git: 1ccbdf561f41 - main - tmpfs: Rework file handles
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Date: Mon, 23 Dec 2024 14:47:51 UTC
The branch main has been updated by olce: URL: https://cgit.FreeBSD.org/src/commit/?id=1ccbdf561f417f9fe802131d5b1756ac45fd314d commit 1ccbdf561f417f9fe802131d5b1756ac45fd314d Author: Olivier Certner <olce@FreeBSD.org> AuthorDate: 2024-12-06 20:23:59 +0000 Commit: Olivier Certner <olce@FreeBSD.org> CommitDate: 2024-12-23 14:46:55 +0000 tmpfs: Rework file handles Change 'struct tmpfs_fid_data' to behave consistently with the private structure other FSes use. In a nutshell, make it a full alias of 'struct fid', instead of just using it to fill 'fid_data'. This implies adding a length field at start (aliasing 'fid_len' of 'struct fid'), and filling 'fid_len' with the full size of the aliased structure. To ensure that the new 'struct tmpfs_fid_data' is smaller than 'struct fid', which the compile-time assert introduced in commit 91b5592a1e1af974 ("fs: Add static asserts for the size of fid structures") checks (and thus was not strong enough when added), use '__packed'. A consequence of this change is that copying the 'struct tmpfs_fid_data' into a stack-allocated variable becomes unnecessary, we simply rely on the compiler emitting the proper code on seeing '__packed' (and on the start of 'struct tmpfs_fid_data' being naturally aligned, which is normally guaranteed by kernel's malloc() and/or inclusion in 'struct fhandle'). Reviewed by: markj Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D47956 --- sys/fs/tmpfs/tmpfs.h | 5 ++--- sys/fs/tmpfs/tmpfs_vfsops.c | 16 ++++++---------- sys/fs/tmpfs/tmpfs_vnops.c | 16 ++++------------ 3 files changed, 12 insertions(+), 25 deletions(-) diff --git a/sys/fs/tmpfs/tmpfs.h b/sys/fs/tmpfs/tmpfs.h index 58f8720c3f84..52307cc7c7b2 100644 --- a/sys/fs/tmpfs/tmpfs.h +++ b/sys/fs/tmpfs/tmpfs.h @@ -448,11 +448,10 @@ struct tmpfs_mount { * NFS code. */ struct tmpfs_fid_data { + unsigned short tfd_len; ino_t tfd_id; unsigned long tfd_gen; -}; -_Static_assert(sizeof(struct tmpfs_fid_data) <= MAXFIDSZ, - "(struct tmpfs_fid_data) is larger than (struct fid).fid_data"); +} __packed; struct tmpfs_dir_cursor { struct tmpfs_dirent *tdc_current; diff --git a/sys/fs/tmpfs/tmpfs_vfsops.c b/sys/fs/tmpfs/tmpfs_vfsops.c index dd48a24dab2f..431893b77bb9 100644 --- a/sys/fs/tmpfs/tmpfs_vfsops.c +++ b/sys/fs/tmpfs/tmpfs_vfsops.c @@ -585,29 +585,25 @@ static int tmpfs_fhtovp(struct mount *mp, struct fid *fhp, int flags, struct vnode **vpp) { - struct tmpfs_fid_data tfd; + struct tmpfs_fid_data *tfd; struct tmpfs_mount *tmp; struct tmpfs_node *node; int error; - if (fhp->fid_len != sizeof(tfd)) + if (fhp->fid_len != sizeof(*tfd)) return (EINVAL); - /* - * Copy from fid_data onto the stack to avoid unaligned pointer use. - * See the comment in sys/mount.h on struct fid for details. - */ - memcpy(&tfd, fhp->fid_data, fhp->fid_len); + tfd = (struct tmpfs_fid_data *)fhp; tmp = VFS_TO_TMPFS(mp); - if (tfd.tfd_id >= tmp->tm_nodes_max) + if (tfd->tfd_id >= tmp->tm_nodes_max) return (EINVAL); TMPFS_LOCK(tmp); LIST_FOREACH(node, &tmp->tm_nodes_used, tn_entries) { - if (node->tn_id == tfd.tfd_id && - node->tn_gen == tfd.tfd_gen) { + if (node->tn_id == tfd->tfd_id && + node->tn_gen == tfd->tfd_gen) { tmpfs_ref_node(node); break; } diff --git a/sys/fs/tmpfs/tmpfs_vnops.c b/sys/fs/tmpfs/tmpfs_vnops.c index 162977b8abf7..83e43ec7ba13 100644 --- a/sys/fs/tmpfs/tmpfs_vnops.c +++ b/sys/fs/tmpfs/tmpfs_vnops.c @@ -1706,23 +1706,15 @@ vop_vptofh { }; */ { - struct tmpfs_fid_data tfd; + struct tmpfs_fid_data *const tfd = (struct tmpfs_fid_data *)ap->a_fhp; struct tmpfs_node *node; - struct fid *fhp; _Static_assert(sizeof(struct tmpfs_fid_data) <= sizeof(struct fid), "struct tmpfs_fid_data cannot be larger than struct fid"); node = VP_TO_TMPFS_NODE(ap->a_vp); - fhp = ap->a_fhp; - fhp->fid_len = sizeof(tfd); - - /* - * Copy into fid_data from the stack to avoid unaligned pointer use. - * See the comment in sys/mount.h on struct fid for details. - */ - tfd.tfd_id = node->tn_id; - tfd.tfd_gen = node->tn_gen; - memcpy(fhp->fid_data, &tfd, fhp->fid_len); + tfd->tfd_len = sizeof(*tfd); + tfd->tfd_gen = node->tn_gen; + tfd->tfd_id = node->tn_id; return (0); }