Re: [PATCH v10 6/7] nfs/localio: add tracepoints for misaligned DIO READ and WRITE support

[Anna Schumaker <anna.schumaker@oracle.com>]

On 9/18/25 1:46 PM, Mike Snitzer wrote:
> On Thu, Sep 18, 2025 at 01:33:30PM -0400, Anna Schumaker wrote:
>> Hi Mike,
>>
>> On 9/17/25 2:18 PM, Mike Snitzer wrote:
>>> Add nfs_local_dio_class and use it to create nfs_local_dio_read,
>>> nfs_local_dio_write and nfs_local_dio_misaligned trace events.
>>>
>>> These trace events show how NFS LOCALIO splits a given misaligned
>>> IO into a mix of misaligned head and/or tail extents and a DIO-aligned
>>> middle extent.  The misaligned head and/or tail extents are issued
>>> using buffered IO and the DIO-aligned middle is issued using O_DIRECT.
>>>
>>> This combination of trace events is useful for LOCALIO DIO READs:
>>>
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_read/enable
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_misaligned/enable
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_initiate_read/enable
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_readpage_done/enable
>>>   echo 1 > /sys/kernel/tracing/events/xfs/xfs_file_direct_read/enable
>>>
>>> This combination of trace events is useful for LOCALIO DIO WRITEs:
>>>
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_write/enable
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_local_dio_misaligned/enable
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_initiate_write/enable
>>>   echo 1 > /sys/kernel/tracing/events/nfs/nfs_writeback_done/enable
>>>   echo 1 > /sys/kernel/tracing/events/xfs/xfs_file_direct_write/enable
>>
>> I'm having a lot of trouble compiling this patch. I'm seeing errors like this:
>>
>>
>> fs/nfs/nfstrace.h:1800:1: error: declaration of 'struct nfs_local_dio' will not be visible outside of this function [-Werror,-Wvisibility]
>>  1800 | DEFINE_NFS_LOCAL_DIO_EVENT(write);
>>       | ^
>> fs/nfs/nfstrace.h:1796:17: note: expanded from macro 'DEFINE_NFS_LOCAL_DIO_EVENT'
>>  1796 |                  const struct nfs_local_dio *local_dio),\
>>       |                               ^
>> fs/nfs/nfstrace.h:1800:1: error: declaration of 'struct nfs_local_dio' will not be visible outside of this function [-Werror,-Wvisibility]
>> fs/nfs/nfstrace.h:1796:17: note: expanded from macro 'DEFINE_NFS_LOCAL_DIO_EVENT'
>>  1796 |                  const struct nfs_local_dio *local_dio),\
>>       |                               ^
>> fs/nfs/nfstrace.h:1800:1: error: declaration of 'struct nfs_local_dio' will not be visible outside of this function [-Werror,-Wvisibility]
>> fs/nfs/nfstrace.h:1796:17: note: expanded from macro 'DEFINE_NFS_LOCAL_DIO_EVENT'
>>  1796 |                  const struct nfs_local_dio *local_dio),\
>>       |                               ^
>> fs/nfs/nfstrace.h:1800:1: error: declaration of 'struct nfs_local_dio' will not be visible outside of this function [-Werror,-Wvisibility]
>> fs/nfs/nfstrace.h:1796:17: note: expanded from macro 'DEFINE_NFS_LOCAL_DIO_EVENT'
>>  1796 |                  const struct nfs_local_dio *local_dio),\
>>       |                               ^
>> fs/nfs/nfstrace.h:1800:1: error: declaration of 'struct nfs_local_dio' will not be visible outside of this function [-Werror,-Wvisibility]
>> fs/nfs/nfstrace.h:1796:17: note: expanded from macro 'DEFINE_NFS_LOCAL_DIO_EVENT'
>>  1796 |                  const struct nfs_local_dio *local_dio),\
>>       |                               ^
>> fs/nfs/nfstrace.h:1800:1: error: declaration of 'struct nfs_local_dio' will not be visible outside of this function [-Werror,-Wvisibility]
>> fs/nfs/nfstrace.h:1796:17: note: expanded from macro 'DEFINE_NFS_LOCAL_DIO_EVENT'
>>  1796 |                  const struct nfs_local_dio *local_dio),\
>>       |                               ^
>> fs/nfs/nfstrace.h:1800:1: error: declaration of 'struct nfs_local_dio' will not be visible outside of this function [-Werror,-Wvisibility]
>> fs/nfs/nfstrace.h:1796:17: note: expanded from macro 'DEFINE_NFS_LOCAL_DIO_EVENT'
>>  1796 |                  const struct nfs_local_dio *local_dio),\
>>       |                               ^
