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Date: Wed, 6 Feb 2008 14:19:28 +0100
From: Jan Kara <jack@...e.cz>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc: tytso@....edu, cmm@...ibm.com, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: Fix circular locking dependency with migrate and
rm.
On Wed 06-02-08 16:30:04, Aneesh Kumar K.V wrote:
> We now take inode->i_mutex lock to prevent any update of the inode i_data
> field. Before we switch the inode format we take i_data_sem to prevent
> parallel read.
>
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.24-rc8 #6
> -------------------------------------------------------
> rm/2401 is trying to acquire lock:
> (&ei->i_data_sem){----}, at: [<c01dca58>] ext4_get_blocks_wrap+0x21/0x108
>
> but task is already holding lock:
> (jbd2_handle){--..}, at: [<c01fc4a7>] jbd2_journal_start+0xd2/0xff
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (jbd2_handle){--..}:
> [<c0143a5c>] __lock_acquire+0xa31/0xc1a
> [<c0143cbf>] lock_acquire+0x7a/0x94
> [<c01fc4ca>] jbd2_journal_start+0xf5/0xff
> [<c01e3539>] ext4_journal_start_sb+0x48/0x4a
> [<c01eb980>] ext4_ext_migrate+0x7d/0x535
> [<c01df328>] ext4_ioctl+0x528/0x56c
> [<c0177700>] do_ioctl+0x50/0x67
> [<c017794e>] vfs_ioctl+0x237/0x24a
> [<c0177992>] sys_ioctl+0x31/0x4b
> [<c0104f8a>] sysenter_past_esp+0x5f/0xa5
> [<ffffffff>] 0xffffffff
>
> -> #0 (&ei->i_data_sem){----}:
> [<c014394c>] __lock_acquire+0x921/0xc1a
> [<c0143cbf>] lock_acquire+0x7a/0x94
> [<c044f247>] down_read+0x42/0x79
> [<c01dca58>] ext4_get_blocks_wrap+0x21/0x108
> [<c01dcba1>] ext4_getblk+0x62/0x1c4
> [<c01e0de9>] ext4_find_entry+0x350/0x5b7
> [<c01e200c>] ext4_unlink+0x6e/0x1a4
> [<c017449e>] vfs_unlink+0x49/0x89
> [<c0175f02>] do_unlinkat+0x96/0x12c
> [<c0175fa8>] sys_unlink+0x10/0x12
> [<c0104f8a>] sysenter_past_esp+0x5f/0xa5
> [<ffffffff>] 0xffffffff
>
> other info that might help us debug this:
>
> 3 locks held by rm/2401:
> #0: (&type->i_mutex_dir_key#5/1){--..}, at: [<c0175eca>] do_unlinkat+0x5e/0x12c
> #1: (&sb->s_type->i_mutex_key#8){--..}, at: [<c017448b>] vfs_unlink+0x36/0x89
> #2: (jbd2_handle){--..}, at: [<c01fc4a7>] jbd2_journal_start+0xd2/0xff
>
> stack backtrace:
> Pid: 2401, comm: rm Not tainted 2.6.24-rc8 #6
> [<c0106017>] show_trace_log_lvl+0x1a/0x2f
> [<c0106893>] show_trace+0x12/0x14
> [<c0106b89>] dump_stack+0x6c/0x72
> [<c0141b26>] print_circular_bug_tail+0x5f/0x68
> [<c014394c>] __lock_acquire+0x921/0xc1a
> [<c0143cbf>] lock_acquire+0x7a/0x94
> [<c044f247>] down_read+0x42/0x79
> [<c01dca58>] ext4_get_blocks_wrap+0x21/0x108
> [<c01dcba1>] ext4_getblk+0x62/0x1c4
> [<c01e0de9>] ext4_find_entry+0x350/0x5b7
> [<c01e200c>] ext4_unlink+0x6e/0x1a4
> [<c017449e>] vfs_unlink+0x49/0x89
> [<c0175f02>] do_unlinkat+0x96/0x12c
> [<c0175fa8>] sys_unlink+0x10/0x12
> [<c0104f8a>] sysenter_past_esp+0x5f/0xa5
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Add Acked-by: Jan Kara <jack@...e.cz> if you wish.
