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[PATCH v2 11/11] xfs: Allow block allocator to take an alignment hint

John Garry posted 11 patches 10 months, 1 week ago
There is a newer version of this series
[PATCH v2 11/11] xfs: Allow block allocator to take an alignment hint
Posted by John Garry 10 months, 1 week ago 
When issuing an atomic write by the CoW method, give the block allocator a
hint to naturally align the data blocks.

This means that we have a better chance to issuing the atomic write via
HW offload next time.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/libxfs/xfs_bmap.c | 7 ++++++-
 fs/xfs/libxfs/xfs_bmap.h | 6 +++++-
 fs/xfs/xfs_reflink.c     | 8 ++++++--
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 0ef19f1469ec..9bfdfb7cdcae 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3454,6 +3454,12 @@ xfs_bmap_compute_alignments(
 		align = xfs_get_cowextsz_hint(ap->ip);
 	else if (ap->datatype & XFS_ALLOC_USERDATA)
 		align = xfs_get_extsz_hint(ap->ip);
+
+	if (align > 1 && ap->flags & XFS_BMAPI_EXTSZALIGN)
+		args->alignment = align;
+	else
+		args->alignment = 1;
+
 	if (align) {
 		if (xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, align, 0,
 					ap->eof, 0, ap->conv, &ap->offset,
@@ -3782,7 +3788,6 @@ xfs_bmap_btalloc(
 		.wasdel		= ap->wasdel,
 		.resv		= XFS_AG_RESV_NONE,
 		.datatype	= ap->datatype,
-		.alignment	= 1,
 		.minalignslop	= 0,
 	};
 	xfs_fileoff_t		orig_offset;
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index 4b721d935994..7a31697331dc 100644
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -87,6 +87,9 @@ struct xfs_bmalloca {
 /* Do not update the rmap btree.  Used for reconstructing bmbt from rmapbt. */
 #define XFS_BMAPI_NORMAP	(1u << 10)
 
+/* Try to naturally align allocations to extsz hint */
+#define XFS_BMAPI_EXTSZALIGN	(1u << 11)
+
 #define XFS_BMAPI_FLAGS \
 	{ XFS_BMAPI_ENTIRE,	"ENTIRE" }, \
 	{ XFS_BMAPI_METADATA,	"METADATA" }, \
@@ -98,7 +101,8 @@ struct xfs_bmalloca {
 	{ XFS_BMAPI_REMAP,	"REMAP" }, \
 	{ XFS_BMAPI_COWFORK,	"COWFORK" }, \
 	{ XFS_BMAPI_NODISCARD,	"NODISCARD" }, \
-	{ XFS_BMAPI_NORMAP,	"NORMAP" }
+	{ XFS_BMAPI_NORMAP,	"NORMAP" },\
+	{ XFS_BMAPI_EXTSZALIGN,	"EXTSZALIGN" }
 
 
 static inline int xfs_bmapi_aflag(int w)
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index d097d33dc000..033dff86ecf0 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -445,6 +445,11 @@ xfs_reflink_fill_cow_hole(
 	int			nimaps;
 	int			error;
 	bool			found;
+	uint32_t		bmapi_flags = XFS_BMAPI_COWFORK |
+					      XFS_BMAPI_PREALLOC;
+
+	if (atomic)
+		bmapi_flags |= XFS_BMAPI_EXTSZALIGN;
 
 	resaligned = xfs_aligned_fsb_count(imap->br_startoff,
 		imap->br_blockcount, xfs_get_cowextsz_hint(ip));
@@ -478,8 +483,7 @@ xfs_reflink_fill_cow_hole(
 	/* Allocate the entire reservation as unwritten blocks. */
 	nimaps = 1;
 	error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
-			XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0, cmap,
-			&nimaps);
+			bmapi_flags, 0, cmap, &nimaps);
 	if (error)
 		goto out_trans_cancel;
 
