From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 177EA411F81 for ; Mon, 27 Jul 2026 13:08:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785157701; cv=none; b=WXE/3tufzCdpwL0AUxxVQKMT86p8PTI/mK6EVoU0y9Qk8+tds0Tj0qDz9teZM2AaryMPe17Ua5Tkf4PuaBncEwZ1iH9wLIAdJh0s85RCFfgtETl9qe0qflq7syE47ntejqbI9qRQc/cFwDIjU61or4RxJiRQz5zSWndmIshcn24= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785157701; c=relaxed/simple; bh=2wnQl3dDQRldsvBPML7JtFnhEAD1rjFdBRvGQQvPI30=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bGTfo477qWopJSAyBzPkuK51UPmI6wU/hI0W8Yf1+Gl5Zw8Cct8L6xw3WoEkrG3FEjAWZqwkAca/RTLLk4ZITr+mrAkFxRttSgSJ1TQ5NLIa7lk0EF5QqManflNmZT+sNvN1d7zVUmwrUr3JT9VetAjfL1HfG5F+WEGSkg/rEg0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=fzRZAVmE; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fzRZAVmE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1785157698; 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=JEjFOgu+/acrb321tynAnZZWtqfZT79BXOE4gL4kLO0=; b=fzRZAVmEFIDr/F7qMdvcWnWuMk3KgTfiNYxz6e7fYio8JuUb/N/cCmd8UBxm51QCrdNPhB uGuO338fF7I8lGY1biB54oR51W9ZQvgJS0rjXhNP1TaGPv51CL8WUgCDTJbe9AxcA1s5vs kYSHlWLgILC6fwCB9gCSBv3ILK6N9Jg= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-656-XvklwJSBPeKNTHthq13cuQ-1; Mon, 27 Jul 2026 09:08:14 -0400 X-MC-Unique: XvklwJSBPeKNTHthq13cuQ-1 X-Mimecast-MFC-AGG-ID: XvklwJSBPeKNTHthq13cuQ_1785157693 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ADB1E1801A0E; Mon, 27 Jul 2026 13:08:12 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.33.159]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E39EA30010C8; Mon, 27 Jul 2026 13:08:08 +0000 (UTC) From: David Howells To: Christian Brauner Cc: David Howells , Paulo Alcantara , Christoph Hellwig , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+0da43efa72f88bd3a8af@syzkaller.appspotmail.com, Yun Zhou , Matthew Wilcox Subject: [PATCH 4/4] netfs: Fix folio_queue ENOMEM in writeback by adding a mempool Date: Mon, 27 Jul 2026 14:07:15 +0100 Message-ID: <20260727130716.1099906-5-dhowells@redhat.com> In-Reply-To: <20260727130716.1099906-1-dhowells@redhat.com> References: <20260727130716.1099906-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-cifs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Fix the handling of folio_queue allocation failure in writeback by adding a mempool and passing in gfp_t flags to the rolling buffer functions that allocate memory, using the mempool if gfp != GFP_KERNEL. This is then extended upwards and the gfp to be used for a request is stored in the netfs_io_request struct and is then used for both requests and subrequests, eliminating the sleeping loops there. The failure caused: folio != NULL WARNING: fs/netfs/write_issue.c:603 at netfs_writepages+0x883/0xa10 fs/netfs/write_issue.c:603, CPU#3: syz.0.17/5919 Fixes: cd0277ed0c18 ("netfs: Use new folio_queue data type and iterator instead of xarray iter") Reported-by: syzbot+0da43efa72f88bd3a8af@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=0da43efa72f88bd3a8af Signed-off-by: David Howells Tested-by: syzbot+0da43efa72f88bd3a8af@syzkaller.appspotmail.com cc: Paulo Alcantara cc: Yun Zhou cc: Matthew Wilcox cc: Christoph Hellwig cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- fs/netfs/buffered_read.c | 6 +++--- fs/netfs/internal.h | 1 + fs/netfs/main.c | 7 +++++++ fs/netfs/objects.c | 31 +++++++++++++++++++------------ fs/netfs/read_pgpriv2.c | 2 +- fs/netfs/rolling_buffer.c | 21 ++++++++++++--------- fs/netfs/write_issue.c | 10 +++++----- include/linux/netfs.h | 1 + include/linux/rolling_buffer.h | 6 +++--- 9 files changed, 52 insertions(+), 33 