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Tue, 08 Oct 2024 22:58:13 +0200 Message-ID: <3a5b435b-7790-4499-8501-9ae3646f3377@gmx.com> Date: Wed, 9 Oct 2024 07:28:09 +1030 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] btrfs: fix the delalloc range locking if sector size < page size To: dsterba@suse.cz, Qu Wenruo Cc: linux-btrfs@vger.kernel.org References: <305e53f3931e164c8ab3b09c059ea68bd792a4b2.1728256845.git.wqu@suse.com> <20241008165833.GD1609@twin.jikos.cz> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00iVQUJDToH pgAKCRDCPZHzoSX+qNKACACkjDLzCvcFuDlgqCiS4ajHAo6twGra3uGgY2klo3S4JespWifr BLPPak74oOShqNZ8yWzB1Bkz1u93Ifx3c3H0r2vLWrImoP5eQdymVqMWmDAq+sV1Koyt8gXQ XPD2jQCrfR9nUuV1F3Z4Lgo+6I5LjuXBVEayFdz/VYK63+YLEAlSowCF72Lkz06TmaI0XMyj jgRNGM2MRgfxbprCcsgUypaDfmhY2nrhIzPUICURfp9t/65+/PLlV4nYs+DtSwPyNjkPX72+ LdyIdY+BqS8cZbPG5spCyJIlZonADojLDYQq4QnufARU51zyVjzTXMg5gAttDZwTH+8LbNI4 mm2YzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00ibgUJDToHvwAK CRDCPZHzoSX+qK6vB/9yyZlsS+ijtsvwYDjGA2WhVhN07Xa5SBBvGCAycyGGzSMkOJcOtUUf tD+ADyrLbLuVSfRN1ke738UojphwkSFj4t9scG5A+U8GgOZtrlYOsY2+cG3R5vjoXUgXMP37 INfWh0KbJodf0G48xouesn08cbfUdlphSMXujCA8y5TcNyRuNv2q5Nizl8sKhUZzh4BascoK DChBuznBsucCTAGrwPgG4/ul6HnWE8DipMKvkV9ob1xJS2W4WJRPp6QdVrBWJ9cCdtpR6GbL iQi22uZXoSPv/0oUrGU+U5X4IvdnvT+8viPzszL5wXswJZfqfy8tmHM85yjObVdIG6AlnrrD In-Reply-To: <20241008165833.GD1609@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:Wndrmv0RPMQjA+EqOxmVPKMkyNy4U/D7ZiCn7Ztx8TwEIyaEka7 4v8kbE+UXWTZsItTaBU2q7lMkDXKuC+xwfV2nHI1JNt8aqjfV9KfVRtF4xy18KzxOTY5May keDheQL83ugkqYsmcmIo2EO0jHSW10iu8eGKQdIUjvYgSmq5Mo9Kk4ucbjnNLlnBayJgASZ A7sovpbXcxxyo6v5RsZbQ== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:1Dkak0H3VFw=;3l9lSpPUrGUAC1QxWJbMXJpgpS5 Wh21IWBJvVcufkMLAAcigoDFLg31GW7/hnxM5bVa0T6i0THwJHykJk+vURWjnInsgyh4JYpsV kN9Fy1DbCFU4Q6d9dzIh35ezYvf6XnRgl5z/8jzwlLtSZGOcGJVmwiEekNWveTVFc9bnMSXOL gJCEjMXZ5+u7NoJFtOT9hkJfmKnIhMTvqyD25yHmtpRFAwz7Y7+gIZdRBTTiMiccNZ15KuK8B dh4ll7drDhKZOmKZgKnzzNk2pyP3t7y8b6oROH+B0vrkjI3IUij7Pp3IuH3hsKBxSO+xlAeHq LiQI6nseegipDCiBCwA6mnjRk8r2jCUv9Xg75ZVTcV/xn6n2cjHvSSBk2U2QnqgsojddJ3+I4 qd7xggXjmw+OKOewjf059Buxw7UmfUkInTMuPELvDT7OsD2RIz1je0rDkeQOmQFixAdDzDP7D tGhs1HWEyeVYs+KnTFmb+4uuri+Tz4rH+Wk/TfH4hqAIooWzIffAVh7wlxdEW3zsKvJYo2mC0 uVAWDX8GqgbqJyJNF8yI1VcSeVrkHDpp85pHu5ke6/+fC7fYTFmvLC9AVQoFeuToKICOi+KLG 42JnukoT0N3uYt2jGUtlHVR8fR+Fcmtk5zblpcYiJC8iGhCns9KU/3RdovAmFKAoDQTvvM5Xj 3b6+XtoXiHIwBsK18U//jL1uRzj8wrFny/7SbCyZ26gsxdJYYAu35pQNRZc3On1FAWdxIlrAf FD0gOnuuhWt6LiBMst/eQXqJIPNvWU8ksKlwyeE+vUCtvT2XKsr4jeqQf0xkJAVs4Dk5OUMo9 7OyAK1f+rRdEHZzHf28/xebQ== =E5=9C=A8 2024/10/9 03:28, David Sterba =E5=86=99=E9=81=93: > On Mon, Oct 07, 2024 at 09:51:40AM +1030, Qu Wenruo wrote: >> Inside lock_delalloc_folios(), there are several problems related to >> sector size < page size handling: >> >> - Set the writer locks without checking if the folio is still valid >> We call btrfs_folio_start_writer_lock() just like it's folio_lock(). >> But since the folio may not even be the folio of the current mapping= , >> we can easily screw up the folio->private. >> >> - The range is not clampped inside the page >> This means we can over write other bitmaps if the start/len is not >> properly handled, and trigger the btrfs_subpage_assert(). >> >> - @processed_end is always rounded up to page end >> If the delalloc range is not page aligned, and we need to retry >> (returning -EAGAIN), then we will unlock to the page end. >> >> Thankfully this is not a huge problem, as now >> btrfs_folio_end_writer_lock() can handle range larger than the locke= d >> range, and only unlock what is already locked. >> >> Fix all these problems by: >> >> - Lock and check the folio first, then call >> btrfs_folio_set_writer_lock() >> So that if we got a folio not belonging to the inode, we won't >> touch folio->private. >> >> - Properly truncate the range inside the page >> >> - Update @processed_end to the locked range end >> >> - Remove btrfs_folio_start_writer_lock() >> Since all callsites only utilize btrfs_folio_set_writer_lock() now, >> remove the unnecessary btrfs_folio_start_writer_lock(). >> >> Fixes: 1e1de38792e0 ("btrfs: make process_one_page() to handle subpage = locking") > > This commit is in 5.14, so we'd need backport to 5.15+. The v1 would be > more suitable as it does not remove the unused > btrfs_folio_start_writer_lock(). As it's exported function there should > be no warning. > >> Signed-off-by: Qu Wenruo >> --- >> Changelog: >> v2: >> - Remove the unused btrfs_folio_start_writer_lock() function >> --- >> fs/btrfs/extent_io.c | 15 +++++++------- >> fs/btrfs/subpage.c | 47 -------------------------------------------= - >> fs/btrfs/subpage.h | 2 -- >> 3 files changed, 7 insertions(+), 57 deletions(-) >> >> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c >> index e0b43640849e..0448cee2b983 100644 >> --- a/fs/btrfs/extent_io.c >> +++ b/fs/btrfs/extent_io.c >> @@ -262,22 +262,21 @@ static noinline int lock_delalloc_folios(struct i= node *inode, >> >> for (i =3D 0; i < found_folios; i++) { >> struct folio *folio =3D fbatch.folios[i]; >> - u32 len =3D end + 1 - start; >> + u64 range_start =3D max_t(u64, folio_pos(folio), start); >> + u32 range_len =3D min_t(u64, folio_pos(folio) + folio_size(folio), >> + end + 1) - range_start; >> >> if (folio =3D=3D locked_folio) >> continue; >> >> - if (btrfs_folio_start_writer_lock(fs_info, folio, start, >> - len)) >> - goto out; >> - >> + folio_lock(folio); >> if (!folio_test_dirty(folio) || folio->mapping !=3D mapping) { > > Should the range_start and range_end be set after folio_lock? One of the > prolblems you're fixing is the folio and mapping mismatch, if I read it > correctly. > Nice catch, indeed that's the problem. Will fix it and split out the cleanup in the next version. Thanks, Qu