Honza
> ---
> fs/ext4/migrate.c | 117 +++++++++++++++++++++++++++++++++-------------------
> 1 files changed, 74 insertions(+), 43 deletions(-)
>
> diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> index 9ee1f7c..8c6c685 100644
> --- a/fs/ext4/migrate.c
> +++ b/fs/ext4/migrate.c
> @@ -61,10 +61,9 @@ static int finish_range(handle_t *handle, struct inode *inode,
> retval = ext4_journal_restart(handle, needed);
> if (retval)
> goto err_out;
> - }
> - if (needed) {
> + } else if (needed) {
> retval = ext4_journal_extend(handle, needed);
> - if (retval != 0) {
> + if (retval) {
> /*
> * IF not able to extend the journal restart the journal
> */
> @@ -220,6 +219,26 @@ static int update_tind_extent_range(handle_t *handle, struct inode *inode,
>
> }
>
> +static int extend_credit_for_blkdel(handle_t *handle, struct inode *inode)
> +{
> + int retval = 0, needed;
> +
> + if (handle->h_buffer_credits > EXT4_RESERVE_TRANS_BLOCKS)
> + return 0;
> + /*
> + * We are freeing a blocks. During this we touch
> + * superblock, group descriptor and block bitmap.
> + * So allocate a credit of 3. We may update
> + * quota (user and group).
> + */
> + needed = 3 + 2*EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb);
> +
> + if (ext4_journal_extend(handle, needed) != 0)
> + retval = ext4_journal_restart(handle, needed);
> +
> + return retval;
> +}
> +
> static int free_dind_blocks(handle_t *handle,
> struct inode *inode, __le32 i_data)
> {
> @@ -234,11 +253,14 @@ static int free_dind_blocks(handle_t *handle,
>
> tmp_idata = (__le32 *)bh->b_data;
> for (i = 0; i < max_entries; i++) {
> - if (tmp_idata[i])
> + if (tmp_idata[i]) {
> + extend_credit_for_blkdel(handle, inode);
> ext4_free_blocks(handle, inode,
> le32_to_cpu(tmp_idata[i]), 1, 1);
> + }
> }
> put_bh(bh);
> + extend_credit_for_blkdel(handle, inode);
> ext4_free_blocks(handle, inode, le32_to_cpu(i_data), 1, 1);
> return 0;
> }
> @@ -267,29 +289,32 @@ static int free_tind_blocks(handle_t *handle,
> }
> }
> put_bh(bh);
> + extend_credit_for_blkdel(handle, inode);
> ext4_free_blocks(handle, inode, le32_to_cpu(i_data), 1, 1);
> return 0;
> }
>
> -static int free_ind_block(handle_t *handle, struct inode *inode)
> +static int free_ind_block(handle_t *handle, struct inode *inode, __le32 *i_data)
> {
> int retval;
> - struct ext4_inode_info *ei = EXT4_I(inode);
>
> - if (ei->i_data[EXT4_IND_BLOCK])
> + /* ei->i_data[EXT4_IND_BLOCK] */
> + if (i_data[0]) {
> + extend_credit_for_blkdel(handle, inode);
> ext4_free_blocks(handle, inode,
> - le32_to_cpu(ei->i_data[EXT4_IND_BLOCK]), 1, 1);
> + le32_to_cpu(i_data[0]), 1, 1);
> + }
>
> - if (ei->i_data[EXT4_DIND_BLOCK]) {
> - retval = free_dind_blocks(handle, inode,
> - ei->i_data[EXT4_DIND_BLOCK]);
> + /* ei->i_data[EXT4_DIND_BLOCK] */
> + if (i_data[1]) {
> + retval = free_dind_blocks(handle, inode, i_data[1]);
> if (retval)
> return retval;
> }
>
> - if (ei->i_data[EXT4_TIND_BLOCK]) {
> - retval = free_tind_blocks(handle, inode,
> - ei->i_data[EXT4_TIND_BLOCK]);
> + /* ei->i_data[EXT4_TIND_BLOCK] */
> + if (i_data[2]) {
> + retval = free_tind_blocks(handle, inode, i_data[2]);
> if (retval)
> return retval;
> }
> @@ -297,15 +322,13 @@ static int free_ind_block(handle_t *handle, struct inode *inode)
> }
>
> static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
> - struct inode *tmp_inode, int retval)
> + struct inode *tmp_inode)
> {
> + int retval;
> + __le32 i_data[3];
> struct ext4_inode_info *ei = EXT4_I(inode);
> struct ext4_inode_info *tmp_ei = EXT4_I(tmp_inode);
>
> - retval = free_ind_block(handle, inode);
> - if (retval)
> - goto err_out;
> -
> /*
> * One credit accounted for writing the
> * i_data field of the original inode
> @@ -317,6 +340,11 @@ static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
> goto err_out;
> }
>
> + i_data[0] = ei->i_data[EXT4_IND_BLOCK];
> + i_data[1] = ei->i_data[EXT4_DIND_BLOCK];
> + i_data[2] = ei->i_data[EXT4_TIND_BLOCK];
> +
> + down_write(&EXT4_I(inode)->i_data_sem);
> /*
> * We have the extent map build with the tmp inode.
