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[2403:580d:fda1:0:2bb5:f164:6e6a:38d8]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c6a1878426sm39124445ad.64.2026.06.17.00.56.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Jun 2026 00:56:18 -0700 (PDT) Message-ID: <6260dd58-5b46-47f2-8c4c-382bc470b5aa@suse.com> Date: Wed, 17 Jun 2026 17:26:14 +0930 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] btrfs: emit BTRFS_SEND_C_FILEATTR during full send To: Mateusz Poliwczak , clm@fb.com, dsterba@suse.com Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <62a6fc38-f204-45fd-b924-6cca98c6a2c1@suse.com> <20260617070112.1407453-1-mpoliwczak34@gmail.com> 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: <20260617070112.1407453-1-mpoliwczak34@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/6/17 16:26, Mateusz Poliwczak 写道: > Currently BTRFS_SEND_C_FILEATTR is only emitted during incremental > send when fileattr change between snapshots. This change makes sure > we also emit BTRFS_SEND_C_FILEATTR when sending the full snapshot. > > Without this there is no way to gain access to the fileattr of a file > e.g. the FS_NOCOW_FL flag without doing a separate FS_IOC_GETFLAGS > syscall, which might not be even possible if the stream is send over > network or such. Unfortunately, btrfs receive will just ignore those fileattrs. It's a known limit: https://github.com/kdave/btrfs-progs/issues/1057#issuecomment-3492918443 The reason is that different file attrs will require completely different handling. From NODATACOW/NODATASUM which can only be set for empty file, to immutable flags handling. So this patch will not do any difference, and the whole situation is a very deep rabbit hole. If you want to address this problem, please check this issue first: https://github.com/kdave/btrfs-progs/issues/526 > > Signed-off-by: Mateusz Poliwczak > --- > fs/btrfs/send.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c > index 3ae480c7474b..effbe7ac1a81 100644 > --- a/fs/btrfs/send.c > +++ b/fs/btrfs/send.c > @@ -6575,8 +6575,10 @@ static int finish_inode_if_needed(struct send_ctx *sctx, bool at_end) > > if (!sctx->parent_root || sctx->cur_inode_new) { > need_chown = true; > - if (!S_ISLNK(sctx->cur_inode_mode)) > + if (!S_ISLNK(sctx->cur_inode_mode)) { > need_chmod = true; > + need_fileattr = true; > + } > if (sctx->cur_inode_next_write_offset == sctx->cur_inode_size) > need_truncate = false; > } else {