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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23c84598b70sm57453105ad.204.2025.07.05.20.37.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 05 Jul 2025 20:37:25 -0700 (PDT) Message-ID: <6642f8b5-d357-4fb6-a295-906178a633f9@suse.com> Date: Sun, 6 Jul 2025 13:07:19 +0930 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 v4 5/6] btrfs: implement shutdown ioctl To: dsterba@suse.cz Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz References: <5ff44de2d9d7f8c2e59fa3a5fe68d5bb4c71a111.1751589725.git.wqu@suse.com> <20250705142230.GC4453@twin.jikos.cz> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20250705142230.GC4453@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/7/5 23:52, David Sterba 写道: > On Fri, Jul 04, 2025 at 10:12:33AM +0930, Qu Wenruo wrote: >> The shutdown ioctl should follow the XFS one, which use magic number 'X', >> and ioctl number 125, with a u32 as flags. >> >> For now btrfs don't distinguish DEFAULT and LOGFLUSH flags (just like >> f2fs), both will freeze the fs first (implies committing the current >> transaction), setting the SHUTDOWN flag and finally thaw the fs. >> >> For NOLOGFLUSH flag, the freeze/thaw part is skipped thus the current >> transaction is aborted. >> >> The new shutdown ioctl is hidden behind experimental features for more >> testing. >> >> Signed-off-by: Qu Wenruo >> --- >> fs/btrfs/ioctl.c | 40 ++++++++++++++++++++++++++++++++++++++ >> include/uapi/linux/btrfs.h | 9 +++++++++ >> 2 files changed, 49 insertions(+) >> >> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c >> index 2f3b7be13bea..94eb7a8499db 100644 >> --- a/fs/btrfs/ioctl.c >> +++ b/fs/btrfs/ioctl.c >> @@ -5194,6 +5194,36 @@ static int btrfs_ioctl_subvol_sync(struct btrfs_fs_info *fs_info, void __user *a >> return 0; >> } >> >> +#ifdef CONFIG_BTRFS_EXPERIMENTAL >> +static int btrfs_emergency_shutdown(struct btrfs_fs_info *fs_info, u32 flags) >> +{ >> + int ret = 0; >> + >> + if (flags >= BTRFS_SHUTDOWN_FLAGS_LAST) >> + return -EINVAL; >> + >> + if (btrfs_is_shutdown(fs_info)) >> + return 0; >> + >> + switch (flags) { >> + case BTRFS_SHUTDOWN_FLAGS_LOGFLUSH: >> + case BTRFS_SHUTDOWN_FLAGS_DEFAULT: >> + ret = freeze_super(fs_info->sb, FREEZE_HOLDER_KERNEL, NULL); > > Recently I've looked at scrub blocking filesystem freezing and it does > not work because it blocks on the semaphore taken in mnt_want_write, > also taken in freeze_super(). > > I have an idea for fix, basically pause scrub, undo mnt_want_write > and then call freeze_super. So we'll need that too for shutdown. Once > implemented the fixup would be to use btrfs_freeze_super callback here. It may not be that simple. freeze_super() itself is doing extra works related to the stage/freeze_owner/etc. I'm not sure if it's a good idea to completely skip that part. I'd prefer scrub to check the frozen stage, and if it's already in any FREEZE stages, exit early. Thanks, Qu > >> + if (ret) >> + return ret; >> + btrfs_force_shutdown(fs_info); >> + ret = thaw_super(fs_info->sb, FREEZE_HOLDER_KERNEL, NULL); >> + if (ret) >> + return ret; >> + break; >> + case BTRFS_SHUTDOWN_FLAGS_NOLOGFLUSH: >> + btrfs_force_shutdown(fs_info); >> + break; >> + } >> + return ret; >> +} >> +#endif >> + >> long btrfs_ioctl(struct file *file, unsigned int >> cmd, unsigned long arg) >> { > >> --- a/include/uapi/linux/btrfs.h >> +++ b/include/uapi/linux/btrfs.h >> @@ -1096,6 +1096,12 @@ enum btrfs_err_code { >> BTRFS_ERROR_DEV_RAID1C4_MIN_NOT_MET, >> }; >> >> +/* Flags for IOC_SHUTDOWN, should match XFS' flags. */ >> +#define BTRFS_SHUTDOWN_FLAGS_DEFAULT 0x0 >> +#define BTRFS_SHUTDOWN_FLAGS_LOGFLUSH 0x1 >> +#define BTRFS_SHUTDOWN_FLAGS_NOLOGFLUSH 0x2 >> +#define BTRFS_SHUTDOWN_FLAGS_LAST 0x3 >> + >> #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \ >> struct btrfs_ioctl_vol_args) >> #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \ >> @@ -1217,6 +1223,9 @@ enum btrfs_err_code { >> #define BTRFS_IOC_SUBVOL_SYNC_WAIT _IOW(BTRFS_IOCTL_MAGIC, 65, \ >> struct btrfs_ioctl_subvol_wait) >> >> +/* Shutdown ioctl should follow XFS's interfaces, thus not using btrfs magic. */ >> +#define BTRFS_IOC_SHUTDOWN _IOR('X', 125, __u32) > > In XFS it's > > #define XFS_IOC_GOINGDOWN _IOR ('X', 125, uint32_t) > > It's right to use the same definition and ioctl value as this will > be a generic ioctl eventually, with 3 users at least. I like the name > SHUTDOWN better, ext4 also uses that.