On Thu, Aug 24, 2023 at 08:02:25AM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Recently xfs/513 started failing on my test machines testing "-o
> ro,norecovery" mount options. This was being emitted in dmesg:
>
> [ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.
>
> Turns out, readonly mounts with the fsopen()/fsconfig() mount API
> have been busted since day zero. It's only taken 5 years for debian
> unstable to start using this "new" mount API, and shortly after this
> I noticed xfs/513 had started to fail as per above.
>
> The syscall trace is:
>
> fsopen("xfs", FSOPEN_CLOEXEC) = 3
> mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
> .....
> fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
> fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
> fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
> fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
> close(3) = 0
>
> Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
> what threw out the error.
>
> During mount instantiation, we call xfs_fs_validate_params() which
> does:
>
> /* No recovery flag requires a read-only mount */
> if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
> xfs_warn(mp, "no-recovery mounts must be read-only.");
> return -EINVAL;
> }
>
> and xfs_is_readonly() checks internal mount flags for read only
> state. This state is set in xfs_init_fs_context() from the
> context superblock flag state:
>
> /*
> * Copy binary VFS mount flags we are interested in.
> */
> if (fc->sb_flags & SB_RDONLY)
> set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);
>
> With the old mount API, all of the VFS specific superblock flags
> had already been parsed and set before xfs_init_fs_context() is
> called, so this all works fine.
>
> However, in the brave new fsopen/fsconfig world,
> xfs_init_fs_context() is called from fsopen() context, before any
> VFS superblock have been set or parsed. Hence if we use fsopen(),
> the internal XFS readonly state is *never set*. Hence anything that
> depends on xfs_is_readonly() actually returning true for read only
> mounts is broken if fsopen() has been used to mount the filesystem.
>
> Fix this by moving this internal state initialisation to
> xfs_fs_fill_super() before we attempt to validate the parameters
> that have been set prior to the FSCONFIG_CMD_CREATE call being made.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Huh. Wow. I would have expected to find /anything/ in fstests that
exercises the new mount api, but:
lax:~/cdev/work/fstests(0)> git grep -E '(fsconfig|fspick|fsopen)'
lax:~/cdev/work/fstests(1)>
What other weird things are lurking here?
Anyhow, I guess that's a side effect of xfs_mount mirroring some of the
vfs state flags, so....
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_super.c | 27 +++++++++++++++++----------
> 1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 09638e8fb4ee..8ca01510628b 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1509,6 +1509,18 @@ xfs_fs_fill_super(
>
> mp->m_super = sb;
>
> + /*
> + * Copy VFS mount flags from the context now that all parameter parsing
> + * is guaranteed to have been completed by either the old mount API or
> + * the newer fsopen/fsconfig API.
> + */
> + if (fc->sb_flags & SB_RDONLY)
> + set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);
> + if (fc->sb_flags & SB_DIRSYNC)
> + mp->m_features |= XFS_FEAT_DIRSYNC;
> + if (fc->sb_flags & SB_SYNCHRONOUS)
> + mp->m_features |= XFS_FEAT_WSYNC;
> +
> error = xfs_fs_validate_params(mp);
> if (error)
> goto out_free_names;
> @@ -1988,6 +2000,11 @@ static const struct fs_context_operations xfs_context_ops = {
> .free = xfs_fs_free,
> };
>
> +/*
> + * WARNING: do not initialise any parameters in this function that depend on
> + * mount option parsing having already been performed as this can be called from
> + * fsopen() before any parameters have been set.
> + */
> static int xfs_init_fs_context(
> struct fs_context *fc)
> {
> @@ -2019,16 +2036,6 @@ static int xfs_init_fs_context(
> mp->m_logbsize = -1;
> mp->m_allocsize_log = 16; /* 64k */
>
> - /*
> - * Copy binary VFS mount flags we are interested in.
> - */
> - if (fc->sb_flags & SB_RDONLY)
> - set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);
> - if (fc->sb_flags & SB_DIRSYNC)
> - mp->m_features |= XFS_FEAT_DIRSYNC;
> - if (fc->sb_flags & SB_SYNCHRONOUS)
> - mp->m_features |= XFS_FEAT_WSYNC;
> -
> fc->s_fs_info = mp;
> fc->ops = &xfs_context_ops;
>
> --
> 2.40.1
>
