f2fs: avoid deadlock during evict after f2fs_gc

o Deadlock case #1

Thread 1:
- writeback_sb_inodes
 - do_writepages
  - f2fs_write_data_pages
   - write_cache_pages
    - f2fs_write_data_page
     - f2fs_balance_fs
      - wait mutex_lock(gc_mutex)

Thread 2:
- f2fs_balance_fs
 - mutex_lock(gc_mutex)
 - f2fs_gc
  - f2fs_iget
   - wait iget_locked(inode->i_lock)

Thread 3:
- do_unlinkat
 - iput
  - lock(inode->i_lock)
   - evict
    - inode_wait_for_writeback

o Deadlock case #2

Thread 1:
- __writeback_single_inode
 : set I_SYNC
  - do_writepages
   - f2fs_write_data_page
    - f2fs_balance_fs
     - f2fs_gc
      - iput
       - evict
        - inode_wait_for_writeback(I_SYNC)

In order to avoid this, even though iput is called with the zero-reference
count, we need to stop the eviction procedure if the inode is on writeback.
So this patch links f2fs_drop_inode which checks the I_SYNC flag.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

3 files changed, 26 insertions, 2 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 2db9380f5dda..61b44542417c 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -577,6 +577,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 {
         struct inode *inode = mapping->host;
         struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
+        bool locked = false;
         int ret;
         long excess_nrtw = 0, desired_nrtw;
 
@@ -590,10 +591,12 @@ static int f2fs_write_data_pages(struct address_space *mapping,
                 wbc->nr_to_write = desired_nrtw;
         }
 
-        if (!S_ISDIR(inode->i_mode))
+        if (!S_ISDIR(inode->i_mode)) {
                 mutex_lock(&sbi->writepages);
+                locked = true;
+        }
         ret = write_cache_pages(mapping, wbc, __f2fs_writepage, mapping);
-        if (!S_ISDIR(inode->i_mode))
+        if (locked)
                 mutex_unlock(&sbi->writepages);
         f2fs_submit_bio(sbi, DATA, (wbc->sync_mode == WB_SYNC_ALL));
 
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 4aa26e53c935..47abc9722b17 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -72,6 +72,7 @@ out:
         unlock_new_inode(inode);
 fail:
         trace_f2fs_new_inode(inode, err);
+        make_bad_inode(inode);
         iput(inode);
         if (nid_free)
                 alloc_nid_failed(sbi, ino);
@@ -155,6 +156,7 @@ static int f2fs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 out:
         clear_nlink(inode);
         unlock_new_inode(inode);
+        make_bad_inode(inode);
         iput(inode);
         alloc_nid_failed(sbi, ino);
         return err;
@@ -190,6 +192,7 @@ static int f2fs_link(struct dentry *old_dentry, struct inode *dir,
         return 0;
 out:
         clear_inode_flag(F2FS_I(inode), FI_INC_LINK);
+        make_bad_inode(inode);
         iput(inode);
         return err;
 }
@@ -295,6 +298,7 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 out:
         clear_nlink(inode);
         unlock_new_inode(inode);
+        make_bad_inode(inode);
         iput(inode);
         alloc_nid_failed(sbi, inode->i_ino);
         return err;
@@ -335,6 +339,7 @@ out_fail:
         clear_inode_flag(F2FS_I(inode), FI_INC_LINK);
         clear_nlink(inode);
         unlock_new_inode(inode);
+        make_bad_inode(inode);
         iput(inode);
         alloc_nid_failed(sbi, inode->i_ino);
         return err;
@@ -382,6 +387,7 @@ static int f2fs_mknod(struct inode *dir, struct dentry *dentry,
 out:
         clear_nlink(inode);
         unlock_new_inode(inode);
+        make_bad_inode(inode);
         iput(inode);
         alloc_nid_failed(sbi, inode->i_ino);
         return err;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 5835aaf2fe2e..cd0e89a1ff8f 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -98,6 +98,20 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
         return &fi->vfs_inode;
 }
 
+static int f2fs_drop_inode(struct inode *inode)
+{
+        /*
+         * This is to avoid a deadlock condition like below.
+         * writeback_single_inode(inode)
+         *  - f2fs_write_data_page
+         *    - f2fs_gc -> iput -> evict
+         *       - inode_wait_for_writeback(inode)
+         */
+        if (!inode_unhashed(inode) && inode->i_state & I_SYNC)
+                return 0;
+        return generic_drop_inode(inode);
+}
+
 static void f2fs_i_callback(struct rcu_head *head)
 {
         struct inode *inode = container_of(head, struct inode, i_rcu);
@@ -232,6 +246,7 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 
 static struct super_operations f2fs_sops = {
         .alloc_inode    = f2fs_alloc_inode,
+        .drop_inode     = f2fs_drop_inode,
         .destroy_inode  = f2fs_destroy_inode,
         .write_inode    = f2fs_write_inode,
         .show_options   = f2fs_show_options,