> * Now copy the i_data across
> @@ -336,8 +364,15 @@ static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
> spin_lock(&inode->i_lock);
> inode->i_blocks += tmp_inode->i_blocks;
> spin_unlock(&inode->i_lock);
> + up_write(&EXT4_I(inode)->i_data_sem);
>
> + /*
> + * We mark the inode dirty after, because we decrement the
> + * i_blocks when freeing the indirect meta-data blocks
> + */
> + retval = free_ind_block(handle, inode, i_data);
> ext4_mark_inode_dirty(handle, inode);
> +
> err_out:
> return retval;
> }
> @@ -365,6 +400,7 @@ static int free_ext_idx(handle_t *handle, struct inode *inode,
> }
> }
> put_bh(bh);
> + extend_credit_for_blkdel(handle, inode);
> ext4_free_blocks(handle, inode, block, 1, 1);
> return retval;
> }
> @@ -420,7 +456,6 @@ int ext4_ext_migrate(struct inode *inode, struct file *filp,
> */
> return retval;
>
> - down_write(&EXT4_I(inode)->i_data_sem);
> handle = ext4_journal_start(inode,
> EXT4_DATA_TRANS_BLOCKS(inode->i_sb) +
> EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
> @@ -454,13 +489,6 @@ int ext4_ext_migrate(struct inode *inode, struct file *filp,
> ext4_orphan_add(handle, tmp_inode);
> ext4_journal_stop(handle);
>
> - ei = EXT4_I(inode);
> - i_data = ei->i_data;
> - memset(&lb, 0, sizeof(lb));
> -
> - /* 32 bit block address 4 bytes */
> - max_entries = inode->i_sb->s_blocksize >> 2;
> -
> /*
> * start with one credit accounted for
> * superblock modification.
> @@ -469,7 +497,20 @@ int ext4_ext_migrate(struct inode *inode, struct file *filp,
> * trascation that created the inode. Later as and
> * when we add extents we extent the journal
> */
> + /*
> + * inode_mutex prevent write and truncate on the file. Read still goes
> + * through. We take i_data_sem in ext4_ext_swap_inode_data before we
> + * switch the inode format to prevent read.
> + */
> + mutex_lock(&(inode->i_mutex));
> handle = ext4_journal_start(inode, 1);
> +
> + ei = EXT4_I(inode);
> + i_data = ei->i_data;
> + memset(&lb, 0, sizeof(lb));
> +
> + /* 32 bit block address 4 bytes */
> + max_entries = inode->i_sb->s_blocksize >> 2;
> for (i = 0; i < EXT4_NDIR_BLOCKS; i++, blk_count++) {
> if (i_data[i]) {
> retval = update_extent_range(handle, tmp_inode,
> @@ -507,19 +548,6 @@ int ext4_ext_migrate(struct inode *inode, struct file *filp,
> */
> retval = finish_range(handle, tmp_inode, &lb);
> err_out:
> - /*
> - * We are either freeing extent information or indirect
> - * blocks. During this we touch superblock, group descriptor
> - * and block bitmap. Later we mark the tmp_inode dirty
> - * via ext4_ext_tree_init. So allocate a credit of 4
> - * We may update quota (user and group).
> - *
> - * FIXME!! we may be touching bitmaps in different block groups.
> - */
> - if (ext4_journal_extend(handle,
> - 4 + 2*EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb)) != 0)
> - ext4_journal_restart(handle,
> - 4 + 2*EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb));
> if (retval)
> /*
> * Failure case delete the extent information with the
> @@ -528,7 +556,11 @@ err_out:
> free_ext_block(handle, tmp_inode);
> else
> retval = ext4_ext_swap_inode_data(handle, inode,
> - tmp_inode, retval);
> + tmp_inode);
> +
> + /* We mark the tmp_inode dirty via ext4_ext_tree_init. */
> + if (ext4_journal_extend(handle, 1) != 0)
> + ext4_journal_restart(handle, 1);
>
> /*
> * Mark the tmp_inode as of size zero
> @@ -556,8 +588,7 @@ err_out:
> tmp_inode->i_nlink = 0;
>
> ext4_journal_stop(handle);
> -
> - up_write(&EXT4_I(inode)->i_data_sem);
> + mutex_unlock(&(inode->i_mutex));
>
> if (tmp_inode)
> iput(tmp_inode);
> --
> 1.5.4.23.gef5b9-dirty
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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