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Fri, 16 Feb 2024 01:17:03 -0800 (PST) MIME-Version: 1.0 References: <20240216030539.110404-1-21cnbao@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Fri, 16 Feb 2024 17:16:50 +0800 Message-ID: Subject: Re: [PATCH] mm: zswap: increase reject_compress_poor but not reject_compress_fail if compression returns ENOSPC To: Chengming Zhou , Yosry Ahmed Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song , Nhat Pham , Sergey Senozhatsky Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 9CA7514001E X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 46gcas3bcd6qi83swug7cwe4u7bxa3j6 X-HE-Tag: 1708075024-969539 X-HE-Meta: U2FsdGVkX19qV/I7coRrwg7dddaIw13WsuaYrgolzyUeK9isOnI+MdJQTvZSCxA26ucyRGfrPrO01aeg2NEiPZKEBQRZ1FR0+ZGd02AVoe+5Xr5LQ6IcTMX6XE2yLerqA11Ijj++98BUF0eRejippUDeBbp//cPTxZ4JiaclnPd24i3e83gUiFpEvpLwywqqxEsCog75LbAf7tguCRBX2+KpSZdAU18y4K0TUaiLk2I2q1O9HLGnx9Bd9HW2hnEx78e8jXcpVygZmgur74VDIWBV8f1oaIBFY7UtNFg9+jtoMfhoJtR3li8loRRryOuWj9oSeNPiMtN0fnUT2KmuCDqiSDakoxIr1KZsaxbDvSGG/W4pBLQz2PmuIUtIcuydIJTjr+qNHKhcjpSuT5w5AXcgb+kELGYYpFfKsmaXwXEyaDXnHlRcpYVXULI7pa3Z7efGTr0yrC8LDp55mZnfA7dhShgS0VSnhWV0yeQnWWBS8GFtTrAQQ38Nw+F3919ZZdvoCX8LmSwN4/lZGmmGNdXRWv191bZN56A1Taa0mSvcvQFw29IxMEXwQY8ID0ECP3XZNoxIWZj/aW/HLPM1aInzQr+ezAjw5+bMUCbwpgrKNBrjDa7F35u/HKibdjkHntbNmjxWPpeLwU83LxIS27vj4lslGQ3sPVrJVsHep8wS3ZaFPBBSv3wGFEuiOZdCfdtTbU+oK4twU/rfQGLRbhzfnxTtCakGHxjTbIP9XGDU5zLVOx+/DkC3Tq0nWVcMJIkTXY+P6bZqPXShmu1YE4mxVWwZqnFj+KrgV7vWmFK1ua4X8PdRvn0jhRzr9T6zZ4IzQIiwIpQbUlQVCVqTOnnVLnHf+wr9JTjmGTjoPgHPdFLW58C2jrsmQaAoBPDFQsqJnddRHdPgwNwZcNmdgLfFde+rh+PLpMPWc6sx46INPKRuo6/4Vwzm5cfjLrYDg/79JveqKNbpcYsZAMG ggjvl/J5 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 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 Fri, Feb 16, 2024 at 5:07=E2=80=AFPM Chengming Zhou wrote: > > On 2024/2/16 16:23, Yosry Ahmed wrote: > > On Fri, Feb 16, 2024 at 04:05:39PM +1300, Barry Song wrote: > >> From: Barry Song > >> > >> My commit fc8580edbaa6 ("mm: zsmalloc: return -ENOSPC rather than -EIN= VAL > >> in zs_malloc while size is too large") wanted to depend on zs_malloc's > >> returned ENOSPC to distinguish the case that compressed data is larger > >> than the original data from normal compression cases. The commit, for > >> sure, was correct and worked as expected but the code wouldn't run to > >> there after commit 744e1885922a ("crypto: scomp - fix req->dst buffer > >> overflow") as Chengming's this patch makes zswap_store() goto out > >> immediately after the special compression case happens. So there is > >> no chance to execute zs_malloc() now. We need to fix the count right > >> after compressions return ENOSPC. > >> > >> Fixes: fc8580edbaa6 ("mm: zsmalloc: return -ENOSPC rather than -EINVAL= in zs_malloc while size is too large") > > > > I don't see how this is a fix for that commit. Commit fc8580edbaa6 made > > sure zsmalloc returns a correct errno when the compressed size is too > > large. The fact that zswap stores were failing