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Date: Wed, 01 May 2013 13:38:16 +0900
From: Jaegeuk Kim <jaegeuk.kim@...sung.com>
To: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH v3] f2fs: use f2fs_iget_nowait again
change log from v2:
o slighly change the previous approach
From 42e49df33bacafc20434e39fc127c9722c9f8691 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk.kim@...sung.com>
Date: Tue, 30 Apr 2013 11:33:27 +0900
Subject: [PATCH] f2fs: avoid deadlock during evict after f2fs_gc
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
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@...sung.com>
---
fs/f2fs/f2fs.h | 1 +
fs/f2fs/gc.c | 1 +
fs/f2fs/super.c | 19 +++++++++++++++++++
3 files changed, 21 insertions(+)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 20aab02..beb3f06 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -846,6 +846,7 @@ enum {
FI_INC_LINK, /* need to increment i_nlink */
FI_ACL_MODE, /* indicate acl mode */
FI_NO_ALLOC, /* should not allocate any blocks */
+ FI_ON_GC, /* indicate inode is on gc */
};
static inline void set_inode_flag(struct f2fs_inode_info *fi, int flag)
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 1496159..258b786 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -345,6 +345,7 @@ repeat:
}
new_ie->inode = inode;
list_add_tail(&new_ie->list, ilist);
+ set_inode_flag(F2FS_I(inode), FI_ON_GC);
}
static void put_gc_inode(struct list_head *ilist)
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 5835aaf..6ac1f42 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -98,6 +98,24 @@ static struct inode *f2fs_alloc_inode(struct
super_block *sb)
return &fi->vfs_inode;
}
+static int f2fs_drop_inode(struct inode *inode)
+{
+ int drop = generic_drop_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->i_state & I_SYNC &&
+ is_inode_flag_set(F2FS_I(inode), FI_ON_GC))
+ drop = 0;
+ clear_inode_flag(F2FS_I(inode), FI_ON_GC);
+ return drop;
+}
+
static void f2fs_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
@@ -232,6 +250,7 @@ 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,
--
1.8.1.3.566.gaa39828
--
Jaegeuk Kim
Samsung
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