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Remove zpl_revalidate

This patch removes the need for zpl_revalidate altogether.

There were 3 main reasons why we used d_revalidate:

1. periodic automounted snapshots umount deferral
2. negative dentries created before snapshot rollback
3. stale inodes referenced by dentry cache after snapshot rollback

Periodic snapshots deferral solution introduces zfs_exit_fs function,
which is called as a part of ZFS_EXIT(zfsvfs_t) macro.

Negative dentries and stale inodes are solved by flushing the dcache
for the particular dataset on zfs_resume_fs call.

This patch also removes now unused HAVE_S_D_OP configure test.

Fixes #8774

Signed-off-by: Pavel Snajdr <snajpa@snajpa.net>
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snajpa committed Nov 4, 2019
1 parent 734de7c commit 286d2eba957321ef43071123740f4ed8c48eb840
@@ -150,37 +150,13 @@ AC_DEFUN([ZFS_AC_KERNEL_CONST_DENTRY_OPERATIONS], [
])
])

dnl #
dnl # 2.6.38 API change
dnl # Added sb->s_d_op default dentry_operations member
dnl #
AC_DEFUN([ZFS_AC_KERNEL_SRC_S_D_OP], [
ZFS_LINUX_TEST_SRC([super_block_s_d_op], [
#include <linux/fs.h>
],[
struct super_block sb __attribute__ ((unused));
sb.s_d_op = NULL;
])
])

AC_DEFUN([ZFS_AC_KERNEL_S_D_OP], [
AC_MSG_CHECKING([whether super_block has s_d_op])
ZFS_LINUX_TEST_RESULT([super_block_s_d_op], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_S_D_OP, 1, [struct super_block has s_d_op])
], [
AC_MSG_RESULT(no)
])
])

AC_DEFUN([ZFS_AC_KERNEL_SRC_DENTRY], [
ZFS_AC_KERNEL_SRC_D_MAKE_ROOT
ZFS_AC_KERNEL_SRC_D_OBTAIN_ALIAS
ZFS_AC_KERNEL_SRC_D_PRUNE_ALIASES
ZFS_AC_KERNEL_SRC_D_SET_D_OP
ZFS_AC_KERNEL_SRC_D_REVALIDATE_NAMEIDATA
ZFS_AC_KERNEL_SRC_CONST_DENTRY_OPERATIONS
ZFS_AC_KERNEL_SRC_S_D_OP
])

AC_DEFUN([ZFS_AC_KERNEL_DENTRY], [
@@ -190,5 +166,4 @@ AC_DEFUN([ZFS_AC_KERNEL_DENTRY], [
ZFS_AC_KERNEL_D_SET_D_OP
ZFS_AC_KERNEL_D_REVALIDATE_NAMEIDATA
ZFS_AC_KERNEL_CONST_DENTRY_OPERATIONS
ZFS_AC_KERNEL_S_D_OP
])
@@ -197,6 +197,7 @@ typedef struct zfid_long {
extern int zfs_suspend_fs(zfsvfs_t *zfsvfs);
extern int zfs_resume_fs(zfsvfs_t *zfsvfs, struct dsl_dataset *ds);
extern int zfs_end_fs(zfsvfs_t *zfsvfs, struct dsl_dataset *ds);
extern void zfs_exit_fs(zfsvfs_t *zfsvfs);
extern int zfs_userspace_one(zfsvfs_t *zfsvfs, zfs_userquota_prop_t type,
const char *domain, uint64_t rid, uint64_t *valuep);
extern int zfs_userspace_many(zfsvfs_t *zfsvfs, zfs_userquota_prop_t type,
@@ -84,6 +84,7 @@ do { \
/* Must be called before exiting the operation. */
#define ZFS_EXIT(zfsvfs) \
do { \
zfs_exit_fs(zfsvfs); \
rrm_exit(&(zfsvfs)->z_teardown_lock, FTAG); \
} while (0)
#define ZPL_EXIT(zfsvfs) ZFS_EXIT(zfsvfs)
@@ -45,7 +45,6 @@ extern const struct inode_operations zpl_inode_operations;
extern const struct inode_operations zpl_dir_inode_operations;
extern const struct inode_operations zpl_symlink_inode_operations;
extern const struct inode_operations zpl_special_inode_operations;
extern dentry_operations_t zpl_dentry_operations;

/* zpl_file.c */
extern ssize_t zpl_read_common(struct inode *ip, const char *buf,
@@ -1931,9 +1931,6 @@ zfs_domount(struct super_block *sb, zfs_mnt_t *zm, int silent)
sb->s_op = &zpl_super_operations;
sb->s_xattr = zpl_xattr_handlers;
sb->s_export_op = &zpl_export_operations;
#ifdef HAVE_S_D_OP
sb->s_d_op = &zpl_dentry_operations;
#endif /* HAVE_S_D_OP */