>> fs/nfs/nfstrace.h:1800:1: error: incompatible pointer types passing 'const struct nfs_local_dio *' to parameter of type 'const struct nfs_local_dio *' [-Werror,-Wincompatible-pointer-types]
>>  1800 | DEFINE_NFS_LOCAL_DIO_EVENT(write);
>>
>>
>> Am I missing a patch somewhere along the line?
>>
>> Thanks,
>> Anna
>>
>>>
>>> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
>>> ---
>>>  fs/nfs/internal.h | 10 +++++++
>>>  fs/nfs/localio.c  | 19 ++++++-------
>>>  fs/nfs/nfs3xdr.c  |  2 +-
>>>  fs/nfs/nfstrace.h | 70 +++++++++++++++++++++++++++++++++++++++++++++++
>>>  4 files changed, 89 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
>>> index d44233cfd7949..3d380c45b5ef3 100644
>>> --- a/fs/nfs/internal.h
>>> +++ b/fs/nfs/internal.h
>>> @@ -456,6 +456,16 @@ extern int nfs_wait_bit_killable(struct wait_bit_key *key, int mode);
>>>  
>>>  #if IS_ENABLED(CONFIG_NFS_LOCALIO)
>>>  /* localio.c */
>>> +struct nfs_local_dio {
>>> +	u32 mem_align;
>>> +	u32 offset_align;
>>> +	loff_t middle_offset;
>>> +	loff_t end_offset;
>>> +	ssize_t	start_len;	/* Length for misaligned first extent */
>>> +	ssize_t	middle_len;	/* Length for DIO-aligned middle extent */
>>> +	ssize_t	end_len;	/* Length for misaligned last extent */
>>> +};
>>> +
>>>  extern void nfs_local_probe_async(struct nfs_client *);
>>>  extern void nfs_local_probe_async_work(struct work_struct *);
>>>  extern struct nfsd_file *nfs_local_open_fh(struct nfs_client *,
>>> diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
>>> index 768af570183af..cf1533759646e 100644
>>> --- a/fs/nfs/localio.c
>>> +++ b/fs/nfs/localio.c
>>> @@ -322,16 +322,6 @@ nfs_local_iocb_alloc(struct nfs_pgio_header *hdr,
>>>  	return iocb;
>>>  }
>>>  
>>> -struct nfs_local_dio {
>>> -	u32 mem_align;
>>> -	u32 offset_align;
>>> -	loff_t middle_offset;
>>> -	loff_t end_offset;
>>> -	ssize_t	start_len;	/* Length for misaligned first extent */
>>> -	ssize_t	middle_len;	/* Length for DIO-aligned middle extent */
>>> -	ssize_t	end_len;	/* Length for misaligned last extent */
>>> -};
>>> -
>>>  static bool
>>>  nfs_is_local_dio_possible(struct nfs_local_kiocb *iocb, int rw,
>>>  			  size_t len, struct nfs_local_dio *local_dio)
>>> @@ -367,6 +357,10 @@ nfs_is_local_dio_possible(struct nfs_local_kiocb *iocb, int rw,
>>>  	local_dio->middle_len = middle_end - start_end;
>>>  	local_dio->end_len = orig_end - middle_end;
>>>  
>>> +	if (rw == ITER_DEST)
>>> +		trace_nfs_local_dio_read(hdr->inode, offset, len, local_dio);
>>> +	else
>>> +		trace_nfs_local_dio_write(hdr->inode, offset, len, local_dio);
>>>  	return true;
>>>  }
>>>  
>>> @@ -446,8 +440,11 @@ nfs_local_iters_setup_dio(struct nfs_local_kiocb *iocb, int rw,
>>>  		nfs_iov_iter_aligned_bvec(&iters[n_iters],
>>>  			local_dio->mem_align-1, local_dio->offset_align-1);
>>>  
>>> -	if (unlikely(!iocb->iter_is_dio_aligned[n_iters]))
>>> +	if (unlikely(!iocb->iter_is_dio_aligned[n_iters])) {
>>> +		trace_nfs_local_dio_misaligned(iocb->hdr->inode,
>>> +			iocb->hdr->args.offset, len, local_dio);
>>>  		return 0; /* no DIO-aligned IO possible */
>>> +	}
>>>  	++n_iters;
>>>  
>>>  	iocb->n_iters = n_iters;
>>> diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
>>> index 4ae01c10b7e28..e17d729084125 100644
>>> --- a/fs/nfs/nfs3xdr.c
>>> +++ b/fs/nfs/nfs3xdr.c
>>> @@ -23,8 +23,8 @@
>>>  #include <linux/nfsacl.h>
>>>  #include <linux/nfs_common.h>
>>>  
>>> -#include "nfstrace.h"
>>>  #include "internal.h"
>>> +#include "nfstrace.h"
>>>  
>>>  #define NFSDBG_FACILITY		NFSDBG_XDR
>>>  
> 
> This change ^ was critical for fixing unknown type issues for 'struct
> nfs_local_dio' issues on my build. But I haven't seen the issue you've
> reported above. I'll try applying my changes on very latest upstream
> tree.
> 
> Which tree/branch are you using for your baseline?  Also, which
> version of gcc (which distro even) are you using?

I'm using my linux-next branch from: git.linux-nfs.org/projects/anna/linux-nfs.git.
It's v6.17-rc6 plus the patches I'm planning for the next merge window.

Anna

> 
> (I even tried including "internal.h" directly in "nfstrace.h" but that
> caused all sorts of different compiler issues). 
> 
> Thanks,
> Mike