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bh=fg12LtZtOspmaccAffL7mh6KvLvmqhbCNnsVhtX9ISI=; b=xnDrNcPvw2qsj1rAwEhdtSVjz7DjjxiYIlX8fzryFu6C0BMoN3zyfSVsE5z52aqVDUiW4e zjAnR7pFuFltqsl4ZroXhNLfmGciOQFolToyfLbO1KFO9KaOIZE43NZMvsvbYnEfeNtLP5 Wk448vsA0dQKPZAFX8XJPC8dfs6DjTs= X-Rspamd-Queue-Id: 2F8B71C003F X-Rspam-User: Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=PtQCyBHK; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf21.hostedemail.com: domain of 3xZe_YggKCBA8xq0uu1rw44w1u.s421y3AD-220Bqs0.47w@flex--shakeelb.bounces.google.com designates 209.85.128.201 as permitted sender) smtp.mailfrom=3xZe_YggKCBA8xq0uu1rw44w1u.s421y3AD-220Bqs0.47w@flex--shakeelb.bounces.google.com X-Rspamd-Server: rspam02 X-Stat-Signature: 9uj4u9546ghba56qgbwan5kw8eupwifn X-HE-Tag: 1656723397-729563 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000028, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jul 01, 2022 at 02:08:26PM -0600, Jens Axboe wrote: > If we're creating a page cache page with FGP_CREAT but FGP_NOWAIT is > set, we should dial back the gfp flags to avoid frivolous blocking > which is trivial to hit in low memory conditions: > > [ 10.117661] __schedule+0x8c/0x550 > [ 10.118305] schedule+0x58/0xa0 > [ 10.118897] schedule_timeout+0x30/0xdc > [ 10.119610] __wait_for_common+0x88/0x114 > [ 10.120348] wait_for_completion+0x1c/0x24 > [ 10.121103] __flush_work.isra.0+0x16c/0x19c > [ 10.121896] flush_work+0xc/0x14 > [ 10.122496] __drain_all_pages+0x144/0x218 > [ 10.123267] drain_all_pages+0x10/0x18 > [ 10.123941] __alloc_pages+0x464/0x9e4 > [ 10.124633] __folio_alloc+0x18/0x3c > [ 10.125294] __filemap_get_folio+0x17c/0x204 > [ 10.126084] iomap_write_begin+0xf8/0x428 > [ 10.126829] iomap_file_buffered_write+0x144/0x24c > [ 10.127710] xfs_file_buffered_write+0xe8/0x248 > [ 10.128553] xfs_file_write_iter+0xa8/0x120 > [ 10.129324] io_write+0x16c/0x38c > [ 10.129940] io_issue_sqe+0x70/0x1cc > [ 10.130617] io_queue_sqe+0x18/0xfc > [ 10.131277] io_submit_sqes+0x5d4/0x600 > [ 10.131946] __arm64_sys_io_uring_enter+0x224/0x600 > [ 10.132752] invoke_syscall.constprop.0+0x70/0xc0 > [ 10.133616] do_el0_svc+0xd0/0x118 > [ 10.134238] el0_svc+0x78/0xa0 > > Clear IO, FS, and reclaim flags and mark the allocation as nowarn, > as FGP_NOWAIT are expected to be able to handle -EAGAIN failures and > retry from a suitable context without NOWAIT set. > > Signed-off-by: Jens Axboe > --- > mm/filemap.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/filemap.c b/mm/filemap.c > index ffdfbc8b0e3c..9b747d3247c6 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1988,6 +1988,10 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, > gfp |= __GFP_WRITE; > if (fgp_flags & FGP_NOFS) > gfp &= ~__GFP_FS; > + if (fgp_flags & FGP_NOWAIT) { > + gfp &= ~GFP_KERNEL; Do you think the semantic of FGP_NOWAIT should be similar to GFP_NOWAIT? That is allow kswapd wakeup. > + gfp |= __GFP_NOWARN; > + } > > folio = filemap_alloc_folio(gfp, 0); > if (!folio) > -- > 2.35.1 > > -- > Jens Axboe > >