before calling into > > zsmalloc and not reporting the error correctly in debug counters is not > > that commits fault. > > Hi Yosry, Chengming, Thanks for your quick responses. > > I think the proper fixes should be 744e1885922a if it introduced the > > first scenario where -ENOSPC can be returned from scomp without handlin= g > > it properly in zswap. If -ENOSPC was a possible return value before > > that, then it should be cb61dad80fdc ("zswap: export compression failur= e > > stats"), where the counter was introduced. > > Right, 744e1885922a maybe a better fixes target. I agree 744e1885922a is a better fixes target. > > > > >> Cc: Chengming Zhou > >> Cc: Nhat Pham > >> Cc: Sergey Senozhatsky > >> Signed-off-by: Barry Song > >> --- > >> mm/zswap.c | 5 ++++- > >> 1 file changed, 4 insertions(+), 1 deletion(-) > >> > >> diff --git a/mm/zswap.c b/mm/zswap.c > >> index 6319d2281020..9a21dbe8c056 100644 > >> --- a/mm/zswap.c > >> +++ b/mm/zswap.c > >> @@ -1627,7 +1627,10 @@ bool zswap_store(struct folio *folio) > >> dlen =3D acomp_ctx->req->dlen; > >> > >> if (ret) { > >> - zswap_reject_compress_fail++; > >> + if (ret =3D=3D -ENOSPC) > >> + zswap_reject_compress_poor++; > >> + else > >> + zswap_reject_compress_fail++; > > > > With this diff, we have four locations in zswap_store() where we > > increment zswap_reject_compress_{poor/fail}. > > > > How about the following instead?A > > > > diff --git a/mm/zswap.c b/mm/zswap.c > > index 62fe307521c93..3a7e8ba7f6116 100644 > > --- a/mm/zswap.c > > +++ b/mm/zswap.c > > @@ -1059,24 +1059,16 @@ static bool zswap_compress(struct folio *folio,= struct zswap_entry *entry) > > */ > > ret =3D crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &a= comp_ctx->wait); > > dlen =3D acomp_ctx->req->dlen; > > - if (ret) { > > - zswap_reject_compress_fail++; > > + if (ret) > > goto unlock; > > - } > > > > zpool =3D zswap_find_zpool(entry); > > gfp =3D __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM; > > if (zpool_malloc_support_movable(zpool)) > > gfp |=3D __GFP_HIGHMEM | __GFP_MOVABLE; > > ret =3D zpool_malloc(zpool, dlen, gfp, &handle); > > - if (ret =3D=3D -ENOSPC) { > > - zswap_reject_compress_poor++; > > - goto unlock; > > - } > > - if (ret) { > > - zswap_reject_alloc_fail++; > > + if (ret) > > goto unlock; > > - } > > > > buf =3D zpool_map_handle(zpool, handle, ZPOOL_MM_WO); > > memcpy(buf, dst, dlen); > > @@ -1086,6 +1078,10 @@ static bool zswap_compress(struct folio *folio, = struct zswap_entry *entry) > > entry->length =3D dlen; > > > > unlock: > > + if (ret =3D=3D -ENOSPC) > > + zswap_reject_compress_poor++; > > + else if (ret) > > + zswap_reject_alloc_fail++; > > Here have two cases: zswap_reject_compress_fail, zswap_reject_alloc_fail. Is it safe to differentiate these two cases by checking ret =3D=3D -ENOMEM = ? otherwise, it seems the original patch still makes more sense? > > > mutex_unlock(&acomp_ctx->mutex); > > return ret =3D=3D 0; > > } > > > >> goto put_dstmem; > >> } > >> > >> -- > >> 2.34.1 > >> Thanks Barry