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Tue, 21 Oct 2025 12:05:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id aEsqGRF392hgYgAAD6G6ig (envelope-from ); Tue, 21 Oct 2025 12:05:37 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 25CF4A0990; Tue, 21 Oct 2025 14:05:33 +0200 (CEST) Date: Tue, 21 Oct 2025 14:05:33 +0200 From: Jan Kara To: Kundan Kumar Cc: jaegeuk@kernel.org, chao@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, miklos@szeredi.hu, agruenba@redhat.com, trondmy@kernel.org, anna@kernel.org, akpm@linux-foundation.org, willy@infradead.org, mcgrof@kernel.org, clm@meta.com, david@fromorbit.com, amir73il@gmail.com, axboe@kernel.dk, hch@lst.de, ritesh.list@gmail.com, djwong@kernel.org, dave@stgolabs.net, wangyufei@vivo.com, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, gfs2@lists.linux.dev, linux-nfs@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, anuj20.g@samsung.com, vishak.g@samsung.com, joshi.k@samsung.com Subject: Re: [PATCH v2 05/16] writeback: modify bdi_writeback search logic to search across all wb ctxs Message-ID: <64svwwe2zosyjibtzmhxj4fvffhzlmntrf2fsxlh7jhj33c5wl@h3vqsl74fihv> References: <20251014120845.2361-1-kundan.kumar@samsung.com> <20251014120845.2361-6-kundan.kumar@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251014120845.2361-6-kundan.kumar@samsung.com> X-Rspamd-Action: no action X-Stat-Signature: d8o4rpapoememb489ndatrrqk9xxz73t X-Rspamd-Queue-Id: 2A47D40003 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1761048346-245826 X-HE-Meta: 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 ubJvVPCk WSpGc5+wSmuA4OnV9AIqkkGpLqHJuyVJIy2xi3Pirr5e4YmpDoE2NsVEnNpvypsi9DX/Whl0EE+przaU9FV14Id4JM0S5oAjzqHVfJXt9WkVtu1s/FJ2gMmIyFi/CWSzAVA767AYa7qX6IrvORw8yl5UcbcZcmh02LK9IUsyaEo/6S64D1ERbMJ1wMHCZ5SK7aWJNVV40T278pKPDMR2EohnbgG4dJWXdOuxrJTzcuKoWNA/HwLy8XvNAi4JWTraH61hi0GgkGWLCLOUbKHyybSErve5tymrAg4BXXRf8Arm46JSspXgGap/ljaHzQRTH02lMuzzekzH6bpgLhviEI7pSF7Y7s8chr3wtWRsw2ZLNVGDM9H6BUJ4EPl7+HRHbYinvrX8v+Pjel9rC72fbnjOaJ1QGaFKpDjsh52g62zTMmmUD/HuHNIOk3SfN0VzQBlJ0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue 14-10-25 17:38:34, Kundan Kumar wrote: > Since we have multiple cgwb per bdi, embedded in writeback_ctx now, we > iterate over all of them to find the associated writeback. > > Signed-off-by: Kundan Kumar > Signed-off-by: Anuj Gupta > --- > fs/fs-writeback.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index 56c048e22f72..93f8ea340247 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -1090,7 +1090,8 @@ int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, > { > struct backing_dev_info *bdi; > struct cgroup_subsys_state *memcg_css; > - struct bdi_writeback *wb; > + struct bdi_writeback *wb = NULL; > + struct bdi_writeback_ctx *bdi_wb_ctx; > struct wb_writeback_work *work; > unsigned long dirty; > int ret; > @@ -1114,7 +1115,11 @@ int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, > * And find the associated wb. If the wb isn't there already > * there's nothing to flush, don't create one. > */ > - wb = wb_get_lookup(bdi->wb_ctx[0], memcg_css); > + for_each_bdi_wb_ctx(bdi, bdi_wb_ctx) { > + wb = wb_get_lookup(bdi_wb_ctx, memcg_css); > + if (wb) > + break; > + } This is wrong. We need to run writeback for all bdi_writeback structures for given memcg_css. Not just for the one we found first. Otherwise cgroup_writeback_by_id() wouldn't properly relieve the dirty pages pressure from a foreign dirtying of a memcg (see the big comment before mem_cgroup_track_foreign_dirty_slowpath() for more background on why cgroup_writeback_by_id() exists). Honza -- Jan Kara SUSE Labs, CR