-- 
2.31.1
Re: [PATCH v2 11/11] xfs: Allow block allocator to take an alignment hint
Posted by Darrick J. Wong 9 months, 3 weeks ago 
On Thu, Feb 13, 2025 at 01:56:19PM +0000, John Garry wrote:
> When issuing an atomic write by the CoW method, give the block allocator a
> hint to naturally align the data blocks.
> 
> This means that we have a better chance to issuing the atomic write via
> HW offload next time.
> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_bmap.c | 7 ++++++-
>  fs/xfs/libxfs/xfs_bmap.h | 6 +++++-
>  fs/xfs/xfs_reflink.c     | 8 ++++++--
>  3 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 0ef19f1469ec..9bfdfb7cdcae 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3454,6 +3454,12 @@ xfs_bmap_compute_alignments(
>  		align = xfs_get_cowextsz_hint(ap->ip);
>  	else if (ap->datatype & XFS_ALLOC_USERDATA)
>  		align = xfs_get_extsz_hint(ap->ip);
> +
> +	if (align > 1 && ap->flags & XFS_BMAPI_EXTSZALIGN)
> +		args->alignment = align;
> +	else
> +		args->alignment = 1;
> +
>  	if (align) {
>  		if (xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, align, 0,
>  					ap->eof, 0, ap->conv, &ap->offset,
> @@ -3782,7 +3788,6 @@ xfs_bmap_btalloc(
>  		.wasdel		= ap->wasdel,
>  		.resv		= XFS_AG_RESV_NONE,
>  		.datatype	= ap->datatype,
> -		.alignment	= 1,
>  		.minalignslop	= 0,
>  	};
>  	xfs_fileoff_t		orig_offset;
> diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
> index 4b721d935994..7a31697331dc 100644
> --- a/fs/xfs/libxfs/xfs_bmap.h
> +++ b/fs/xfs/libxfs/xfs_bmap.h
> @@ -87,6 +87,9 @@ struct xfs_bmalloca {
>  /* Do not update the rmap btree.  Used for reconstructing bmbt from rmapbt. */
>  #define XFS_BMAPI_NORMAP	(1u << 10)
>  
> +/* Try to naturally align allocations to extsz hint */
> +#define XFS_BMAPI_EXTSZALIGN	(1u << 11)

IMO "naturally" makes things confusing here -- are we aligning to the
extent size hint, or are we aligning to the length requested?  Or
whatever it is that "naturally" means.

(FWIW you and I have bumped over this repeatedly, so maybe this is
simple one of those cognitive friction things where block storage always
deals with powers of two and "naturally" means a lot, vs. filesystems
where we don't usually enforce alignment anywhere.)

