From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.128.177 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792562618; b=kGGBdtdmX2l0qXfd7QocCs1flShDIOxplR3swYKovHTysHDCtBnqh/TmO7hJJObr4Hsu b50U9tpfbgNoGm4CPlQ2CVSopH6vmlFwm/BBLQAAQaxRsWeMswOuMX7FFROr+YROVYIkY Iaa83krdpxL1YnjgCuTy9k9bKtqpYKNILLQnDxj3SnU5R0uzi552c482mIWpviiS/i8zp ZYaCfeqRCSH/uXPIhXmr4tb5AzPFYoqtpsUuVMknwm9QqIdS4g4Avc7N4x0deBt2ozVn7 N8VJkOetx/8s0HYW9be0i3/JaH2I+JfWxjHa5eCK+nSYsuZpYuVyryC7LmmkMKXKuvQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792562618; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: From:To:Cc:Subject:Date:Message-ID:X-Mailer:In-Reply-To:References: MIME-Version:Content-Transfer-Encoding; bh=dNeuvlXkDtmzEanbiS7+cKjYAzmaJIW02TKw/krsK3M=; b=4S0b5KfthB4LPK5whs669kpgrb0SBNdba8XIBmIv/6nO5w8Ac2vl61zNUWJMWDOIV4u4 h1xufH8oDH6qmn7uwkrOOuV8pndBUdLl97R869ErD0cgclcMDr53DySqXH0nRF0stS2M1 TnTejLuZWsnUIzrqSO2c/BRctWG/Q7D4C6QhAanjlC3v2BXBoGTp3/Cqqa/3oQMND+LL+ 8YWNsIfJNStyjYXGMJAReXV3KmqN+YtPwVFyD46ZVjmsTX9NhRBP8ESQjJS2VhxSEq72D hCIJqDqZvMlWUJ8M15iqN4vXD2Ga8J6QAEGA9oVlFWAiefbY1t7iJWlHn7ADs8Jricw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20251104 header.b=pkLYeSmp; arc=none smtp.remote-ip=209.85.128.177 Received: from mail-yw1-f177.google.com (mail-yw1-f177.google.com [209.85.128.177]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A67F460A2613 for ; Wed, 21 Oct 2026 06:03:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org A67F460A2613 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20251104 header.b=pkLYeSmp Received: by mail-yw1-f177.google.com with SMTP id 00721157ae682-8ab3d3c5761so3117197b3.1 for ; Tue, 20 Oct 2026 23:03:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1792562617; x=1793167417; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=dNeuvlXkDtmzEanbiS7+cKjYAzmaJIW02TKw/krsK3M=; b=pkLYeSmp3K2heI9H91i1L6VD/mLumW6KSD6pL5WdXGB7/XZ3n0SnjIOxChNrMsiShs 0CjATZ59H1UEL79o2Pov02Yu02TiIG/8vAZoIK0IF/fsAAia6QvEDHtcOsqMIpI64Woq psFmDJa3PqlycRJCjt29dsEqZn0tzEROycw4FVjwIvGYIZAohGQR8T/uNcydGTByGSJn Yowj1QMSoblTu54CEB53MP191kjIeO+vhx7Un+SM3xtFrVCdydwO257cIM/l08pE8CCX THu0UwkZJ7WpY9+AjBEFtw9ISXS/fN8dkQ4hv+TqdrF0Deh2nESf/n8hdc+jk2NJYPOK YjKQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792562617; x=1793167417; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=dNeuvlXkDtmzEanbiS7+cKjYAzmaJIW02TKw/krsK3M=; b=knkpMHAPxTI2V01ObB9wsKsU66xGZM1EkziU7V16uBtHvDIEx93aBmSuT9CBLjRR1b fnOK8ED7L7SfuLajjNbfafIs4GAM6vmgkphoxxYILuHuyFTBRI9qoLFLMLYoLFIvKVmx n+YYzNy4QFKMStkFRtBF7n/QFs/PpUPnRO9Vt/22sg+/osoYGmcycViOcmeXrbcsq7qF KlRahWfgqQFSqTdZ/MYmYX9z5qEauWjNGhVa5IT+CwabswLwy/PSuk4zF33mOWSckc73 Vv+bphSxeAVaBAq8CprJIgnG/2isJY8UFFRxQ93WjqMIKJsjgskbwn92RERS8sUnV9xo nokA== X-Forwarded-Encrypted: i=1; AKwUvBzmsRQcTgxMEP+MzRpqGpnaH5IUQngDMmjE5q94rwxpSGMuJEesbUOn7PwOQsrp1dTOTJ8B4fam@vger.kernel.org X-Gm-Message-State: AFq9FYLkRizyWqBPn/7Pc5OEYM2cP/SXuz2Z90uvz/WMRbJbuLArqZbV lBE0scuqKvcsNW/Yv9ISL5DCyb19olMY5wxbft0hQrqjGg6XKxgP5T1n X-Gm-Gg: AYBFou1V6S/2tprEpsJx948x4euhXI0uRM5bCeYIbjSzvaaEtlJa3XwwTfy8HvbS2+e 0KvDJxQTUaDg7B0/LjcR3YbKdSij+RtAdFD1yPs9za70VnQDVvj65JSd8iYDLrXk3IijOHxyTpd zWeBowbihXtVsEZ0nAI1BATByv66b6iF4w9P70oops44MOozNOrI3sRLgusIuULMySawjdVb6ya