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Mon, 9 Mar 2026 20:11:03 +0000 (GMT) Message-ID: <0bd92b4fce00a6111a0fc7764904f7e6ae0ece3a.camel@linux.ibm.com> Subject: Re: [PATCH v3 00/12] vfs: change inode->i_ino from unsigned long to u64 From: Mimi Zohar To: Jeff Layton Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, nvdimm@lists.linux.dev, fsverity@lists.linux.dev, linux-mm@kvack.org, netfs@lists.linux.dev, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-nilfs@vger.kernel.org, v9fs@lists.linux.dev, linux-afs@lists.infradead.org, autofs@vger.kernel.org, ceph-devel@vger.kernel.org, codalist@coda.cs.cmu.edu, ecryptfs@vger.kernel.org, linux-mtd@lists.infradead.org, jfs-discussion@lists.sourceforge.net, ntfs3@lists.linux.dev, ocfs2-devel@lists.linux.dev, devel@lists.orangefs.org, linux-unionfs@vger.kernel.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, netdev@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-xfs@vger.kernel.org, linux-hams@vger.kernel.org, linux-x25@vger.kernel.org, audit@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-can@vger.kernel.org, linux-sctp@vger.kernel.org, bpf@vger.kernel.org In-Reply-To: References: <20260304-iino-u64-v3-0-2257ad83d372@kernel.org> <05b5d55c49b5a1bbc43a5315e3c84872e7e634b3.camel@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Mon, 09 Mar 2026 16:11:02 -0400 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=EK4LElZC c=1 sm=1 tr=0 ts=69af295b cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=Ohuc5M0UGw20_VvRb6sA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzA5MDE3OCBTYWx0ZWRfX48NInAXNxJ9I cqZ2w42oLBKp6f6ShdJYkvtWo35W1xBR9wJ3/AMrAgqtjjRmHF+LNmGqeG928jRHEGfhi5Dc3Ir wmrxB6T58L1jgUeut/UN4ASDb+YKdYMu+ThxKOBJOKt26YDnsAlMtjSvmCcaxE+TT5Ibe0zYC0f zBgbUGDl6m62+LPcwjv67C82HPGKVuU4mQ7dUKg2Sv0H9xprcqNV55N1hEVQyFV4pb7QXKtAhGE YVUSx215hmiPcMqQdaRgfBi/PErZi+WGgzrtD+EeiIqh5iBJfaUE0yW08tvcIRwoQr42lAufyzB vYZKyixwfkjfLVLXUjHMdBtRGJrXaAm82jJw9wIV+5PYqMOONm6AlqMVRpwFh8k3h3nwk8wQiR2 zhIg8VMnQ/RF3WK3QDU7+acPMfehsyHGr854HkqAG/4Nm9pp74q0YkbWa+CcmHp5NJJ/sMPIvY9 s27fVbRyzlJIijxgTKg== X-Proofpoint-GUID: xB1hrjZmRj2bIZxp5d4ApU8QU-_XE2VB X-Proofpoint-ORIG-GUID: xB1hrjZmRj2bIZxp5d4ApU8QU-_XE2VB X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-09_05,2026-03-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 spamscore=0 suspectscore=0 clxscore=1015 bulkscore=0 impostorscore=0 priorityscore=1501 malwarescore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603090178 On Mon, 2026-03-09 at 15:33 -0400, Jeff Layton wrote: > On Mon, 2026-03-09 at 15:00 -0400, Mimi Zohar wrote: > > On Mon, 2026-03-09 at 13:59 -0400, Jeff Layton wrote: > > > On Mon, 2026-03-09 at 13:47 -0400, Mimi Zohar wrote: > > > > [ I/O socket time out. Trimming the To list.] > > > >=20 > > > > On Wed, 2026-03-04 at 10:32 -0500, Jeff Layton wrote: > > > > > This version squashes all of the format-string changes and the i_= ino > > > > > type change into the same patch. This results in a giant 600+ lin= e patch > > > > > at the end of the series, but it does remain bisectable. Because= the > > > > > patchset was reorganized (again) some of the R-b's and A-b's have= been > > > > > dropped. > > > > >=20 > > > > > The entire pile is in the "iino-u64" branch of my tree, if anyone= is > > > > > interested in testing this. > > > > >=20 > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux= .git/ > > > > >=20 > > > > > Original cover letter follows: > > > > >=20 > > > > > ----------------------8<----------------------- > > > > >=20 > > > > > Christian said [1] to "just do it" when I proposed this, so here = we are! > > > > >=20 > > > > > For historical reasons, the inode->i_ino field is an unsigned lon= g, > > > > > which means that it's 32 bits on 32 bit architectures. This has c= aused a > > > > > number of