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Bottomley" , Helge Deller , "John David Anglin" , , "Filipe Manana" Subject: Re: [PATCH v5 2/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Message-ID: References: <20220704152322.20955-1-fmdefrancesco@gmail.com> <20220704152322.20955-3-fmdefrancesco@gmail.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20220704152322.20955-3-fmdefrancesco@gmail.com> X-ClientProxiedBy: BYAPR05CA0017.namprd05.prod.outlook.com (2603:10b6:a03:c0::30) To DM4PR11MB6311.namprd11.prod.outlook.com (2603:10b6:8:a6::21) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: d574cba3-752b-479f-15a9-08da5eb9256c X-MS-TrafficTypeDiagnostic: DM8PR11MB5736:EE_ X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM4PR11MB6311.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230016)(7916004)(346002)(396003)(366004)(39860400002)(376002)(136003)(478600001)(6486002)(38100700002)(186003)(6506007)(41300700001)(6666004)(2906002)(316002)(54906003)(82960400001)(8936002)(7416002)(44832011)(5660300002)(86362001)(6916009)(9686003)(6512007)(83380400001)(66946007)(66476007)(66556008)(33716001)(4326008)(8676002);DIR:OUT;SFP:1102; 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De Francesco wrote: > The use of kmap() is being deprecated in favor of kmap_local_page(). With > kmap_local_page(), the mapping is per thread, CPU local and not globally > visible. > > Therefore, use kmap_local_page() / kunmap_local() in zstd.c because in this > file the mappings are per thread and are not visible in other contexts. In > the meanwhile use plain page_address() on pages allocated with the GFP_NOFS > flag instead of calling kmap*() on them (since they are always allocated > from ZONE_NORMAL). > > Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM and > booting a kernel with HIGHMEM64G enabled. > > Cc: Filipe Manana > Suggested-by: Ira Weiny > Signed-off-by: Fabio M. De Francesco > --- > fs/btrfs/zstd.c | 34 ++++++++++++++-------------------- > 1 file changed, 14 insertions(+), 20 deletions(-) > > diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c > index 0fe31a6f6e68..78e0272e770e 100644 > --- a/fs/btrfs/zstd.c > +++ b/fs/btrfs/zstd.c > @@ -403,7 +403,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, > > /* map in the first page of input data */ > in_page = find_get_page(mapping, start >> PAGE_SHIFT); > - workspace->in_buf.src = kmap(in_page); > + workspace->in_buf.src = kmap_local_page(in_page); > workspace->in_buf.pos = 0; > workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE); > > @@ -415,7 +415,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, > goto out; > } > pages[nr_pages++] = out_page; > - workspace->out_buf.dst = kmap(out_page); > + workspace->out_buf.dst = page_address(out_page); > workspace->out_buf.pos = 0; > workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE); > > @@ -450,9 +450,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, > if (workspace->out_buf.pos == workspace->out_buf.size) { > tot_out += PAGE_SIZE; > max_out -= PAGE_SIZE; > - kunmap(out_page); > if (nr_pages == nr_dest_pages) { > - out_page = NULL; > ret = -E2BIG; > goto out; > } > @@ -462,7 +460,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, > goto out; > } > pages[nr_pages++] = out_page; > - workspace->out_buf.dst = kmap(out_page); > + workspace->out_buf.dst = page_address(out_page); > workspace->out_buf.pos = 0; > workspace->out_buf.size = min_t(size_t, max_out, > PAGE_SIZE); > @@ -477,15 +475,15 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, > /* Check if we need more input */ > if (workspace->in_buf.pos == workspace->in_buf.size) { > tot_in += PAGE_SIZE; > - kunmap(in_page); > + kunmap_local(workspace->in_buf.src); > put_page(in_page); > - > start += PAGE_SIZE; > len -= PAGE_SIZE; > in_page = find_get_page(mapping, start >> PAGE_SHIFT); > - workspace->in_buf.src = kmap(in_page); > + workspace->in_buf.src = kmap_local_page(in_page); > workspace->in_buf.pos = 0; > workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE); > + workspace->out_buf.dst = page_address(out_page); Why is this needed? The rest looks good, Ira [snip]