On Thu, Dec 03, 2020 at 10:27:24AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> When we allocate a new inode, we often need to add an attribute to
> the inode as part of the create. This can happen as a result of
> needing to add default ACLs or security labels before the inode is
> made visible to userspace.
>
> This is highly inefficient right now. We do the create transaction
> to allocate the inode, then we do an "add attr fork" transaction to
> modify the just created empty inode to set the inode fork offset to
> allow attributes to be stored, then we go and do the attribute
> creation.
>
> This means 3 transactions instead of 1 to allocate an inode, and
> this greatly increases the load on the CIL commit code, resulting in
> excessive contention on the CIL spin locks and performance
> degradation:
>
> 18.99% [kernel] [k] __pv_queued_spin_lock_slowpath
> 3.57% [kernel] [k] do_raw_spin_lock
> 2.51% [kernel] [k] __raw_callee_save___pv_queued_spin_unlock
> 2.48% [kernel] [k] memcpy
> 2.34% [kernel] [k] xfs_log_commit_cil
>
> The typical profile resulting from running fsmark on a selinux enabled
> filesytem is adds this overhead to the create path:
>
> - 15.30% xfs_init_security
> - 15.23% security_inode_init_security
> - 13.05% xfs_initxattrs
> - 12.94% xfs_attr_set
> - 6.75% xfs_bmap_add_attrfork
> - 5.51% xfs_trans_commit
> - 5.48% __xfs_trans_commit
> - 5.35% xfs_log_commit_cil
> - 3.86% _raw_spin_lock
> - do_raw_spin_lock
> __pv_queued_spin_lock_slowpath
> - 0.70% xfs_trans_alloc
> 0.52% xfs_trans_reserve
> - 5.41% xfs_attr_set_args
> - 5.39% xfs_attr_set_shortform.constprop.0
> - 4.46% xfs_trans_commit
> - 4.46% __xfs_trans_commit
> - 4.33% xfs_log_commit_cil
> - 2.74% _raw_spin_lock
> - do_raw_spin_lock
> __pv_queued_spin_lock_slowpath
> 0.60% xfs_inode_item_format
> 0.90% xfs_attr_try_sf_addname
> - 1.99% selinux_inode_init_security
> - 1.02% security_sid_to_context_force
> - 1.00% security_sid_to_context_core
> - 0.92% sidtab_entry_to_string
> - 0.90% sidtab_sid2str_get
> 0.59% sidtab_sid2str_put.part.0
> - 0.82% selinux_determine_inode_label
> - 0.77% security_transition_sid
> 0.70% security_compute_sid.part.0
>
> And fsmark creation rate performance drops by ~25%. The key point to
> note here is that half the additional overhead comes from adding the
> attribute fork to the newly created inode. That's crazy, considering
> we can do this same thing at inode create time with a couple of
> lines of code and no extra overhead.
>
> So, if we know we are going to add an attribute immediately after
> creating the inode, let's just initialise the attribute fork inside
> the create transaction and chop that whole chunk of code out of
> the create fast path. This completely removes the performance
> drop caused by enabling SELinux, and the profile looks like:
>
> - 8.99% xfs_init_security
> - 9.00% security_inode_init_security
> - 6.43% xfs_initxattrs
> - 6.37% xfs_attr_set
> - 5.45% xfs_attr_set_args
> - 5.42% xfs_attr_set_shortform.constprop.0
> - 4.51% xfs_trans_commit
> - 4.54% __xfs_trans_commit
> - 4.59% xfs_log_commit_cil
> - 2.67% _raw_spin_lock
> - 3.28% do_raw_spin_lock
> 3.08% __pv_queued_spin_lock_slowpath
> 0.66% xfs_inode_item_format
> - 0.90% xfs_attr_try_sf_addname
> - 0.60% xfs_trans_alloc
> - 2.35% selinux_inode_init_security
> - 1.25% security_sid_to_context_force
> - 1.21% security_sid_to_context_core
> - 1.19% sidtab_entry_to_string
> - 1.20% sidtab_sid2str_get
> - 0.86% sidtab_sid2str_put.part.0
> - 0.62% _raw_spin_lock_irqsave
> - 0.77% do_raw_spin_lock
> __pv_queued_spin_lock_slowpath
> - 0.84% selinux_determine_inode_label
> - 0.83% security_transition_sid
> 0.86% security_compute_sid.part.0
>
> Which indicates the XFS overhead of creating the selinux xattr has
> been halved. This doesn't fix the CIL lock contention problem, just
> means it's not a limiting factor for this workload. Lock contention
> in the security subsystems is going to be an issue soon, though...