filesystems to implement hacks to hash a 64-bit identif= ier > > > > > into a 32-bit field, and deprives us of a universal identifier fi= eld for > > > > > an inode. > > > > >=20 > > > > > This patchset changes the inode->i_ino field from an unsigned lon= g to a > > > > > u64. This shouldn't make any material difference on 64-bit hosts,= but > > > > > 32-bit hosts will see struct inode grow by at least 4 bytes. This= could > > > > > have effects on slabcache sizes and field alignment. > > > > >=20 > > > > > The bulk of the changes are to format strings and tracepoints, si= nce the > > > > > kernel itself doesn't care that much about the i_ino field. The f= irst > > > > > patch changes some vfs function arguments, so check that one out > > > > > carefully. > > > > >=20 > > > > > With this change, we may be able to shrink some inode structures.= For > > > > > instance, struct nfs_inode has a fileid field that holds the 64-b= it > > > > > inode number. With this set of changes, that field could be elimi= nated. > > > > > I'd rather leave that sort of cleanups for later just to keep thi= s > > > > > simple. > > > > >=20 > > > > > Much of this set was generated by LLM, but I attributed it to mys= elf > > > > > since I consider this to be in the "menial tasks" category of LLM= usage. > > > > >=20 > > > > > [1]: https://lore.kernel.org/linux-fsdevel/20260219-portrait-wink= t-959070cee42f@brauner/ > > > > >=20 > > > > > Signed-off-by: Jeff Layton > > > >=20 > > > > Jeff, missing from this patch set is EVM. In hmac_add_misc() EVM c= opies the > > > > i_ino and calculates either an HMAC or file meta-data hash, which i= s then > > > > signed.=20 > > > >=20 > > > >=20 > > >=20 > > > Thanks Mimi, good catch. > > >=20 > > > It looks like we should just be able to change the ino field to a u64 > > > alongside everything else. Something like this: > > >=20 > > > diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity= /evm/evm_crypto.c > > > index c0ca4eedb0fe..77b6c2fa345e 100644 > > > --- a/security/integrity/evm/evm_crypto.c > > > +++ b/security/integrity/evm/evm_crypto.c > > > @@ -144,7 +144,7 @@ static void hmac_add_misc(struct shash_desc *desc= , struct inode *inode, > > > char type, char *digest) > > > { > > > struct h_misc { > > > - unsigned long ino; > > > + u64 ino; > > > __u32 generation; > > > uid_t uid; > > > gid_t gid; > > >=20 > >=20 > > Agreed. > >=20 > > >=20 > > > That should make no material difference on 64-bit hosts. What's the > > > effect on 32-bit? Will they just need to remeasure everything or woul= d > > > the consequences be more dire? Do we have any clue whether anyone is > > > using EVM in 32-bit environments? > >=20 > > All good questions. Unfortunately I don't know the answer to most of th= em. What > > we do know: changing the size of the i_ino field would affect EVM file = metadata > > verification and would require relabeling the filesystem. Even package= s > > containing EVM portable signatures, which don't include or verify the i= _ino > > number, would be affected. > >=20 >=20 > Ouch. Technically, I guess this is ABI... >=20 > While converting to u64 seems like the ideal thing to do, the other > option might be to just keep this as an unsigned long for now. >=20 > No effect on 64-bit, but that could keep things working 32-bit when the > i_ino casts properly to a u32. ext4 would be fine since they don't > issue inode numbers larger than UINT_MAX. xfs and btrfs are a bit more > iffy, but worst case they'd just need to be relabeled (which is what > they'll need to do anyway). >=20 > If we do that, then we should probably add a comment to this function > explaining why it's an unsigned long. Agreed. >=20 > Thoughts? My concern would be embedded/IoT devices, but I don't have any insight into= who might be using it on 32 bit. Mimi