/* Set features for file system. */
zfs_set_fuid_feature(zfsvfs);
@@ -2303,6 +2300,16 @@ zfs_resume_fs(zfsvfs_t *zfsvfs, dsl_dataset_t *ds)
zfs_unlinked_drain(zfsvfs);
}

/*
* Most of the time zfs_suspend_fs is used for changing the contents
* of the underlying dataset. ZFS rollback and receive operations
* might create files for which negative dentries are present in
* the cache. Since walking the dcache would require a lot of GPL-only
* code duplication, it's much easier on these rather rare occasions
* just to flush the whole dcache for the given dataset/filesystem.
*/
shrink_dcache_sb(zfsvfs->z_sb);

bail:
if (err != 0)
zfsvfs->z_unmounted = B_TRUE;
@@ -2353,6 +2360,26 @@ zfs_end_fs(zfsvfs_t *zfsvfs, dsl_dataset_t *ds)
return (0);
}

/*
* Automounted snapshots rely on periodic revalidation
* to defer snapshots from being automatically unmounted.
*/

inline void
zfs_exit_fs(zfsvfs_t *zfsvfs)
{
if (!zfsvfs->z_issnap)
return;

if (time_after(jiffies, zfsvfs->z_snap_defer_time +
MAX(zfs_expire_snapshot * HZ / 2, HZ))) {
zfsvfs->z_snap_defer_time = jiffies;
zfsctl_snapshot_unmount_delay(zfsvfs->z_os->os_spa,
dmu_objset_id(zfsvfs->z_os),
zfs_expire_snapshot);
}
}

int
zfs_set_version(zfsvfs_t *zfsvfs, uint64_t newvers)
{
@@ -70,9 +70,6 @@ zpl_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)

spin_lock(&dentry->d_lock);
dentry->d_time = jiffies;
#ifndef HAVE_S_D_OP
d_set_d_op(dentry, &zpl_dentry_operations);
#endif /* HAVE_S_D_OP */
spin_unlock(&dentry->d_lock);

if (error) {
@@ -655,59 +652,6 @@ zpl_fallocate(struct inode *ip, int mode, loff_t offset, loff_t len)
}
#endif /* HAVE_INODE_FALLOCATE */

static int
#ifdef HAVE_D_REVALIDATE_NAMEIDATA
zpl_revalidate(struct dentry *dentry, struct nameidata *nd)
{
unsigned int flags = (nd ? nd->flags : 0);
#else
zpl_revalidate(struct dentry *dentry, unsigned int flags)
{
#endif /* HAVE_D_REVALIDATE_NAMEIDATA */
/* CSTYLED */
zfsvfs_t *zfsvfs = dentry->d_sb->s_fs_info;
int error;

if (flags & LOOKUP_RCU)
return (-ECHILD);

/*
* Automounted snapshots rely on periodic dentry revalidation
* to defer snapshots from being automatically unmounted.
*/
if (zfsvfs->z_issnap) {
if (time_after(jiffies, zfsvfs->z_snap_defer_time +
MAX(zfs_expire_snapshot * HZ / 2, HZ))) {
zfsvfs->z_snap_defer_time = jiffies;
zfsctl_snapshot_unmount_delay(zfsvfs->z_os->os_spa,
dmu_objset_id(zfsvfs->z_os), zfs_expire_snapshot);
}
}

/*
* After a rollback negative dentries created before the rollback
* time must be invalidated. Otherwise they can obscure files which
* are only present in the rolled back dataset.
*/
if (dentry->d_inode == NULL) {
spin_lock(&dentry->d_lock);
error = time_before(dentry->d_time, zfsvfs->z_rollback_time);
spin_unlock(&dentry->d_lock);

if (error)
return (0);
}

/*
* The dentry may reference a stale inode if a mounted file system
* was rolled back to a point in time where the object didn't exist.
*/
if (dentry->d_inode && ITOZ(dentry->d_inode)->z_is_stale)
return (0);

return (1);
}

const struct inode_operations zpl_inode_operations = {
.setattr = zpl_setattr,
.getattr = zpl_getattr,
@@ -820,7 +764,3 @@ const struct inode_operations zpl_special_inode_operations = {
#endif /* HAVE_GET_ACL | HAVE_CHECK_ACL | HAVE_PERMISSION */
#endif /* CONFIG_FS_POSIX_ACL */
};

dentry_operations_t zpl_dentry_operations = {
.d_revalidate = zpl_revalidate,
};

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