; /* actual start address in dev */
- block_t len; /* length */
int state; /* state */
int error; /* bio error */
};
@@ -217,6 +230,7 @@ struct discard_cmd_control {
atomic_t issued_discard; /* # of issued discard */
atomic_t issing_discard; /* # of issing discard */
atomic_t discard_cmd_cnt; /* # of cached cmd count */
+ struct rb_root root; /* root of discard rb-tree */
};

/* for the list of fsync inodes, used only during recovery */
@@ -517,6 +531,24 @@ static inline void set_extent_info(struct extent_info *ei, unsigned int fofs,
ei->len = len;
}

+static inline bool __is_discard_mergeable(struct discard_info *back,
+ struct discard_info *front)
+{
+ return back->lstart + back->len == front->lstart;
+}
+
+static inline bool __is_discard_back_mergeable(struct discard_info *cur,
+ struct discard_info *back)
+{
+ return __is_discard_mergeable(back, cur);
+}
+
+static inline bool __is_discard_front_mergeable(struct discard_info *cur,
+ struct discard_info *front)
+{
+ return __is_discard_mergeable(cur, front);
+}
+
static inline bool __is_extent_mergeable(struct extent_info *back,
struct extent_info *front)
{
@@ -2573,6 +2605,16 @@ void f2fs_leave_shrinker(struct f2fs_sb_info *sbi);
/*
* extent_cache.c
*/
+struct rb_entry *__lookup_rb_tree(struct rb_root *root,
+ struct rb_entry *cached_re, unsigned int ofs);
+struct rb_node **__lookup_rb_tree_for_insert(struct f2fs_sb_info *sbi,
+ struct rb_root *root, struct rb_node **parent,
+ unsigned int ofs);
+struct rb_entry *__lookup_rb_tree_ret(struct rb_root *root,
+ struct rb_entry *cached_re, unsigned int ofs,
+ struct rb_entry **prev_entry, struct rb_entry **next_entry,
+ struct rb_node ***insert_p, struct rb_node **insert_parent,
+ bool force);
unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink);
bool f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext);
void f2fs_drop_extent_tree(struct inode *inode);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 58cfbe3d4dc7..44bb26086d28 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -672,7 +672,7 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
mutex_unlock(&dirty_i->seglist_lock);
}

-static void __add_discard_cmd(struct f2fs_sb_info *sbi,
+static struct discard_cmd *__create_discard_cmd(struct f2fs_sb_info *sbi,
struct block_device *bdev, block_t lstart,
block_t start, block_t len)
{
@@ -689,18 +689,46 @@ static void __add_discard_cmd(struct f2fs_sb_info *sbi,
dc->state = D_PREP;
dc->error = 0;
init_completion(&dc->wait);
-
- mutex_lock(&dcc->cmd_lock);
list_add_tail(&dc->list, pend_list);
- mutex_unlock(&dcc->cmd_lock);
-
atomic_inc(&dcc->discard_cmd_cnt);
+
+ return dc;
+}
+
+static struct discard_cmd *__attach_discard_cmd(struct f2fs_sb_info *sbi,
+ struct block_device *bdev, block_t lstart,
+ block_t start, block_t len,
+ struct rb_node *parent, struct rb_node **p)
+{
+ struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+ struct discard_cmd *dc;
+
+ dc = __create_discard_cmd(sbi, bdev, lstart, start, len);
+
+ rb_link_node(&dc->rb_node, parent, p);
+ rb_insert_color(&dc->rb_node, &dcc->root);
+
+ return dc;
}

-static void __remove_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *dc)
+static void __detach_discard_cmd(struct discard_cmd_control *dcc,
+ struct discard_cmd *dc)
{
if (dc->state == D_DONE)
- atomic_dec(&(SM_I(sbi)->dcc_info->issing_discard));
+ atomic_dec(&dcc->issing_discard);
+
+ list_del(&dc->list);
+ rb_erase(&dc->rb_node, &dcc->root);
+
+ kmem_cache_free(discard_cmd_slab, dc);
+
+ atomic_dec(&dcc->discard_cmd_cnt);
+}
+
+static void __remove_discard_cmd(struct f2fs_sb_info *sbi,
+ struct discard_cmd *dc)
+{
+ struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;

