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 5:03 PM, Mike Snitzer wrote:
> On Thu, Sep 18, 2025 at 04:18:49PM -0400, Mike Snitzer wrote:
>> On Thu, Sep 18, 2025 at 03:55:32PM -0400, Anna Schumaker wrote:
>>>
>>>
>>> On 9/18/25 3:21 PM, Mike Snitzer wrote:
>>>> On Thu, Sep 18, 2025 at 01:55:03PM -0400, Anna Schumaker wrote:
>>>>>
>>>>>
>>>>> 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);
>>
>> BTW, this ^ last incompatible pointer type error doesn't make any
>> sense.
>>
>> I'm concerned this is very specific to your development environment.
>>
>> (more reply below)
>>
>>>>>>>
>>>>>>>
>>>>>>> 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.
>>>>
>>>> Like I mentioned in another reply in this thread, I've pushed a tree
>>>> that is based on your linux-next branch here:
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/snitzer/linux.git/log/?h=anna-linux-next-6.18
>>>>
>>>> I've verified that this builds fine for me when using either:
>>>> EL8.10 with gcc 11.2.1-9
>>>> EL9.5 with 11.5.0-5
>>>>
>>>> Which distro and gcc version are you using?
>>>
>>> This is with Archlinux and clang v 20.1.8, although I do
>>> see similar errors with gcc 15.2.1.
>>
>> OK, so way more bleeding edge than my 2 versions of gcc 11.x
>>
>> I tried to see if disabling CONFIG_NFS_LOCALIO might explain it, but
>> that compiles fine for me too.
>>
>> Please feel free to share your .config with me off-list and I'll keep
>> chasing.
>>
> 
> FYI, I'm not seeing any compiler issues with gcc 15.1.1-2 (I updated
> my EL9 system to use gcc-toolset-15-15.0-9.el9.x86_64).
> 
> Please feel free to drop this nfstrace patch until we're able to
> figure out what's happening on your build environment.

Sounds good! I'll send you the .config I'm using privately if you want to try it out.

Anna

> 
> Thanks,
> Mike