Re: [PATCH 03/18] MM: use ->swap_rw for reads from SWP_FS_OPS swap-space
From: Mark Hemment <hidden>
Date: 2021-12-20 12:16:43
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linux-nfs, lkml
On Thu, 16 Dec 2021 at 23:54, NeilBrown [off-list ref] wrote:
To submit an async read with ->swap_rw() we need to allocate a structure to hold the kiocb and other details. swap_readpage() cannot handle transient failure, so create a mempool to provide the structures. Signed-off-by: NeilBrown <redacted> --- mm/page_io.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++------ mm/swap.h | 1 + mm/swapfile.c | 5 +++++ 3 files changed, 58 insertions(+), 6 deletions(-)
...
quoted hunk ↗ jump to hunk
diff --git a/mm/swapfile.c b/mm/swapfile.c index f23d9ff21cf8..43539be38e68 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c@@ -2401,6 +2401,11 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) if (ret < 0) return ret; sis->flags |= SWP_ACTIVATED; + if ((sis->flags & SWP_FS_OPS) && + sio_pool_init() != 0) { + destroy_swap_extents(sis); + return -ENOMEM; + } return ret; }
This code is called before 'swapon_mutex' is taken in the swapon code path, so possible for multiple swapons to race here creating two (or more) memory pools. Mark