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Commit 531ad7d5 authored by Jaegeuk Kim's avatar Jaegeuk Kim
Browse files

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: default avatarJaegeuk Kim <jaegeuk.kim@samsung.com>
parent ac5d156c

fs/f2fs/data.c

+5 −2
Original line number Diff line number Diff line
@@ -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));

fs/f2fs/namei.c

+6 −0
Original line number Diff line number Diff line
@@ -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;

fs/f2fs/super.c

+15 −0
Original line number Diff line number Diff line
@@ -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,