[PATCH v2 1/2] f2fs: extract do_migrate_one_data_block() helper for GC migration

[Daejun Park]

Pull gc_data_segment()'s per-block migration body out into a static
helper.  The lock acquisition, move_data_{page,block}() dispatch,
i_gc_rwsem release and stat_inc_data_blk_count() call are now shared
through a single point so future migration paths (e.g. inode-local
packing) can reuse them instead of duplicating the sequence.

While here, change add_gc_inode() to return the inserted (or already
present) inode_entry pointer.  The caller still discards it for now;
upcoming work needs the pointer to attach per-inode state to the
entry without an extra radix-tree lookup.

No behavioral change.

Signed-off-by: Daejun Park <daejun7.park@xxxxxxxxxxx>
---
 fs/f2fs/gc.c | 109 ++++++++++++++++++++++++++++++---------------------
 1 file changed, 64 insertions(+), 45 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 69e0a8672..e232dff72 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -991,13 +991,15 @@ static struct inode *find_gc_inode(struct gc_inode_list *gc_list, nid_t ino)
 	return NULL;
 }
 
-static void add_gc_inode(struct gc_inode_list *gc_list, struct inode *inode)
+static struct inode_entry *add_gc_inode(struct gc_inode_list *gc_list,
+					struct inode *inode)
 {
 	struct inode_entry *new_ie;
 
-	if (inode == find_gc_inode(gc_list, inode->i_ino)) {
+	new_ie = radix_tree_lookup(&gc_list->iroot, inode->i_ino);
+	if (new_ie && new_ie->inode == inode) {
 		iput(inode);
-		return;
+		return new_ie;
 	}
 	new_ie = f2fs_kmem_cache_alloc(f2fs_inode_entry_slab,
 					GFP_NOFS, true, NULL);
@@ -1005,6 +1007,7 @@ static void add_gc_inode(struct gc_inode_list *gc_list, struct inode *inode)
 
 	f2fs_radix_tree_insert(&gc_list->iroot, inode->i_ino, new_ie);
 	list_add_tail(&new_ie->list, &gc_list->ilist);
+	return new_ie;
 }
 
 static void put_gc_inode(struct gc_inode_list *gc_list)
@@ -1579,6 +1582,61 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
 	return err;
 }
 
+/*
+ * do_migrate_one_data_block - migrate one valid data block at @segno+@off,
+ * identified by (@nofs, @ofs_in_node) on @inode, into the destination
+ * curseg via move_data_{page,block}().
+ *
+ * Takes i_gc_rwsem for regular files; on rwsem contention the block is
+ * skipped and sbi->skipped_gc_rwsem is incremented.  Returns the number
+ * of blocks submitted for write (0 or 1).
+ */
+static int do_migrate_one_data_block(struct f2fs_sb_info *sbi,
+				     struct inode *inode,
+				     unsigned int segno, int off,
+				     unsigned int nofs,
+				     unsigned int ofs_in_node, int gc_type)
+{
+	struct f2fs_inode_info *fi = F2FS_I(inode);
+	bool locked = false;
+	block_t start_bidx;
+	int err;
+	int submitted = 0;
+
+	if (S_ISREG(inode->i_mode)) {
+		if (!f2fs_down_write_trylock(&fi->i_gc_rwsem[WRITE])) {
+			sbi->skipped_gc_rwsem++;
+			return 0;
+		}
+		if (!f2fs_down_write_trylock(&fi->i_gc_rwsem[READ])) {
+			sbi->skipped_gc_rwsem++;
+			f2fs_up_write(&fi->i_gc_rwsem[WRITE]);
+			return 0;
+		}
+		locked = true;
+
+		/* wait for all inflight aio data */
+		inode_dio_wait(inode);
+	}
+
+	start_bidx = f2fs_start_bidx_of_node(nofs, inode) + ofs_in_node;
+	if (f2fs_meta_inode_gc_required(inode))
+		err = move_data_block(inode, start_bidx, gc_type, segno, off);
+	else
+		err = move_data_page(inode, start_bidx, gc_type, segno, off);
+
+	if (!err && (gc_type == FG_GC || f2fs_meta_inode_gc_required(inode)))
+		submitted = 1;
+
+	if (locked) {
+		f2fs_up_write(&fi->i_gc_rwsem[READ]);
+		f2fs_up_write(&fi->i_gc_rwsem[WRITE]);
+	}
+
+	stat_inc_data_blk_count(sbi, 1, gc_type);
+	return submitted;
+}
+
 /*
  * This function tries to get parent node of victim data block, and identifies
  * data block validity. If the block is valid, copy that with cold status and
@@ -1712,48 +1770,9 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 
 		/* phase 4 */
 		inode = find_gc_inode(gc_list, dni.ino);
-		if (inode) {
-			struct f2fs_inode_info *fi = F2FS_I(inode);
-			bool locked = false;
-			int err;
-
-			if (S_ISREG(inode->i_mode)) {
-				if (!f2fs_down_write_trylock(&fi->i_gc_rwsem[WRITE])) {
-					sbi->skipped_gc_rwsem++;
-					continue;
-				}
-				if (!f2fs_down_write_trylock(
-						&fi->i_gc_rwsem[READ])) {
-					sbi->skipped_gc_rwsem++;
-					f2fs_up_write(&fi->i_gc_rwsem[WRITE]);
-					continue;
-				}
-				locked = true;
-
-				/* wait for all inflight aio data */
-				inode_dio_wait(inode);
-			}
-
-			start_bidx = f2fs_start_bidx_of_node(nofs, inode)
-								+ ofs_in_node;
-			if (f2fs_meta_inode_gc_required(inode))
-				err = move_data_block(inode, start_bidx,
-							gc_type, segno, off);
-			else
-				err = move_data_page(inode, start_bidx, gc_type,
-								segno, off);
-
-			if (!err && (gc_type == FG_GC ||
-					f2fs_meta_inode_gc_required(inode)))
-				submitted++;
-
-			if (locked) {
-				f2fs_up_write(&fi->i_gc_rwsem[READ]);
-				f2fs_up_write(&fi->i_gc_rwsem[WRITE]);
-			}
-
-			stat_inc_data_blk_count(sbi, 1, gc_type);
-		}
+		if (inode)
+			submitted += do_migrate_one_data_block(sbi, inode,
+					segno, off, nofs, ofs_in_node, gc_type);
 	}
 
 	if (++phase < 5) {
-- 
2.43.0