I suggest "Try to align allocations to the extent size hint" for the
comment, and with that:
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> +
>  #define XFS_BMAPI_FLAGS \
>  	{ XFS_BMAPI_ENTIRE,	"ENTIRE" }, \
>  	{ XFS_BMAPI_METADATA,	"METADATA" }, \
> @@ -98,7 +101,8 @@ struct xfs_bmalloca {
>  	{ XFS_BMAPI_REMAP,	"REMAP" }, \
>  	{ XFS_BMAPI_COWFORK,	"COWFORK" }, \
>  	{ XFS_BMAPI_NODISCARD,	"NODISCARD" }, \
> -	{ XFS_BMAPI_NORMAP,	"NORMAP" }
> +	{ XFS_BMAPI_NORMAP,	"NORMAP" },\
> +	{ XFS_BMAPI_EXTSZALIGN,	"EXTSZALIGN" }
>  
>  
>  static inline int xfs_bmapi_aflag(int w)
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index d097d33dc000..033dff86ecf0 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -445,6 +445,11 @@ xfs_reflink_fill_cow_hole(
>  	int			nimaps;
>  	int			error;
>  	bool			found;
> +	uint32_t		bmapi_flags = XFS_BMAPI_COWFORK |
> +					      XFS_BMAPI_PREALLOC;
> +
> +	if (atomic)
> +		bmapi_flags |= XFS_BMAPI_EXTSZALIGN;
>  
>  	resaligned = xfs_aligned_fsb_count(imap->br_startoff,
>  		imap->br_blockcount, xfs_get_cowextsz_hint(ip));
> @@ -478,8 +483,7 @@ xfs_reflink_fill_cow_hole(
>  	/* Allocate the entire reservation as unwritten blocks. */
>  	nimaps = 1;
>  	error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
> -			XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0, cmap,
> -			&nimaps);
> +			bmapi_flags, 0, cmap, &nimaps);
>  	if (error)
>  		goto out_trans_cancel;
>  
> -- 
> 2.31.1
> 
>
Re: [PATCH v2 11/11] xfs: Allow block allocator to take an alignment hint
Posted by John Garry 9 months, 3 weeks ago 
On 24/02/2025 20:37, Darrick J. Wong wrote:
> On Thu, Feb 13, 2025 at 01:56:19PM +0000, John Garry wrote:
>> When issuing an atomic write by the CoW method, give the block allocator a
>> hint to naturally align the data blocks.
>>
>> This means that we have a better chance to issuing the atomic write via
>> HW offload next time.
>>
>> Signed-off-by: John Garry <john.g.garry@oracle.com>
>> ---
>>   fs/xfs/libxfs/xfs_bmap.c | 7 ++++++-
>>   fs/xfs/libxfs/xfs_bmap.h | 6 +++++-
>>   fs/xfs/xfs_reflink.c     | 8 ++++++--
>>   3 files changed, 17 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
>> index 0ef19f1469ec..9bfdfb7cdcae 100644
>> --- a/fs/xfs/libxfs/xfs_bmap.c
>> +++ b/fs/xfs/libxfs/xfs_bmap.c
>> @@ -3454,6 +3454,12 @@ xfs_bmap_compute_alignments(
>>   		align = xfs_get_cowextsz_hint(ap->ip);
>>   	else if (ap->datatype & XFS_ALLOC_USERDATA)
>>   		align = xfs_get_extsz_hint(ap->ip);
>> +
>> +	if (align > 1 && ap->flags & XFS_BMAPI_EXTSZALIGN)
>> +		args->alignment = align;
>> +	else
>> +		args->alignment = 1;
>> +
>>   	if (align) {
>>   		if (xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, align, 0,
>>   					ap->eof, 0, ap->conv, &ap->offset,
>> @@ -3782,7 +3788,6 @@ xfs_bmap_btalloc(
>>   		.wasdel		= ap->wasdel,
>>   		.resv		= XFS_AG_RESV_NONE,
>>   		.datatype	= ap->datatype,
>> -		.alignment	= 1,
>>   		.minalignslop	= 0,
>>   	};
>>   	xfs_fileoff_t		orig_offset;
>> diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
>> index 4b721d935994..7a31697331dc 100644
>> --- a/fs/xfs/libxfs/xfs_bmap.h
>> +++ b/fs/xfs/libxfs/xfs_bmap.h
>> @@ -87,6 +87,9 @@ struct xfs_bmalloca {
>>   /* Do not update the rmap btree.  Used for reconstructing bmbt from rmapbt. */
>>   #define XFS_BMAPI_NORMAP	(1u << 10)
>>   
>> +/* Try to naturally align allocations to extsz hint */
>> +#define XFS_BMAPI_EXTSZALIGN	(1u << 11)
> 
> IMO "naturally" makes things confusing here -- are we aligning to the
> extent size hint, or are we aligning to the length requested?  Or
> whatever it is that "naturally" means.

We align to extsz hint, not length.

As for use of word "naturally", I'll try to avoid using that word.

> 
> (FWIW you and I have bumped over this repeatedly, so maybe this is
> simple one of those cognitive friction things where block storage always
> deals with powers of two and "naturally" means a lot, vs. filesystems
> where we don't usually enforce alignment anywhere.)
> 
> I suggest "Try to align allocations to the extent size hint" for the
> comment, and with that:

that's fine

> Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
> 

cheers,
John

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