if (dc->error == -EOPNOTSUPP)
dc->error = 0;
@@ -708,9 +736,7 @@ static void __remove_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *d
if (dc->error)
f2fs_msg(sbi->sb, KERN_INFO,
"Issue discard failed, ret: %d", dc->error);
- list_del(&dc->list);
- kmem_cache_free(discard_cmd_slab, dc);
- atomic_dec(&SM_I(sbi)->dcc_info->discard_cmd_cnt);
+ __detach_discard_cmd(dcc, dc);
}

static void f2fs_submit_discard_endio(struct bio *bio)
@@ -754,62 +780,178 @@ static void __submit_discard_cmd(struct f2fs_sb_info *sbi,
}
}

-static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
- struct block_device *bdev, block_t blkstart, block_t blklen)
+static struct discard_cmd *__insert_discard_tree(struct f2fs_sb_info *sbi,
+ struct block_device *bdev, block_t lstart,
+ block_t start, block_t len,
+ struct rb_node **insert_p,
+ struct rb_node *insert_parent)
{
- block_t lblkstart = blkstart;
+ struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+ struct rb_node **p = &dcc->root.rb_node;
+ struct rb_node *parent = NULL;
+ struct discard_cmd *dc = NULL;

- trace_f2fs_issue_discard(bdev, blkstart, blklen);
+ if (insert_p && insert_parent) {
+ parent = insert_parent;
+ p = insert_p;
+ goto do_insert;
+ }

- if (sbi->s_ndevs) {
- int devi = f2fs_target_device_index(sbi, blkstart);
+ p = __lookup_rb_tree_for_insert(sbi, &dcc->root, &parent, lstart);
+do_insert:
+ dc = __attach_discard_cmd(sbi, bdev, lstart, start, len, parent, p);
+ if (!dc)
+ return NULL;

- blkstart -= FDEV(devi).start_blk;
- }
- __add_discard_cmd(sbi, bdev, lblkstart, blkstart, blklen);
- wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
- return 0;
+ return dc;
}

static void __punch_discard_cmd(struct f2fs_sb_info *sbi,
struct discard_cmd *dc, block_t blkaddr)
{
- block_t end_block = START_BLOCK(sbi, GET_SEGNO(sbi, blkaddr) + 1);
+ struct discard_info di = dc->di;
+ bool modified = false;

- if (dc->state == D_DONE || dc->lstart + dc->len <= end_block) {
+ if (dc->state == D_DONE || dc->len == 1) {
__remove_discard_cmd(sbi, dc);
return;
}

- if (blkaddr - dc->lstart < dc->lstart + dc->len - end_block) {
- dc->start += (end_block - dc->lstart);
- dc->len -= (end_block - dc->lstart);
- dc->lstart = end_block;
- } else {
+ if (blkaddr > di.lstart) {
dc->len = blkaddr - dc->lstart;
+ modified = true;
+ }
+
+ if (blkaddr < di.lstart + di.len - 1) {
+ if (modified) {
+ __insert_discard_tree(sbi, dc->bdev, blkaddr + 1,
+ di.start + blkaddr + 1 - di.lstart,
+ di.lstart + di.len - 1 - blkaddr,
+ NULL, NULL);
+ } else {
+ dc->lstart++;
+ dc->len--;
+ dc->start++;
+ }
}
}

-/* This should be covered by global mutex, &sit_i->sentry_lock */
-void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
+static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
+ struct block_device *bdev, block_t lstart,
+ block_t start, block_t len)
{
struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
- struct list_head *pend_list = &(dcc->discard_pend_list);
- struct list_head *wait_list = &(dcc->discard_wait_list);
- struct discard_cmd *dc, *tmp;
+ struct discard_cmd *prev_dc = NULL, *next_dc = NULL;
+ struct discard_cmd *dc;
+ struct discard_info di;
+ struct rb_node **insert_p = NULL, *insert_parent = NULL;
+ block_t end = lstart + len;

mutex_lock(&dcc->cmd_lock);

