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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784737944; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bBnIrrxiyHbn5CbW2/3RvfkB4lrliRmpnHXHN4bKIgA=; b=b0Rt1yNkrfg4I8fIySJ7tAmqfRb/Rv7DlSybC9R/Cxce9tKHq48cy7/r/AoabRFRXbmLoS GTnqjiTkp4wrI86UX+LsR+yLWAl3mRARIY31Dz4xpRbhC9PecgUBRKwJScz9DmdsKW4gq/ l8Jv5MWPPRaQw8rpGnXT4vA8GhYeRgE= From: Usama Arif To: Christoph Hellwig Cc: Usama Arif , baoquan.he@linux.dev, akpm@linux-foundation.org, chrisl@kernel.org, kasong@tencent.com, nphamcs@gmail.com, shikemeng@huaweicloud.com, youngjun.park@lge.com, ryncsn@gmail.com, trondmy@kernel.org, anna@kernel.org, sfrench@samba.org, linux-mm@kvack.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH 2/3] mm/swap: add a new swap_ops.h header to allow for pluggable swap ops Date: Wed, 22 Jul 2026 09:32:17 -0700 Message-ID: <20260722163218.1240273-1-usama.arif@linux.dev> In-Reply-To: <20260722130615.3163560-3-hch@lst.de> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5583640011 X-Stat-Signature: x61z4hndmjj93t5u9a5syf3okoozby55 X-Rspam-User: X-HE-Tag: 1784737948-107137 X-HE-Meta: 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 KRgJYdUI HMnEhUb+t1uvF81Ul4LknuhYD2ixqRM+W9Reg3OIGXu7sGf/5R79nNYv0gr/2QPfruvjmxOKcoaM2qxuLCyXipue6Y1VJ7hMB1rBCNQLJxdfqH+PJnzjroIIT8fZ8sQT9CppQZLZ0g9cQuXz4y3r0S9Sg6y0OSRhG0HgLH+oFbJuE4scIJOCpG+oCFU0HCv4CH9Xlu3jq63/ECSLCr81IkGt5Uz82L4n+yIbFzEBLcXnx/u7dAe+E92t9VA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 22 Jul 2026 15:06:08 +0200 Christoph Hellwig wrote: > Add a new header to declare the swap_iocb, swap_ops and swap_ctx to > allow for swap_ops implementations outside of mm/page_io.c. This > will be used to remove the double indirection for file system-based > swap. > > Note that there already is a swapops.h header, which is totally > unrelated to struct swap_ops. The close naming is a bit unfortunate, > but I could not think of a better name for this header. > > Signed-off-by: Christoph Hellwig > --- > MAINTAINERS | 1 + > include/linux/swap_ops.h | 39 +++++++++++++++++++++++++++++++++++++++ > mm/madvise.c | 1 + > mm/page_io.c | 10 +--------- > mm/shmem.c | 1 + > mm/swap.h | 23 +---------------------- > mm/swap_state.c | 1 + > mm/vmscan.c | 1 + > 8 files changed, 46 insertions(+), 31 deletions(-) > create mode 100644 include/linux/swap_ops.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index 5da77924c6f0..cda42b7ed945 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -17240,6 +17240,7 @@ S: Maintained > F: Documentation/ABI/testing/sysfs-kernel-mm-swap > F: Documentation/mm/swap-table.rst > F: include/linux/swap.h > +F: include/linux/swap_ops.h > F: include/linux/swapfile.h > F: include/linux/swapops.h > F: mm/page_io.c > diff --git a/include/linux/swap_ops.h b/include/linux/swap_ops.h > new file mode 100644 > index 000000000000..e92b4f532604 > --- /dev/null > +++ b/include/linux/swap_ops.h > @@ -0,0 +1,39 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _MM_SWAP_OPS_H > +#define _MM_SWAP_OPS_H > + > +#include /* for SWAP_CLUSTER_MAX */ > + > +struct swap_iocb { > + union { > + struct kiocb iocb; > + struct bio bio; > + }; > + struct bio_vec bvecs[SWAP_CLUSTER_MAX]; > + int nr_bvecs; > + int len; > +}; > + > +struct swap_io_ctx { > + struct swap_iocb *sio; > + struct swap_info_struct *sis; > +}; zswap uses this struct, I think you need to include the header in zswap.c as well, good