linux-kernel - [PATCH 06/11] fs/netfs: reorder struct fields to eliminate holes

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Message-ID: <20250519134813.2975312-7-dhowells@redhat.com>
Date: Mon, 19 May 2025 14:48:02 +0100
From: David Howells <dhowells@...hat.com>
To: Christian Brauner <christian@...uner.io>
Cc: David Howells <dhowells@...hat.com>,
	Paulo Alcantara <pc@...guebit.com>,
	Max Kellermann <max.kellermann@...os.com>,
	netfs@...ts.linux.dev,
	linux-afs@...ts.infradead.org,
	linux-cifs@...r.kernel.org,
	linux-nfs@...r.kernel.org,
	ceph-devel@...r.kernel.org,
	v9fs@...ts.linux.dev,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 06/11] fs/netfs: reorder struct fields to eliminate holes

From: Max Kellermann <max.kellermann@...os.com>

This shrinks `struct netfs_io_stream` from 104 to 96 bytes and `struct
netfs_io_request` from 600 to 576 bytes.

[DH: Modified as the patch to turn netfs_io_request::error into a short
was removed from the set]

Signed-off-by: Max Kellermann <max.kellermann@...os.com>
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Paulo Alcantara <pc@...guebit.com>
cc: netfs@...ts.linux.dev
cc: linux-fsdevel@...r.kernel.org
---
 include/linux/netfs.h | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 73537dafa224..33f145f7f2c2 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -144,8 +144,8 @@ struct netfs_io_stream {
 	struct netfs_io_subrequest *front;	/* Op being collected */
 	unsigned long long	collected_to;	/* Position we've collected results to */
 	size_t			transferred;	/* The amount transferred from this stream */
-	enum netfs_io_source	source;		/* Where to read from/write to */
 	unsigned short		error;		/* Aggregate error for the stream */
+	enum netfs_io_source	source;		/* Where to read from/write to */
 	unsigned char		stream_nr;	/* Index of stream in parent table */
 	bool			avail;		/* T if stream is available */
 	bool			active;		/* T if stream is active */
@@ -240,19 +240,10 @@ struct netfs_io_request {
 	void			*netfs_priv;	/* Private data for the netfs */
 	void			*netfs_priv2;	/* Private data for the netfs */
 	struct bio_vec		*direct_bv;	/* DIO buffer list (when handling iovec-iter) */
-	unsigned int		direct_bv_count; /* Number of elements in direct_bv[] */
-	unsigned int		debug_id;
-	unsigned int		rsize;		/* Maximum read size (0 for none) */
-	unsigned int		wsize;		/* Maximum write size (0 for none) */
-	atomic_t		subreq_counter;	/* Next subreq->debug_index */
-	unsigned int		nr_group_rel;	/* Number of refs to release on ->group */
-	spinlock_t		lock;		/* Lock for queuing subreqs */
 	unsigned long long	submitted;	/* Amount submitted for I/O so far */
 	unsigned long long	len;		/* Length of the request */
 	size_t			transferred;	/* Amount to be indicated as transferred */
 	long			error;		/* 0 or error that occurred */
-	enum netfs_io_origin	origin;		/* Origin of the request */
-	bool			direct_bv_unpin; /* T if direct_bv[] must be unpinned */
 	unsigned long long	i_size;		/* Size of the file */
 	unsigned long long	start;		/* Start position */
 	atomic64_t		issued_to;	/* Write issuer folio cursor */
@@ -260,7 +251,16 @@ struct netfs_io_request {
 	unsigned long long	cleaned_to;	/* Position we've cleaned folios to */
 	unsigned long long	abandon_to;	/* Position to abandon folios to */
 	pgoff_t			no_unlock_folio; /* Don't unlock this folio after read */
+	unsigned int		direct_bv_count; /* Number of elements in direct_bv[] */
+	unsigned int		debug_id;
+	unsigned int		rsize;		/* Maximum read size (0 for none) */
+	unsigned int		wsize;		/* Maximum write size (0 for none) */
+	atomic_t		subreq_counter;	/* Next subreq->debug_index */
+	unsigned int		nr_group_rel;	/* Number of refs to release on ->group */
+	spinlock_t		lock;		/* Lock for queuing subreqs */
 	unsigned char		front_folio_order; /* Order (size) of front folio */
+	enum netfs_io_origin	origin;		/* Origin of the request */
+	bool			direct_bv_unpin; /* T if direct_bv[] must be unpinned */
 	refcount_t		ref;
 	unsigned long		flags;
 #define NETFS_RREQ_OFFLOAD_COLLECTION	0	/* Offload collection to workqueue */