- list_for_each_entry_safe(dc, tmp, pend_list, list) {
- if (dc->lstart <= blkaddr && blkaddr < dc->lstart + dc->len)
- __punch_discard_cmd(sbi, dc, blkaddr);
+ dc = (struct discard_cmd *)__lookup_rb_tree_ret(&dcc->root,
+ NULL, lstart,
+ (struct rb_entry **)&prev_dc,
+ (struct rb_entry **)&next_dc,
+ &insert_p, &insert_parent, true);
+ if (dc)
+ prev_dc = dc;
+
+ if (!prev_dc) {
+ di.lstart = lstart;
+ di.len = next_dc ? next_dc->lstart - lstart : len;
+ di.len = min(di.len, len);
+ di.start = start;
}

- list_for_each_entry_safe(dc, tmp, wait_list, list) {
- if (dc->lstart <= blkaddr && blkaddr < dc->lstart + dc->len) {
- wait_for_completion_io(&dc->wait);
- __punch_discard_cmd(sbi, dc, blkaddr);
+ while (1) {
+ struct rb_node *node;
+ bool merged = false;
+ struct discard_cmd *tdc = NULL;
+
+ if (prev_dc) {
+ di.lstart = prev_dc->lstart + prev_dc->len;
+ if (di.lstart < lstart)
+ di.lstart = lstart;
+ if (di.lstart >= end)
+ break;
+
+ if (!next_dc || next_dc->lstart > end)
+ di.len = end - di.lstart;
+ else
+ di.len = next_dc->lstart - di.lstart;
+ di.start = start + di.lstart - lstart;
+ }
+
+ if (!di.len)
+ goto next;
+
+ if (prev_dc && prev_dc->state == D_PREP &&
+ prev_dc->bdev == bdev &&
+ __is_discard_back_mergeable(&di, &prev_dc->di)) {
+ prev_dc->di.len += di.len;
+ di = prev_dc->di;
+ tdc = prev_dc;
+ merged = true;
+ }
+
+ if (next_dc && next_dc->state == D_PREP &&
+ next_dc->bdev == bdev &&
+ __is_discard_front_mergeable(&di, &next_dc->di)) {
+ next_dc->di.lstart = di.lstart;
+ next_dc->di.len += di.len;
+ next_dc->di.start = di.start;
+ if (tdc)
+ __remove_discard_cmd(sbi, tdc);
+
+ merged = true;
}
+
+ if (!merged)
+ __insert_discard_tree(sbi, bdev, di.lstart, di.start,
+ di.len, NULL, NULL);
+ next:
+ prev_dc = next_dc;
+ if (!prev_dc)
+ break;
+
+ node = rb_next(&prev_dc->rb_node);
+ next_dc = rb_entry_safe(node, struct discard_cmd, rb_node);
+ }
+
+ mutex_unlock(&dcc->cmd_lock);
+}
+
+static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
+ struct block_device *bdev, block_t blkstart, block_t blklen)
+{
+ block_t lblkstart = blkstart;
+
+ trace_f2fs_issue_discard(bdev, blkstart, blklen);
+
+ if (sbi->s_ndevs) {
+ int devi = f2fs_target_device_index(sbi, blkstart);
+
+ blkstart -= FDEV(devi).start_blk;
+ }
+ __update_discard_tree_range(sbi, bdev, lblkstart, blkstart, blklen);
+ wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
+ return 0;
+}
+
+/* This should be covered by global mutex, &sit_i->sentry_lock */
+void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
+{
+ struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+ struct discard_cmd *dc;
+
+ mutex_lock(&dcc->cmd_lock);
+
+ dc = (struct discard_cmd *)__lookup_rb_tree(&dcc->root, NULL, blkaddr);
+ if (dc) {
+ if (dc->state != D_PREP)
+ wait_for_completion_io(&dc->wait);
+ __punch_discard_cmd(sbi, dc, blkaddr);
}

mutex_unlock(&dcc->cmd_lock);
@@ -1178,6 +1320,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
atomic_set(&dcc->discard_cmd_cnt, 0);
dcc->nr_discards = 0;
dcc->max_discards = 0;
+ dcc->root = RB_ROOT;

init_waitqueue_head(&dcc->discard_wait_queue);
SM_I(sbi)->dcc_info = dcc;
--
2.12.2.575.gb14f27f