Re: [PATCH 5/7] add llseek_nowait support for xfs

Hao Xu
2023-07-27T12:28:34Z

On 7/27/23 06:14, Dave Chinner wrote:
> On Wed, Jul 26, 2023 at 06:26:01PM +0800, Hao Xu wrote:
>> From: Hao Xu <howeyxu@tencent.com>
>>
>> Add llseek_nowait() operation for xfs, it acts just like llseek(). The
>> thing different is it delivers nowait parameter to iomap layer.
>>
>> Signed-off-by: Hao Xu <howeyxu@tencent.com>
>> ---
>> fs/xfs/xfs_file.c | 29 +++++++++++++++++++++++++++--
>> 1 file changed, 27 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
>> index 73adc0aee2ff..cba82264221d 100644
>> --- a/fs/xfs/xfs_file.c
>> +++ b/fs/xfs/xfs_file.c
>> @@ -1257,10 +1257,11 @@ xfs_file_readdir(
>> }
>>
>> STATIC loff_t
>> -xfs_file_llseek(
>> +__xfs_file_llseek(
>> struct file *file,
>> loff_t offset,
>> - int whence)
>> + int whence,
>> + bool nowait)
>> {
>> struct inode *inode = file->f_mapping->host;
>>
>> @@ -1282,6 +1283,28 @@ xfs_file_llseek(
>> return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
>> }
>>
>> +STATIC loff_t
>> +xfs_file_llseek(
>> + struct file *file,
>> + loff_t offset,
>> + int whence)
>> +{
>> + return __xfs_file_llseek(file, offset, whence, false);
>> +}
>> +
>> +STATIC loff_t
>> +xfs_file_llseek_nowait(
>> + struct file *file,
>> + loff_t offset,
>> + int whence,
>> + bool nowait)
>> +{
>> + if (file->f_op == &xfs_file_operations)
>> + return __xfs_file_llseek(file, offset, whence, nowait);
>> + else
>> + return generic_file_llseek(file, offset, whence);
>> +}
>> +
>> #ifdef CONFIG_FS_DAX
>> static inline vm_fault_t
>> xfs_dax_fault(
>> @@ -1442,6 +1465,7 @@ xfs_file_mmap(
>>
>> const struct file_operations xfs_file_operations = {
>> .llseek = xfs_file_llseek,
>> + .llseek_nowait = xfs_file_llseek_nowait,
>> .read_iter = xfs_file_read_iter,
>> .write_iter = xfs_file_write_iter,
>> .splice_read = xfs_file_splice_read,
>> @@ -1467,6 +1491,7 @@ const struct file_operations xfs_dir_file_operations = {
>> .read = generic_read_dir,
>> .iterate_shared = xfs_file_readdir,
>> .llseek = generic_file_llseek,
>> + .llseek_nowait = xfs_file_llseek_nowait,
>> .unlocked_ioctl = xfs_file_ioctl,
>> #ifdef CONFIG_COMPAT
>> .compat_ioctl = xfs_file_compat_ioctl,
>
> This is pretty nasty. It would be far better just to change the
> .llseek method than to inflict this on every filesystem for the
> forseeable future.
>
> Not that I'm a fan of passing "nowait" booleans all through the file
> operations methods - that way lies madness. We use a control
> structure for the IO path operations (kiocb) to hold per-call
> context information, perhaps we need something similar for these
> other methods that people are wanting to hook up to io_uring (e.g.
> readdir) so taht we don't have to play whack-a-mole with every new
> io_uring method that people want and then end up with a different
> nowait solution for every method.
>
> -Dave.

whack-a-mole is exactly what I thought when I tried to find a place to
hold that...I'll think about it in next version, a generic structure for
io_uring is good I believe. I'll update this patchset after the getdents
stuff are merged.

Thanks,
Hao