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_inode_fork.c | 20 +++++++++++++++-----
> fs/xfs/libxfs/xfs_inode_fork.h | 1 +
> fs/xfs/xfs_inode.c | 24 ++++++++++++++++++++----
> fs/xfs/xfs_inode.h | 5 +++--
> fs/xfs/xfs_iops.c | 10 +++++++++-
> fs/xfs/xfs_qm.c | 2 +-
> fs/xfs/xfs_symlink.c | 2 +-
> 7 files changed, 50 insertions(+), 14 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> index 7575de5cecb1..5d5b466bd787 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.c
> +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> @@ -280,6 +280,19 @@ xfs_dfork_attr_shortform_size(
> return be16_to_cpu(atp->hdr.totsize);
> }
>
> +struct xfs_ifork *
> +xfs_ifork_alloc(
> + int8_t format,
enum xfs_dinode_fmt format, ?
> + xfs_extnum_t nextents)
> +{
> + struct xfs_ifork *ifp;
> +
> + ifp = kmem_cache_zalloc(xfs_ifork_zone, GFP_NOFS | __GFP_NOFAIL);
> + ifp->if_format = format;
> + ifp->if_nextents = nextents;
> + return ifp;
> +}
> +
> int
> xfs_iformat_attr_fork(
> struct xfs_inode *ip,
> @@ -291,11 +304,8 @@ xfs_iformat_attr_fork(
> * Initialize the extent count early, as the per-format routines may
> * depend on it.
> */
> - ip->i_afp = kmem_cache_zalloc(xfs_ifork_zone, GFP_NOFS | __GFP_NOFAIL);
> - ip->i_afp->if_format = dip->di_aformat;
> - if (unlikely(ip->i_afp->if_format == 0)) /* pre IRIX 6.2 file system */
> - ip->i_afp->if_format = XFS_DINODE_FMT_EXTENTS;
Can we still mount an irix 6.1 filesystem? I would guess not, but
removing old cruft is a separate patch. Granted you did say RFC...
> - ip->i_afp->if_nextents = be16_to_cpu(dip->di_anextents);
> + ip->i_afp = xfs_ifork_alloc(dip->di_aformat,
> + be16_to_cpu(dip->di_anextents));
>
> switch (ip->i_afp->if_format) {
> case XFS_DINODE_FMT_LOCAL:
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index a4953e95c4f3..3ad088c6a9d2 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -80,6 +80,7 @@ static inline int8_t xfs_ifork_format(struct xfs_ifork *ifp)
> return ifp->if_format;
> }
>
> +struct xfs_ifork *xfs_ifork_alloc(int8_t format, xfs_extnum_t nextents);
> struct xfs_ifork *xfs_iext_state_to_fork(struct xfs_inode *ip, int state);
>
> int xfs_iformat_data_fork(struct xfs_inode *, struct xfs_dinode *);
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 2bfbcf28b1bd..9ee2e0b4c6fd 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -800,6 +800,7 @@ xfs_ialloc(
> dev_t rdev,
> prid_t prid,
> xfs_buf_t **ialloc_context,
> + bool init_attrs,
init_xattrs ? Just to distinguish them from regular file attrs like
mode/size/owner/etc.
> xfs_inode_t **ipp)
> {
> struct xfs_mount *mp = tp->t_mountp;
> @@ -918,6 +919,18 @@ xfs_ialloc(
> ASSERT(0);
> }
>
> + /*
> + * If we need to create attributes immediately after allocating the
> + * inode, initialise an empty attribute fork right now. We use the
> + * default fork offset for attributes here as we don't know exactly what
> + * size or how many attributes we might be adding. We can do this safely
> + * here because we know the data fork is completely empty right now.
> + */
> + if (init_attrs) {
> + ip->i_afp = xfs_ifork_alloc(XFS_DINODE_FMT_EXTENTS, 0);
> + ip->i_d.di_forkoff = xfs_default_attroffset(ip) >> 3;
> + }
> +
> /*
> * Log the new values stuffed into the inode.
> */
> @@ -951,6 +964,7 @@ xfs_dir_ialloc(
> xfs_nlink_t nlink,
> dev_t rdev,
> prid_t prid, /* project id */
> + bool init_attrs,
> xfs_inode_t **ipp) /* pointer to inode; it will be
> locked. */
> {
> @@ -980,7 +994,7 @@ xfs_dir_ialloc(
> * the inode(s) that we've just allocated.
> */
> code = xfs_ialloc(tp, dp, mode, nlink, rdev, prid, &ialloc_context,
> - &ip);
> + init_attrs, &ip);
>
> /*
> * Return an error if we were unable to allocate a new inode.
> @@ -1050,7 +1064,7 @@ xfs_dir_ialloc(
> * this call should always succeed.