gnxZz4zj654k76XwiEkHHl4fUvjqMxp/K0Ki6hzRfPK7H3t85YMgJm92vGnoRsMuOcH6yJMrsRQ 4vnKHlK2BkL3aukA+hAq2m5P8nbnXzwhMJsXAFWf0xk5jzROzLCrubdSNuUtOuOmQFp3aEUDlx1 tQ2+yVVxyOjWukwrpP8Mh2hclL4bpmpfMt59TVZ3Fbzp1IbK22S0egTufsD8ShWSfx4YQQIQO5t Ci0KgN3SvgvdQpQoyJhPUIWGB5easiHTDXU3Ah52udKQx0GbwYCxEKTExKdx8q+uTuLZcXBQ7ys M3Aa/oXpFTBaEDGgDYhOX8x6P1IMAtNft9Z+J3czuTnwK/I6DyLedMP7XHOFhEtB9vl/fifFxgq x5W7gy5ChhjebjY/skzwShXFarjGe3oWh0AklshqW1Np+WWtCp+ZeWw68RqCHxxO X-Received: by 2002:a05:690c:e3c3:b0:8af:1843:a9e5 with SMTP id 00721157ae682-8b133d0636bmr5788747b3.23.1792562616594; Tue, 20 Oct 2026 23:03:36 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:42::]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8b1300c85c9sm7295167b3.23.2026.10.20.23.03.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Oct 2026 23:03:34 -0700 (PDT) From: Nhat Pham To: akpm@linux-foundation.org Cc: chrisl@kernel.org, kasong@tencent.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, yosry@kernel.org, david@kernel.org, muchun.song@linux.dev, shikemeng@huaweicloud.com, baoquan.he@linux.dev, baohua@kernel.org, youngjun.park@lge.com, chengming.zhou@linux.dev, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, qi.zheng@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, riel@surriel.com, gourry@gourry.net, haowenchao22@gmail.com, corbet@lwn.net, hughd@google.com, baolin.wang@linux.alibaba.com, tj@kernel.org, mkoutny@suse.com, skhan@linuxfoundation.org, rdunlap@infradead.org, kunwu.chan@linux.dev, kernel-team@meta.com, nphamcs@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, cgroups@vger.kernel.org Subject: [PATCH v6 03/12] mm, swap: prepare the swap IO path for vswap Date: Tue, 20 Oct 2026 23:03:14 -0700 Message-ID: <20261021060323.553433-4-nphamcs@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261021060323.553433-1-nphamcs@gmail.com> References: <20261021060323.553433-1-nphamcs@gmail.com> X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In preparation for adding a physical swap backend for vswap, make the swap IO path able to submit IO for a swap entry other than folio->swap. The swap IO path derives the target device and sector from folio->swap. For a vswap folio backed by a physical slot that entry is virtual, so it identifies neither the backing device nor the sector to submit IO against. Compute the sector from an explicit entry (swap_folio_sector becomes swap_entry_sector), thread that entry through swap_add_folio, __swap_writeout and ops->can_merge, and stash it in swap_iocb so the submit and completion paths address the IO from it rather than from folio->swap. Carry reclaim's NOFS restriction in the I/O context. A subsequent patch uses it when zswap_store() fails and writeout falls back to physical swap. ops->can_merge changes anchor with it: swap_bdev_can_merge() compares sectors and swap_fs_can_merge() byte offsets, and both now measure from the batch head plus the accumulated length instead of from the previous folio plus its size. The two agree at every step, since a batch only grows through merges that passed the same test. The blkg comparison is unchanged and still anchors on the last folio in the batch. All callers pass folio->swap, so there is no functional change. Signed-off-by: Nhat Pham --- include/linux/swap.h | 2 +- include/linux/swap_ops.h | 10 +++++--- mm/page_io.c | 54 +++++++++++++++++++--------------------- mm/swap.h | 3 ++- mm/swapfile.c | 6 ++--- mm/vmscan.c | 4 ++- mm/zswap.c | 2 +- 7 files changed, 42 insertions(+), 39 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 1479914d545d..4066d99f896e 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -414,7 +414,7 @@ extern int __swap_count(swp_entry_t entry); extern bool swap_entry_swapped(struct swap_info_struct *si, swp_entry_t entry); extern int swp_swapcount(swp_entry_t entry); extern struct swap_info_struct *get_swap_device(swp_entry_t entry); -sector_t swap_folio_sector(struct folio *folio); +sector_t swap_entry_sector(swp_entry_t entry); /* * If there is an existing swap slot reference (swap entry) and the caller diff --git a/include/linux/swap_ops.h b/include/linux/swap_ops.h index 57ac6c703f68..1c65e346e127 100644 --- a/include/linux/swap_ops.h +++ b/include/linux/swap_ops.h @@ -12,11 +12,13 @@ struct swap_iocb { struct bio_vec bvecs[SWAP_CLUSTER_MAX]; int nr_bvecs; int len; + swp_entry_t entry; /* first slot in the batch; addresses the IO */ }; struct swap_io_ctx { struct swap_iocb *sio; struct swap_info_struct *sis; + bool nofs; }; /* @@ -30,15 +32,15 @@ struct swap_io_ctx { struct swap_ops { unsigned int flags; - bool (*can_merge)(struct folio *folio, struct folio *prev_folio, - size_t prev_folio_size, int rw); + bool (*can_merge)(struct folio *folio, swp_entry_t phys, + struct swap_iocb *sio, int rw); void (*submit_write)(struct swap_io_ctx *ctx); void (*submit_read)(struct swap_io_ctx *ctx); }; void swap_fs_prepare_rw(struct swap_io_ctx *ctx, int rw, struct iov_iter *iter); -bool swap_fs_can_merge(struct folio *folio, struct folio *prev_folio, - size_t prev_folio_size, int rw); +bool swap_fs_can_merge(struct folio *folio, swp_entry_t phys, + struct swap_iocb *sio, int rw); int swap_fs_activate(struct swap_info_struct *sis, const struct swap_ops *ops); #endif /* _MM_SWAP_OPS_H */ diff --git a/mm/page_io.c b/mm/page_io.c index f849c285ba22..61bb5c6e9759 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -263,7 +263,7 @@ int swap_writeout(struct swap_io_ctx *ctx, struct folio *folio) return AOP_WRITEPAGE_ACTIVATE; } - __swap_writeout(ctx, folio); + __swap_writeout(ctx, folio, folio->swap); return 0; out_unlock: folio_unlock(folio); @@ -338,24 +338,22 @@ int sio_pool_init(void) } static bool swap_can_merge(struct swap_io_ctx *ctx, struct folio *folio, - int rw) + swp_entry_t phys, int rw) { - struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); - struct bio_vec *last_bv = &ctx->sio->bvecs[ctx->sio->nr_bvecs - 1]; - struct folio *prev_folio = bvec_folio(last_bv); - size_t prev_folio_size = folio_size(prev_folio); + struct swap_info_struct *sis = __swap_entry_to_info(phys); if (ctx->sis != sis) return false; - return sis->ops->can_merge(folio, prev_folio, prev_folio_size, rw); + return sis->ops->can_merge(folio, phys, ctx->sio, rw); } -static void swap_add_folio(struct swap_io_ctx *ctx, struct folio *folio, int rw) +static void swap_add_folio(struct swap_io_ctx *ctx, struct folio *folio, + swp_entry_t phys, int rw) { - struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); + struct swap_info_struct *sis = __swap_entry_to_info(phys); struct