deletions(-) diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c index 3d86414ee40f..7fdfa4f27e34 100644 --- a/fs/netfs/buffered_read.c +++ b/fs/netfs/buffered_read.c @@ -361,7 +361,7 @@ void netfs_readahead(struct readahead_control *ractl) netfs_rreq_expand(rreq, ractl); rreq->submitted = rreq->start; - if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST) < 0) + if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST, rreq->gfp) < 0) goto cleanup_free; netfs_read_to_pagecache(rreq, ractl); @@ -380,10 +380,10 @@ static int netfs_create_singular_buffer(struct netfs_io_request *rreq, struct fo { ssize_t added; - if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST) < 0) + if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST, rreq->gfp) < 0) return -ENOMEM; - added = rolling_buffer_append(&rreq->buffer, folio, rollbuf_flags); + added = rolling_buffer_append(&rreq->buffer, folio, rollbuf_flags, rreq->gfp); if (added < 0) return added; rreq->submitted = rreq->start + added; diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h index d889caa401dc..420ee7b26580 100644 --- a/fs/netfs/internal.h +++ b/fs/netfs/internal.h @@ -43,6 +43,7 @@ extern struct list_head netfs_io_requests; extern spinlock_t netfs_proc_lock; extern mempool_t netfs_request_pool; extern mempool_t netfs_subrequest_pool; +extern mempool_t netfs_folioq_pool; #ifdef CONFIG_PROC_FS static inline void netfs_proc_add_rreq(struct netfs_io_request *rreq) diff --git a/fs/netfs/main.c b/fs/netfs/main.c index 73da6c9f5777..927badf3989d 100644 --- a/fs/netfs/main.c +++ b/fs/netfs/main.c @@ -28,6 +28,7 @@ static struct kmem_cache *netfs_request_slab; static struct kmem_cache *netfs_subrequest_slab; mempool_t netfs_request_pool; mempool_t netfs_subrequest_pool; +mempool_t netfs_folioq_pool; #ifdef CONFIG_PROC_FS LIST_HEAD(netfs_io_requests); @@ -108,6 +109,9 @@ static int __init netfs_init(void) { int ret = -ENOMEM; + if (mempool_init_kmalloc_pool(&netfs_folioq_pool, 100, sizeof(struct folio_queue)) < 0) + goto error_folioq_pool; + netfs_request_slab = kmem_cache_create("netfs_request", sizeof(struct netfs_io_request), 0, SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, @@ -160,6 +164,8 @@ static int __init netfs_init(void) error_reqpool: kmem_cache_destroy(netfs_request_slab); error_req: + mempool_exit(&netfs_folioq_pool); +error_folioq_pool: return ret; } fs_initcall(netfs_init); @@ -172,5 +178,6 @@ static void __exit netfs_exit(void) kmem_cache_destroy(netfs_subrequest_slab); mempool_exit(&netfs_request_pool); kmem_cache_destroy(netfs_request_slab); + mempool_exit(&netfs_folioq_pool); } module_exit(netfs_exit); diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c index b8c4918d3dcd..29d8eab06dec 100644 --- a/fs/netfs/objects.c +++ b/fs/netfs/objects.c @@ -7,7 +7,6 @@ #include #include -#include #include "internal.h" static void netfs_free_request(struct work_struct *work); @@ -26,17 +25,23 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping, struct netfs_io_request *rreq; mempool_t *mempool = ctx->ops->request_pool ?: &netfs_request_pool; struct kmem_cache *cache = mempool->pool_data; + gfp_t gfp = GFP_KERNEL; int ret; - for (;;) { - rreq = mempool_alloc(mempool, GFP_KERNEL); - if (rreq) - break; - msleep(10); + /* Writeback is part of memory reclaim and must not fail due to ENOMEM. */ + if (origin == NETFS_WRITEBACK || origin == NETFS_WRITEBACK_SINGLE) { + gfp = GFP_NOFS; /* Allows use of mempools. */ + + rreq = mempool_alloc(mempool, gfp); + } else { + rreq = mempool->alloc(gfp, mempool->pool_data); + if (!rreq) + return ERR_PTR(-ENOMEM); } memset(rreq, 