to check if the build is passing with CONFIG_ZSWAP=y > + > +/* > + * SWAP_OPS_F_REQUIRE_NOFS: > + * When set, all reclaim operations must operated as GFS_NOFS and not > + * just GFP_NOIO, as GFP_NOIO allocations could recourse into the > + * file system backing this swap file. > + */ > +#define SWAP_OPS_F_REQUIRE_NOFS (1U << 0) > + > +struct swap_ops { > + unsigned int flags; > + > + bool (*can_merge)(struct folio *folio, struct folio *prev_folio, > + size_t prev_folio_size, int rw); > + void (*submit_write)(struct swap_io_ctx *ctx); > + void (*submit_read)(struct swap_io_ctx *ctx); > +}; > + > +#endif /* _MM_SWAP_OPS_H */ > diff --git a/mm/madvise.c b/mm/madvise.c > index 07a21ca31bad..c179938097bf 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -32,6 +32,7 @@ > #include > #include > #include > +#include > > #include > > diff --git a/mm/page_io.c b/mm/page_io.c > index c984a4023a65..e741e67d6592 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -25,6 +25,7 @@ > #include > #include > #include > +#include > #include "swap.h" > #include "swap_table.h" > > @@ -300,15 +301,6 @@ static bool folio_blkg_can_merge(struct folio *folio, struct folio *prev_folio) > #define bio_associate_blkg_from_page(bio, folio) do { } while (0) > #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */ > > -struct swap_iocb { > - union { > - struct kiocb iocb; > - struct bio bio; > - }; > - struct bio_vec bvecs[SWAP_CLUSTER_MAX]; > - int nr_bvecs; > - int len; > -}; > static mempool_t *sio_pool; > > int sio_pool_init(void) > diff --git a/mm/shmem.c b/mm/shmem.c > index 5071177059a9..797c42f024a0 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -41,6 +41,7 @@ > #include > #include > #include > +#include > #include "swap.h" > > static struct vfsmount *shm_mnt __ro_after_init; > diff --git a/mm/swap.h b/mm/swap.h > index abd26588abd2..19ea61c97df2 100644 > --- a/mm/swap.h > +++ b/mm/swap.h > @@ -8,6 +8,7 @@ > struct mempolicy; > struct swap_iocb; > struct swap_memcg_table; > +struct swap_io_ctx; > > #if defined(MAX_POSSIBLE_PHYSMEM_BITS) > #define SWAP_CACHE_PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT) > @@ -77,28 +78,6 @@ enum swap_cluster_flags { > CLUSTER_FLAG_MAX, > }; > > -struct swap_io_ctx { > - struct swap_iocb *sio; > - struct swap_info_struct *sis; > -}; > - > -/* > - * SWAP_OPS_F_REQUIRE_NOFS: > - * When set, all reclaim operations must operated as GFS_NOFS and not > - * just GFP_NOIO, as GFP_NOIO allocations could recourse into the > - * file system backing this swap file. > - */ > -#define SWAP_OPS_F_REQUIRE_NOFS (1U << 0) > - > -struct swap_ops { > - unsigned int flags; > - > - bool (*can_merge)(struct folio *folio, struct folio *prev_folio, > - size_t prev_folio_size, int rw); > - void (*submit_write)(struct swap_io_ctx *ctx); > - void (*submit_read)(struct swap_io_ctx *ctx); > -}; > - > #ifdef CONFIG_SWAP > #include /* for swp_offset */ > #include /* for bio_end_io_t */ > diff --git a/mm/swap_state.c b/mm/swap_state.c > index 5be825911e64..b76eb3d876fd 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -23,6 +23,7 @@ > #include > #include > #include > +#include > #include "internal.h" > #include "swap_table.h" > #include "swap.h" > diff --git a/mm/vmscan.c b/mm/vmscan.c > index e26c6931f5fd..a12eb79c89c5 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -58,6 +58,7 @@ > #include > #include > #include > +#include > > #include > #include > -- > 2.53.0 > >