On 2021/04/24 2:30, Jan Kara wrote:
> Use invalidate_lock instead of zonefs' private i_mmap_sem. The intended
> purpose is exactly the same. By this conversion we also fix a race
> between hole punching and read(2) / readahead(2) paths that can lead to
> stale page cache contents.
zonefs does not support hole punching since the blocks of a file are determined
by the device zone configuration and cannot change, ever. So I think you can
remove the second sentence above.
>
> CC: Damien Le Moal <damien.lemoal@xxxxxxx>
> CC: Johannes Thumshirn <jth@xxxxxxxxxx>
> CC: <linux-fsdevel@xxxxxxxxxxxxxxx>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/zonefs/super.c | 23 +++++------------------
> fs/zonefs/zonefs.h | 7 +++----
> 2 files changed, 8 insertions(+), 22 deletions(-)
>
> diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
> index 049e36c69ed7..60ac5587c880 100644
> --- a/fs/zonefs/super.c
> +++ b/fs/zonefs/super.c
> @@ -462,7 +462,7 @@ static int zonefs_file_truncate(struct inode *inode, loff_t isize)
> inode_dio_wait(inode);
>
> /* Serialize against page faults */
> - down_write(&zi->i_mmap_sem);
> + down_write(&inode->i_mapping->invalidate_lock);
>
> /* Serialize against zonefs_iomap_begin() */
> mutex_lock(&zi->i_truncate_mutex);
> @@ -500,7 +500,7 @@ static int zonefs_file_truncate(struct inode *inode, loff_t isize)
>
> unlock:
> mutex_unlock(&zi->i_truncate_mutex);
> - up_write(&zi->i_mmap_sem);
> + up_write(&inode->i_mapping->invalidate_lock);
>
> return ret;
> }
> @@ -575,18 +575,6 @@ static int zonefs_file_fsync(struct file *file, loff_t start, loff_t end,
> return ret;
> }
>
> -static vm_fault_t zonefs_filemap_fault(struct vm_fault *vmf)
> -{
> - struct zonefs_inode_info *zi = ZONEFS_I(file_inode(vmf->vma->vm_file));
> - vm_fault_t ret;
> -
> - down_read(&zi->i_mmap_sem);
> - ret = filemap_fault(vmf);
> - up_read(&zi->i_mmap_sem);
> -
> - return ret;
> -}
> -
> static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
> {
> struct inode *inode = file_inode(vmf->vma->vm_file);
> @@ -607,16 +595,16 @@ static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
> file_update_time(vmf->vma->vm_file);
>
> /* Serialize against truncates */
> - down_read(&zi->i_mmap_sem);
> + down_read(&inode->i_mapping->invalidate_lock);
> ret = iomap_page_mkwrite(vmf, &zonefs_iomap_ops);
> - up_read(&zi->i_mmap_sem);
> + up_read(&inode->i_mapping->invalidate_lock);
>
> sb_end_pagefault(inode->i_sb);
> return ret;
> }
>
> static const struct vm_operations_struct zonefs_file_vm_ops = {
> - .fault = zonefs_filemap_fault,
> + .fault = filemap_fault,
> .map_pages = filemap_map_pages,
> .page_mkwrite = zonefs_filemap_page_mkwrite,
> };
> @@ -1158,7 +1146,6 @@ static struct inode *zonefs_alloc_inode(struct super_block *sb)
>
> inode_init_once(&zi->i_vnode);
> mutex_init(&zi->i_truncate_mutex);
> - init_rwsem(&zi->i_mmap_sem);
> zi->i_wr_refcnt = 0;
>
> return &zi->i_vnode;
> diff --git a/fs/zonefs/zonefs.h b/fs/zonefs/zonefs.h
> index 51141907097c..7b147907c328 100644
> --- a/fs/zonefs/zonefs.h
> +++ b/fs/zonefs/zonefs.h
> @@ -70,12 +70,11 @@ struct zonefs_inode_info {
> * and changes to the inode private data, and in particular changes to
> * a sequential file size on completion of direct IO writes.
> * Serialization of mmap read IOs with truncate and syscall IO
> - * operations is done with i_mmap_sem in addition to i_truncate_mutex.
> - * Only zonefs_seq_file_truncate() takes both lock (i_mmap_sem first,
> - * i_truncate_mutex second).
> + * operations is done with invalidate_lock in addition to
> + * i_truncate_mutex. Only zonefs_seq_file_truncate() takes both lock
> + * (invalidate_lock first, i_truncate_mutex second).
> */
> struct mutex i_truncate_mutex;
> - struct rw_semaphore i_mmap_sem;
>
> /* guarded by i_truncate_mutex */
> unsigned int i_wr_refcnt;
>
--
Damien Le Moal
Western Digital Research
