[Ocfs2-devel] [PATCH v3] ocfs2: the ip_alloc_sem should be taken in ocfs2_get_block()
Joseph Qi
jiangqi903 at gmail.com
Tue Oct 24 18:15:23 PDT 2017
On 17/10/24 20:46, alex chen wrote:
> The ip_alloc_sem should be taken in ocfs2_get_block() when reading file
> in DIRECT mode to prevent concurrent access to extent tree with
> ocfs2_dio_end_io_write(), which may cause BUGON in the following situation:
>
> read file 'A' end_io of writing file 'A'
> vfs_read
> __vfs_read
> ocfs2_file_read_iter
> generic_file_read_iter
> ocfs2_direct_IO
> __blockdev_direct_IO
> do_blockdev_direct_IO
> do_direct_IO
> get_more_blocks
> ocfs2_get_block
> ocfs2_extent_map_get_blocks
> ocfs2_get_clusters
> ocfs2_get_clusters_nocache()
> ocfs2_search_extent_list
> return the index of record which
> contains the v_cluster, that is
> v_cluster > rec[i]->e_cpos.
> ocfs2_dio_end_io
> ocfs2_dio_end_io_write
> down_write(&oi->ip_alloc_sem);
> ocfs2_mark_extent_written
> ocfs2_change_extent_flag
> ocfs2_split_extent
> ...
> --> modify the rec[i]->e_cpos, resulting
> in v_cluster < rec[i]->e_cpos.
> BUG_ON(v_cluster < le32_to_cpu(rec->e_cpos))
>
> Fixes: c15471f79506 ("ocfs2: fix sparse file & data ordering issue in direct io")
>
> Signed-off-by: Alex Chen <alex.chen at huawei.com>
> Reviewed-by: Jun Piao <piaojun at huawei.com>
> Acked-by: Changwei Ge <ge.changwei at h3c.com>>
I don't think we have to rename ocfs2_dio_get_block. Anyway it doesn't
matter.
Reviewed-by: Joseph Qi <jiangqi903 at gmail.com>
> ---
> fs/ocfs2/aops.c | 26 ++++++++++++++++++--------
> 1 file changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index 88a31e9..d151632 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -134,6 +134,19 @@ static int ocfs2_symlink_get_block(struct inode *inode, sector_t iblock,
> return err;
> }
>
> +static int ocfs2_lock_get_block(struct inode *inode, sector_t iblock,
> + struct buffer_head *bh_result, int create)
> +{
> + int ret = 0;
> + struct ocfs2_inode_info *oi = OCFS2_I(inode);
> +
> + down_read(&oi->ip_alloc_sem);
> + ret = ocfs2_get_block(inode, iblock, bh_result, create);
> + up_read(&oi->ip_alloc_sem);
> +
> + return ret;
> +}
> +
> int ocfs2_get_block(struct inode *inode, sector_t iblock,
> struct buffer_head *bh_result, int create)
> {
> @@ -2128,7 +2141,7 @@ static void ocfs2_dio_free_write_ctx(struct inode *inode,
> * called like this: dio->get_blocks(dio->inode, fs_startblk,
> * fs_count, map_bh, dio->rw == WRITE);
> */
> -static int ocfs2_dio_get_block(struct inode *inode, sector_t iblock,
> +static int ocfs2_dio_wr_get_block(struct inode *inode, sector_t iblock,
> struct buffer_head *bh_result, int create)
> {
> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> @@ -2154,12 +2167,9 @@ static int ocfs2_dio_get_block(struct inode *inode, sector_t iblock,
> * while file size will be changed.
> */
> if (pos + total_len <= i_size_read(inode)) {
> - down_read(&oi->ip_alloc_sem);
> - /* This is the fast path for re-write. */
> - ret = ocfs2_get_block(inode, iblock, bh_result, create);
> -
> - up_read(&oi->ip_alloc_sem);
>
> + /* This is the fast path for re-write. */
> + ret = ocfs2_lock_get_block(inode, iblock, bh_result, create);
> if (buffer_mapped(bh_result) &&
> !buffer_new(bh_result) &&
> ret == 0)
> @@ -2424,9 +2434,9 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
> return 0;
>
> if (iov_iter_rw(iter) == READ)
> - get_block = ocfs2_get_block;
> + get_block = ocfs2_lock_get_block;
> else
> - get_block = ocfs2_dio_get_block;
> + get_block = ocfs2_dio_wr_get_block;
>
> return __blockdev_direct_IO(iocb, inode, inode->i_sb->s_bdev,
> iter, get_block,
>
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