0, kmem_cache_size(cache)); INIT_WORK(&rreq->cleanup_work, netfs_free_request); + rreq->gfp = gfp; rreq->start = start; rreq->len = len; rreq->origin = origin; @@ -200,12 +205,14 @@ struct netfs_io_subrequest *netfs_alloc_subrequest(struct netfs_io_request *rreq mempool_t *mempool = rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool; struct kmem_cache *cache = mempool->pool_data; - for (;;) { - subreq = mempool_alloc(rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool, - GFP_KERNEL); - if (subreq) - break; - msleep(10); + if (rreq->gfp == GFP_KERNEL) { + subreq = mempool->alloc(rreq->gfp, mempool->pool_data); + if (!subreq) + return ERR_PTR(-ENOMEM); + } else { + subreq = mempool_alloc(mempool, rreq->gfp); + if (!subreq) + return NULL; } memset(subreq, 0, kmem_cache_size(cache)); diff --git a/fs/netfs/read_pgpriv2.c b/fs/netfs/read_pgpriv2.c index 7eacc58abadb..c31190993b76 100644 --- a/fs/netfs/read_pgpriv2.c +++ b/fs/netfs/read_pgpriv2.c @@ -53,7 +53,7 @@ static void netfs_pgpriv2_copy_folio(struct netfs_io_request *creq, struct folio trace_netfs_folio(folio, netfs_folio_trace_store_copy); /* Attach the folio to the rolling buffer. */ - if (rolling_buffer_append(&creq->buffer, folio, 0) < 0) { + if (rolling_buffer_append(&creq->buffer, folio, 0, creq->gfp) < 0) { folio_end_private_2(folio); clear_bit(NETFS_RREQ_FOLIO_COPY_TO_CACHE, &creq->flags); return; diff --git a/fs/netfs/rolling_buffer.c b/fs/netfs/rolling_buffer.c index a17fbf9853a4..c7f107764bda 100644 --- a/fs/netfs/rolling_buffer.c +++ b/fs/netfs/rolling_buffer.c @@ -27,7 +27,10 @@ struct folio_queue *netfs_folioq_alloc(unsigned int rreq_id, gfp_t gfp, { struct folio_queue *fq; - fq = kmalloc_obj(*fq, gfp); + if (gfp == GFP_KERNEL) + fq = netfs_folioq_pool.alloc(gfp, netfs_folioq_pool.pool_data); + else + fq = mempool_alloc(&netfs_folioq_pool, gfp); if (fq) { netfs_stat(&netfs_n_folioq); folioq_init(fq, rreq_id); @@ -50,7 +53,7 @@ void netfs_folioq_free(struct folio_queue *folioq, { trace_netfs_folioq(folioq, trace); netfs_stat_d(&netfs_n_folioq); - kfree(folioq); + mempool_free(folioq, &netfs_folioq_pool); } EXPORT_SYMBOL(netfs_folioq_free); @@ -60,11 +63,11 @@ EXPORT_SYMBOL(netfs_folioq_free); * consumer. */ int rolling_buffer_init(struct rolling_buffer *roll, unsigned int rreq_id, - unsigned int direction) + unsigned int direction, gfp_t gfp) { struct folio_queue *fq; - fq = netfs_folioq_alloc(rreq_id, GFP_NOFS, netfs_trace_folioq_rollbuf_init); + fq = netfs_folioq_alloc(rreq_id, gfp, netfs_trace_folioq_rollbuf_init); if (!fq) return -ENOMEM; @@ -77,14 +80,14 @@ int rolling_buffer_init(struct rolling_buffer *roll, unsigned int rreq_id, /* * Add another folio_queue to a rolling buffer if there's no space left. */ -int rolling_buffer_make_space(struct rolling_buffer *roll) +int rolling_buffer_make_space(struct rolling_buffer *roll, gfp_t gfp) { struct folio_queue *fq, *head = roll->head; if (!folioq_full(head)) return 0; - fq = netfs_folioq_alloc(head->rreq_id, GFP_NOFS, netfs_trace_folioq_make_space); + fq = netfs_folioq_alloc(head->rreq_id, gfp, netfs_trace_folioq_make_space); if (!fq) return -ENOMEM; fq->prev = head; @@ -122,7 +125,7 @@ ssize_t rolling_buffer_load_from_ra(struct rolling_buffer *roll, int nr, ix, to; ssize_t size = 0; - if (rolling_buffer_make_space(roll) < 0) + if (rolling_buffer_make_space(roll, GFP_KERNEL) < 0) return -ENOMEM; fq = roll->head; @@ -153,12 +156,12 @@ ssize_t rolling_buffer_load_from_ra(struct rolling_buffer *roll, * Append a folio to the rolling buffer. */ ssize_t rolling_buffer_append(struct rolling_buffer *roll, struct folio *folio, - unsigned int