f2fs: ioctl for removing a range from F2FS

This ioctl shrinks a given length (aligned to sections) from end of the
main area. Any cursegs and valid blocks will be moved out before
invalidating the range.

This feature can be used for adjusting partition sizes online.

History of the patch:

Sahitya Tummala:
 - Add this ioctl for f2fs_compat_ioctl() as well.
 - Fix debugfs status to reflect the online resize changes.
 - Fix potential race between online resize path and allocate new data
   block path or gc path.

Others:
 - Rename some identifiers.
 - Add some error handling branches.
 - Clear sbi->next_victim_seg[BG_GC/FG_GC] in shrinking range.
 - Implement this interface as ext4's, and change the parameter from shrunk
bytes to new block count of F2FS.
 - During resizing, force to empty sit_journal and forbid adding new
   entries to it, in order to avoid invalid segno in journal after resize.
 - Reduce sbi->user_block_count before resize starts.
 - Commit the updated superblock first, and then update in-memory metadata
   only when the former succeeds.
 - Target block count must align to sections.
 - Write checkpoint before and after committing the new superblock, w/o
CP_FSCK_FLAG respectively, so that the FS can be fixed by fsck even if
resize fails after the new superblock is committed.
 - In free_segment_range(), reduce granularity of gc_mutex.
 - Add protection on curseg migration.
 - Add freeze_bdev() and thaw_bdev() for resize fs.
 - Remove CUR_MAIN_SECS and use MAIN_SECS directly for allocation.
 - Recover super_block and FS metadata when resize fails.
 - No need to clear CP_FSCK_FLAG in update_ckpt_flags().
 - Clean up the sb and fs metadata update functions for resize_fs.

Geert Uytterhoeven:
 - Use div_u64*() for 64-bit divisions

Arnd Bergmann:
 - Not all architectures support get_user() with a 64-bit argument:
    ERROR: "__get_user_bad" [fs/f2fs/f2fs.ko] undefined!
    Use copy_from_user() here, this will always work.

Signed-off-by: Qiuyang Sun <sunqiuyang@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 37 insertions, 2 deletions

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 54a3e398d1ea..198b2e68a487 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2657,6 +2657,40 @@ static void allocate_segment_by_default(struct f2fs_sb_info *sbi,
 	stat_inc_seg_type(sbi, curseg);
 }
 
+void allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
+					unsigned int start, unsigned int end)
+{
+	struct curseg_info *curseg = CURSEG_I(sbi, type);
+	unsigned int segno;
+
+	down_read(&SM_I(sbi)->curseg_lock);
+	mutex_lock(&curseg->curseg_mutex);
+	down_write(&SIT_I(sbi)->sentry_lock);
+
+	segno = CURSEG_I(sbi, type)->segno;
+	if (segno < start || segno > end)
+		goto unlock;
+
+	if (f2fs_need_SSR(sbi) && get_ssr_segment(sbi, type))
+		change_curseg(sbi, type);
+	else
+		new_curseg(sbi, type, true);
+
+	stat_inc_seg_type(sbi, curseg);
+
+	locate_dirty_segment(sbi, segno);
+unlock:
+	up_write(&SIT_I(sbi)->sentry_lock);
+
+	if (segno != curseg->segno)
+		f2fs_msg(sbi->sb, KERN_NOTICE,
+			"For resize: curseg of type %d: %u ==> %u",
+			type, segno, curseg->segno);
+
+	mutex_unlock(&curseg->curseg_mutex);
+	up_read(&SM_I(sbi)->curseg_lock);
+}
+
 void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi)
 {
 	struct curseg_info *curseg;
@@ -3786,7 +3820,7 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	struct f2fs_journal *journal = curseg->journal;
 	struct sit_entry_set *ses, *tmp;
 	struct list_head *head = &SM_I(sbi)->sit_entry_set;
-	bool to_journal = true;
+	bool to_journal = !is_sbi_flag_set(sbi, SBI_IS_RESIZEFS);
 	struct seg_entry *se;
 
 	down_write(&sit_i->sentry_lock);
@@ -3805,7 +3839,8 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	 * entries, remove all entries from journal and add and account
 	 * them in sit entry set.
 	 */
-	if (!__has_cursum_space(journal, sit_i->dirty_sentries, SIT_JOURNAL))
+	if (!__has_cursum_space(journal, sit_i->dirty_sentries, SIT_JOURNAL) ||
+								!to_journal)
 		remove_sits_in_journal(sbi);
 
 	/*