> */
> code = xfs_ialloc(tp, dp, mode, nlink, rdev, prid,
> - &ialloc_context, &ip);
> + &ialloc_context, init_attrs, &ip);
>
> /*
> * If we get an error at this point, return to the caller
> @@ -1112,6 +1126,7 @@ xfs_create(
> struct xfs_name *name,
> umode_t mode,
> dev_t rdev,
> + bool init_attrs,
> xfs_inode_t **ipp)
> {
> int is_dir = S_ISDIR(mode);
> @@ -1182,7 +1197,8 @@ xfs_create(
> * entry pointing to them, but a directory also the "." entry
> * pointing to itself.
> */
> - error = xfs_dir_ialloc(&tp, dp, mode, is_dir ? 2 : 1, rdev, prid, &ip);
> + error = xfs_dir_ialloc(&tp, dp, mode, is_dir ? 2 : 1, rdev, prid,
> + init_attrs, &ip);
> if (error)
> goto out_trans_cancel;
>
> @@ -1304,7 +1320,7 @@ xfs_create_tmpfile(
> if (error)
> goto out_trans_cancel;
>
> - error = xfs_dir_ialloc(&tp, dp, mode, 0, 0, prid, &ip);
> + error = xfs_dir_ialloc(&tp, dp, mode, 0, 0, prid, false, &ip);
> if (error)
> goto out_trans_cancel;
>
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index 751a3d1d7d84..670dfab334de 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -370,7 +370,8 @@ void xfs_inactive(struct xfs_inode *ip);
> int xfs_lookup(struct xfs_inode *dp, struct xfs_name *name,
> struct xfs_inode **ipp, struct xfs_name *ci_name);
> int xfs_create(struct xfs_inode *dp, struct xfs_name *name,
> - umode_t mode, dev_t rdev, struct xfs_inode **ipp);
> + umode_t mode, dev_t rdev, bool need_xattr,
> + struct xfs_inode **ipp);
> int xfs_create_tmpfile(struct xfs_inode *dp, umode_t mode,
> struct xfs_inode **ipp);
> int xfs_remove(struct xfs_inode *dp, struct xfs_name *name,
> @@ -408,7 +409,7 @@ xfs_extlen_t xfs_get_extsz_hint(struct xfs_inode *ip);
> xfs_extlen_t xfs_get_cowextsz_hint(struct xfs_inode *ip);
>
> int xfs_dir_ialloc(struct xfs_trans **, struct xfs_inode *, umode_t,
> - xfs_nlink_t, dev_t, prid_t,
> + xfs_nlink_t, dev_t, prid_t, bool need_xattr,
> struct xfs_inode **);
>
> static inline int
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 1414ab79eacf..75b44b82ad1f 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -126,6 +126,7 @@ xfs_cleanup_inode(
> xfs_remove(XFS_I(dir), &teardown, XFS_I(inode));
> }
>
> +
> STATIC int
> xfs_generic_create(
> struct inode *dir,
> @@ -161,7 +162,14 @@ xfs_generic_create(
> goto out_free_acl;
>
> if (!tmpfile) {
> - error = xfs_create(XFS_I(dir), &name, mode, rdev, &ip);
> + bool need_xattr = false;
> +
> + if ((IS_ENABLED(CONFIG_SECURITY) && dir->i_sb->s_security) ||
> + default_acl || acl)
> + need_xattr = true;
This should be a separate predicate in case the logic gets more twisty
later.
> +
> + error = xfs_create(XFS_I(dir), &name, mode, rdev,
> + need_xattr, &ip);
> } else {
> error = xfs_create_tmpfile(XFS_I(dir), mode, &ip);
/me bets O_TMPFILE files can have xattr-based security labels applied to
them too, right?
> }
> diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
> index b2a9abee8b2b..45faddfb4234 100644
> --- a/fs/xfs/xfs_qm.c
> +++ b/fs/xfs/xfs_qm.c
> @@ -787,7 +787,7 @@ xfs_qm_qino_alloc(
> return error;
>
> if (need_alloc) {
> - error = xfs_dir_ialloc(&tp, NULL, S_IFREG, 1, 0, 0, ip);
> + error = xfs_dir_ialloc(&tp, NULL, S_IFREG, 1, 0, 0, false, ip);
> if (error) {
> xfs_trans_cancel(tp);
> return error;
> diff --git a/fs/xfs/xfs_symlink.c b/fs/xfs/xfs_symlink.c
> index 8e88a7ca387e..20919aaea981 100644
> --- a/fs/xfs/xfs_symlink.c
> +++ b/fs/xfs/xfs_symlink.c
> @@ -224,7 +224,7 @@ xfs_symlink(
> * Allocate an inode for the symlink.
> */
> error = xfs_dir_ialloc(&tp, dp, S_IFLNK | (mode & ~S_IFMT), 1, 0,
> - prid, &ip);
> + prid, false, &ip);
> if (error)
> goto out_trans_cancel;
>
> --
> 2.28.0
>
