f2fs: avoid race condition in handling wait_io

__submit_merged_bio    f2fs_write_end_io        f2fs_write_end_io
                       wait_io = X              wait_io = x
                       complete(X)              complete(X)
                       wait_io = NULL
wait_for_completion()
free(X)
                                                 spin_lock(X)
                                                 kernel panic

In order to avoid this, this patch removes the wait_io facility.
Instead, we can use wait_on_all_pages_writeback(sbi) to wait for end_ios.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

3 files changed, 10 insertions, 29 deletions

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index ca514d599b79..dd6a357a59de 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -978,6 +978,9 @@ static void do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
         /* Here, we only have one bio having CP pack */
         sync_meta_pages(sbi, META_FLUSH, LONG_MAX);
 
+        /* wait for previous submitted meta pages writeback */
+        wait_on_all_pages_writeback(sbi);
+
         release_dirty_inode(sbi);
 
         if (unlikely(f2fs_cp_error(sbi)))
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index ceee1a69c5aa..8f164432408e 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -61,11 +61,6 @@ static void f2fs_write_end_io(struct bio *bio, int err)
                 dec_page_count(sbi, F2FS_WRITEBACK);
         }
 
-        if (sbi->wait_io) {
-                complete(sbi->wait_io);
-                sbi->wait_io = NULL;
-        }
-
         if (!get_pages(sbi, F2FS_WRITEBACK) &&
                         !list_empty(&sbi->cp_wait.task_list))
                 wake_up(&sbi->cp_wait);
@@ -95,34 +90,18 @@ static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr,
 static void __submit_merged_bio(struct f2fs_bio_info *io)
 {
         struct f2fs_io_info *fio = &io->fio;
-        int rw;
 
         if (!io->bio)
                 return;
 
-        rw = fio->rw;
-
-        if (is_read_io(rw)) {
-                trace_f2fs_submit_read_bio(io->sbi->sb, rw,
-                                                fio->type, io->bio);
-                submit_bio(rw, io->bio);
-        } else {
-                trace_f2fs_submit_write_bio(io->sbi->sb, rw,
-                                                fio->type, io->bio);
-                /*
-                 * META_FLUSH is only from the checkpoint procedure, and we
-                 * should wait this metadata bio for FS consistency.
-                 */
-                if (fio->type == META_FLUSH) {
-                        DECLARE_COMPLETION_ONSTACK(wait);
-                        io->sbi->wait_io = &wait;
-                        submit_bio(rw, io->bio);
-                        wait_for_completion(&wait);
-                } else {
-                        submit_bio(rw, io->bio);
-                }
-        }
+        if (is_read_io(fio->rw))
+                trace_f2fs_submit_read_bio(io->sbi->sb, fio->rw,
+                                                        fio->type, io->bio);
+        else
+                trace_f2fs_submit_write_bio(io->sbi->sb, fio->rw,
+                                                        fio->type, io->bio);
 
+        submit_bio(fio->rw, io->bio);
         io->bio = NULL;
 }
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index afe3022ffac5..5a9705842f10 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -516,7 +516,6 @@ struct f2fs_sb_info {
         /* for bio operations */
         struct f2fs_bio_info read_io;                   /* for read bios */
         struct f2fs_bio_info write_io[NR_PAGE_TYPE];    /* for write bios */
-        struct completion *wait_io;             /* for completion bios */
 
         /* for checkpoint */
         struct f2fs_checkpoint *ckpt;           /* raw checkpoint pointer */