swap_iocb *sio = ctx->sio; - if (sio && !swap_can_merge(ctx, folio, rw)) { + if (sio && !swap_can_merge(ctx, folio, phys, rw)) { if (rw == WRITE) swap_write_submit(ctx); else @@ -368,6 +366,7 @@ static void swap_add_folio(struct swap_io_ctx *ctx, struct folio *folio, int rw) ctx->sio = sio = mempool_alloc(sio_pool, GFP_NOIO); sio->nr_bvecs = 0; sio->len = 0; + sio->entry = phys; } bvec_set_folio(&sio->bvecs[sio->nr_bvecs], folio, folio_size(folio), 0); sio->len += folio_size(folio); @@ -388,7 +387,8 @@ static void swap_add_folio(struct swap_io_ctx *ctx, struct folio *folio, int rw) } } -void __swap_writeout(struct swap_io_ctx *ctx, struct folio *folio) +void __swap_writeout(struct swap_io_ctx *ctx, struct folio *folio, + swp_entry_t phys) { VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio); @@ -404,7 +404,7 @@ void __swap_writeout(struct swap_io_ctx *ctx, struct folio *folio) folio_start_writeback(folio); folio_unlock(folio); - swap_add_folio(ctx, folio, WRITE); + swap_add_folio(ctx, folio, phys, WRITE); } /* @@ -508,7 +508,7 @@ void swap_read_folio(struct swap_io_ctx *ctx, struct folio *folio) /* We have to read from slower devices. Increase zswap protection. */ zswap_folio_swapin(folio); - swap_add_folio(ctx, folio, READ); + swap_add_folio(ctx, folio, folio->swap, READ); finish: if (workingset) { @@ -540,8 +540,6 @@ static void swap_fs_write_complete(struct kiocb *iocb, long ret) bool failed = ret != sio->len; if (failed) { - struct folio *folio = bvec_folio(&sio->bvecs[0]); - /* * In the case of swap-over-nfs, this can be a temporary failure * if the system has limited memory for allocating transmit @@ -549,7 +547,7 @@ static void swap_fs_write_complete(struct kiocb *iocb, long ret) * folio_rotate_reclaimable but rate-limit the messages. */ pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n", - ret, swap_dev_pos(folio->swap)); + ret, swap_dev_pos(sio->entry)); } swap_write_end(sio, failed); @@ -621,7 +619,7 @@ static void swap_bdev_submit_write(struct swap_io_ctx *ctx) bio_init(bio, ctx->sis->bdev, sio->bvecs, ARRAY_SIZE(sio->bvecs), REQ_OP_WRITE | REQ_SWAP); bio->bi_iter.bi_size = sio->len; - bio->bi_iter.bi_sector = swap_folio_sector(bio_first_folio_all(bio)); + bio->bi_iter.bi_sector = swap_entry_sector(sio->entry); bio_associate_blkg_from_folio(bio, bio_first_folio_all(bio)); if (ctx->sis->flags & SWP_SYNCHRONOUS_IO) { @@ -650,7 +648,7 @@ static void swap_bdev_submit_read(struct swap_io_ctx *ctx) bio_init(bio, ctx->sis->bdev, sio->bvecs, ARRAY_SIZE(sio->bvecs), REQ_OP_READ); bio->bi_iter.bi_size = sio->len; - bio->bi_iter.bi_sector = swap_folio_sector(bio_first_folio_all(bio)); + bio->bi_iter.bi_sector = swap_entry_sector(sio->entry); if (ctx->sis->flags & SWP_SYNCHRONOUS_IO) { /* @@ -668,13 +666,14 @@ static void swap_bdev_submit_read(struct swap_io_ctx *ctx) } } -static bool swap_bdev_can_merge(struct folio *folio, struct folio *prev_folio, - size_t prev_folio_size, int rw) +static bool swap_bdev_can_merge(struct folio *folio, swp_entry_t phys, + struct swap_iocb *sio, int rw) { - if (swap_folio_sector(folio) != - swap_folio_sector(prev_folio) + (prev_folio_size >> SECTOR_SHIFT)) + if (swap_entry_sector(phys) != + swap_entry_sector(sio->entry) + (sio->len >> SECTOR_SHIFT)) return false; - if (rw == WRITE && !folio_blkg_can_merge(folio, prev_folio)) + if (rw == WRITE && !folio_blkg_can_merge(folio, + bvec_folio(&sio->bvecs[sio->nr_bvecs - 1]))) return false; return true; } @@ -690,7 +689,7 @@ void swap_fs_prepare_rw(struct swap_io_ctx *ctx, int rw, struct iov_iter *iter) struct swap_iocb *sio = ctx->sio; init_sync_kiocb(&sio->iocb, ctx->sis->swap_file); - sio->iocb.ki_pos = swap_dev_pos(bvec_folio(&sio->bvecs[0])->swap); + sio->iocb.ki_pos = swap_dev_pos(sio->entry); if (rw == WRITE) sio->iocb.ki_complete = swap_fs_write_complete; else @@ -701,11 +700,10 @@ void swap_fs_prepare_rw(struct swap_io_ctx *ctx, int rw, struct iov_iter *iter) } EXPORT_SYMBOL_GPL(swap_fs_prepare_rw); -bool swap_fs_can_merge(struct folio *folio, struct folio *prev_folio, - size_t prev_folio_size, int rw) +bool swap_fs_can_merge(struct folio *folio, swp_entry_t phys, + struct swap_iocb *sio, int rw) { - return swap_dev_pos(folio->swap) == - swap_dev_pos(prev_folio->swap) + prev_folio_size; + return swap_dev_pos(phys) == swap_dev_pos(sio->entry) + sio->len; } EXPORT_SYMBOL_GPL(swap_fs_can_merge); diff --git a/mm/swap.h b/mm/swap.h index d0e7c991a4c0..b0a092b47fce 100644 --- a/mm/swap.h +++ b/mm/swap.h @@ -320,7 +320,8 @@ void swap_read_folio(struct swap_io_ctx *ctx, struct folio *folio); void swap_read_submit(struct swap_io_ctx *ctx); void swap_write_submit(struct swap_io_ctx *ctx); int swap_writeout(struct swap_io_ctx *ctx, struct folio *folio); -void __swap_writeout(struct swap_io_ctx *ctx, struct folio *folio); +void __swap_writeout(struct swap_io_ctx *ctx, struct folio *folio, + swp_entry_t phys); /* linux/mm/swap_state.c */ extern struct address_space swap_space __read_mostly; diff --git a/mm/swapfile.c b/mm/swapfile.c index 81ac45b4856e..69fac2d905a4 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -341,14 +341,14 @@ offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset) BUG(); } -sector_t swap_folio_sector(struct folio *folio) +sector_t swap_entry_sector(swp_entry_t entry) { - struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); + struct swap_info_struct *sis = __swap_entry_to_info(entry); struct swap_extent *se; sector_t sector; pgoff_t offset; - offset = swp_offset(folio->swap); + offset = swp_offset(entry); se = offset_to_swap_extent(sis, offset); sector = se->start_block + (offset - se->start_page); return sector << (PAGE_SHIFT - 9); diff --git a/mm/vmscan.c b/mm/vmscan.c index 4c5f0f97c1c7..b9c5e92757f3 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1172,7 +1172,9 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, unsigned int nr_reclaimed = 0, nr_demoted = 0; unsigned int pgactivate = 0; bool do_demote_pass; - struct swap_io_ctx ctx = {}; + struct swap_io_ctx ctx = { + .nofs = !(sc->gfp_mask & __GFP_FS), + }; folio_batch_init(&free_folios); memset(stat, 0, sizeof(*stat)); diff --git a/mm/zswap.c b/mm/zswap.c index 1ba191cbc26f..73c6b82aa593 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1159,7 +1159,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry, folio_put(folio); /* start writeback */ - __swap_writeout(&ctx, folio); + __swap_writeout(&ctx, folio, folio->swap); swap_write_submit(&ctx); return 0; -- 2.53.0-Meta