ext4: add lockdep annotations for i_data_sem

[ Upstream commit daf647d2dd58cec59570d7698a45b98e580f2076 ]

With the internal Quota feature, mke2fs creates empty quota inodes and
quota usage tracking is enabled as soon as the file system is mounted.
Since quotacheck is no longer preallocating all of the blocks in the
quota inode that are likely needed to be written to, we are now seeing
a lockdep false positive caused by needing to allocate a quota block
from inside ext4_map_blocks(), while holding i_data_sem for a data
inode.  This results in this complaint:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&ei->i_data_sem);
                                lock(&s->s_dquot.dqio_mutex);
                                lock(&ei->i_data_sem);
   lock(&s->s_dquot.dqio_mutex);

Google-Bug-Id: 27907753

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 95dfff88de113bf35b32022858b4640319f6a2ae..15213a567301d12f2dbb1a8641a20f417c52206d 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -812,6 +812,29 @@ do {                                                                              \
 
 #include "extents_status.h"
 
+/*
+ * Lock subclasses for i_data_sem in the ext4_inode_info structure.
+ *
+ * These are needed to avoid lockdep false positives when we need to
+ * allocate blocks to the quota inode during ext4_map_blocks(), while
+ * holding i_data_sem for a normal (non-quota) inode.  Since we don't
+ * do quota tracking for the quota inode, this avoids deadlock (as
+ * well as infinite recursion, since it isn't turtles all the way
+ * down...)
+ *
+ *  I_DATA_SEM_NORMAL - Used for most inodes
+ *  I_DATA_SEM_OTHER  - Used by move_inode.c for the second normal inode
+ *                       where the second inode has larger inode number
+ *                       than the first
+ *  I_DATA_SEM_QUOTA  - Used for quota inodes only
+ */
+enum {
+       I_DATA_SEM_NORMAL = 0,
+       I_DATA_SEM_OTHER,
+       I_DATA_SEM_QUOTA,
+};
+
+
 /*
  * fourth extended file system inode data in memory
  */

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 3fb92abe57079af570100e80707c617bf2781c98..bd059e98548592f8bb35bd832b1e74e73a51ea4a 100644 (file)
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -60,10 +60,10 @@ ext4_double_down_write_data_sem(struct inode *first, struct inode *second)
 {
        if (first < second) {
                down_write(&EXT4_I(first)->i_data_sem);
-               down_write_nested(&EXT4_I(second)->i_data_sem, SINGLE_DEPTH_NESTING);
+               down_write_nested(&EXT4_I(second)->i_data_sem, I_DATA_SEM_OTHER);
        } else {
                down_write(&EXT4_I(second)->i_data_sem);
-               down_write_nested(&EXT4_I(first)->i_data_sem, SINGLE_DEPTH_NESTING);
+               down_write_nested(&EXT4_I(first)->i_data_sem, I_DATA_SEM_OTHER);
 
        }
 }
@@ -487,6 +487,13 @@ mext_check_arguments(struct inode *orig_inode,
                return -EBUSY;
        }
 
+       if (IS_NOQUOTA(orig_inode) || IS_NOQUOTA(donor_inode)) {
+               ext4_debug("ext4 move extent: The argument files should "
+                       "not be quota files [ino:orig %lu, donor %lu]\n",
+                       orig_inode->i_ino, donor_inode->i_ino);
+               return -EBUSY;
+       }
+
        /* Ext4 move extent supports only extent based file */
        if (!(ext4_test_inode_flag(orig_inode, EXT4_INODE_EXTENTS))) {
                ext4_debug("ext4 move extent: orig file is not extents "

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6f5ca3e92246b6acb97eb6b4c0d63099a83942e6..0d284635ef3cdcfc12fbaad7072393976a8a3555 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5272,6 +5272,20 @@ static int ext4_quota_on_mount(struct super_block *sb, int type)
                                        EXT4_SB(sb)->s_jquota_fmt, type);
 }
 
+static void lockdep_set_quota_inode(struct inode *inode, int subclass)
+{
+       struct ext4_inode_info *ei = EXT4_I(inode);
+
+       /* The first argument of lockdep_set_subclass has to be
+        * *exactly* the same as the argument to init_rwsem() --- in
+        * this case, in init_once() --- or lockdep gets unhappy
+        * because the name of the lock is set using the
+        * stringification of the argument to init_rwsem().
+        */
+       (void) ei;      /* shut up clang warning if !CONFIG_LOCKDEP */
+       lockdep_set_subclass(&ei->i_data_sem, subclass);
+}
+
 /*
  * Standard function to be called on quota_on
  */
@@ -5311,8 +5325,12 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
                if (err)
                        return err;
        }
-
-       return dquot_quota_on(sb, type, format_id, path);
+       lockdep_set_quota_inode(path->dentry->d_inode, I_DATA_SEM_QUOTA);
+       err = dquot_quota_on(sb, type, format_id, path);
+       if (err)
+               lockdep_set_quota_inode(path->dentry->d_inode,
+                                            I_DATA_SEM_NORMAL);
+       return err;
 }
 
 static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
@@ -5338,8 +5356,11 @@ static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
 
        /* Don't account quota for quota files to avoid recursion */
        qf_inode->i_flags |= S_NOQUOTA;
+       lockdep_set_quota_inode(qf_inode, I_DATA_SEM_QUOTA);
        err = dquot_enable(qf_inode, type, format_id, flags);
        iput(qf_inode);
+       if (err)
+               lockdep_set_quota_inode(qf_inode, I_DATA_SEM_NORMAL);
 
        return err;
 }