flags) + unsigned int flags, gfp_t gfp) { ssize_t size = folio_size(folio); int slot; - if (rolling_buffer_make_space(roll) < 0) + if (rolling_buffer_make_space(roll, gfp) < 0) return -ENOMEM; slot = folioq_append(roll->head, folio); diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c index 14efe4cb9393..2d9cfcd43658 100644 --- a/fs/netfs/write_issue.c +++ b/fs/netfs/write_issue.c @@ -108,7 +108,7 @@ struct netfs_io_request *netfs_create_write_req(struct address_space *mapping, ictx = netfs_inode(wreq->inode); if (is_cacheable) fscache_begin_write_operation(&wreq->cache_resources, netfs_i_cookie(ictx)); - if (rolling_buffer_init(&wreq->buffer, wreq->debug_id, ITER_SOURCE) < 0) + if (rolling_buffer_init(&wreq->buffer, wreq->debug_id, ITER_SOURCE, wreq->gfp) < 0) goto nomem; wreq->cleaned_to = wreq->start; @@ -167,7 +167,7 @@ void netfs_prepare_write(struct netfs_io_request *wreq, */ if (iov_iter_is_folioq(wreq_iter) && wreq_iter->folioq_slot >= folioq_nr_slots(wreq_iter->folioq)) - rolling_buffer_make_space(&wreq->buffer); + rolling_buffer_make_space(&wreq->buffer, wreq->gfp); subreq = netfs_alloc_subrequest(wreq); subreq->source = stream->source; @@ -334,7 +334,7 @@ static int netfs_write_folio(struct netfs_io_request *wreq, _enter(""); - if (rolling_buffer_make_space(&wreq->buffer) < 0) + if (rolling_buffer_make_space(&wreq->buffer, wreq->gfp) < 0) return -ENOMEM; /* netfs_perform_write() may shift i_size around the page or from out @@ -436,7 +436,7 @@ static int netfs_write_folio(struct netfs_io_request *wreq, } /* Attach the folio to the rolling buffer. */ - rolling_buffer_append(&wreq->buffer, folio, 0); + rolling_buffer_append(&wreq->buffer, folio, 0, wreq->gfp); /* Move the submission point forward to allow for write-streaming data * not starting at the front of the page. We don't do write-streaming @@ -749,7 +749,7 @@ static int netfs_write_folio_single(struct netfs_io_request *wreq, /* Attach the folio to the rolling buffer. */ folio_get(folio); - ret = rolling_buffer_append(&wreq->buffer, folio, NETFS_ROLLBUF_PUT_MARK); + ret = rolling_buffer_append(&wreq->buffer, folio, NETFS_ROLLBUF_PUT_MARK, wreq->gfp); if (ret < 0) { folio_put(folio); return ret; diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 1bc120d61c5b..d0b62d53eea9 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -255,6 +255,7 @@ 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 */ const struct folio *no_unlock_folio; /* Don't unlock this folio after read */ + gfp_t gfp; /* GFP flags to use */ unsigned int direct_bv_count; /* Number of elements in direct_bv[] */ unsigned int debug_id; unsigned int rsize; /* Maximum read size (0 for none) */ diff --git a/include/linux/rolling_buffer.h b/include/linux/rolling_buffer.h index ac15b1ffdd83..9e5dad29669c 100644 --- a/include/linux/rolling_buffer.h +++ b/include/linux/rolling_buffer.h @@ -43,13 +43,13 @@ struct rolling_buffer_snapshot { #define ROLLBUF_MARK_2 BIT(1) int rolling_buffer_init(struct rolling_buffer *roll, unsigned int rreq_id, - unsigned int direction); -int rolling_buffer_make_space(struct rolling_buffer *roll); + unsigned int direction, gfp_t gfp); +int rolling_buffer_make_space(struct rolling_buffer *roll, gfp_t gfp); ssize_t rolling_buffer_load_from_ra(struct rolling_buffer *roll, struct readahead_control *ractl, struct folio_batch *put_batch); ssize_t rolling_buffer_append(struct rolling_buffer *roll, struct folio *folio, - unsigned int flags); + unsigned int flags, gfp_t gfp); struct folio_queue *rolling_buffer_delete_spent(struct rolling_buffer *roll); void rolling_buffer_clear(struct rolling_buffer *roll);