[RFC][PATCH 03/10] fs: Introduce i_count()

From: Peter Zijlstra
Date: Fri Feb 24 2017 - 13:45:01 EST

A preparatory patch; encapsulate i_count reading, modeled after
d_count().

There are a few sites around the kernel that look at i_count and base
decsions on it, some look OK, some really flaky:

- spufs:
i_count == 1, no i_lock

- ext4_free_inode:
i_count == 0, OK because super_operations::evict_inode

- writeback_single_inode:
i_count || I_WILL_FREE, seems OK

- hpfs_write_inode: no clue

- fsnotify_unmount_inodes:
i_count == 0, seem OK, we hold i_lock.
find_inode_fast() is serialized with i_lock
futex uses inc_not_zero().

- btrfs_invalidate_inodes:
checks for >1 i_count, while holding one, seems racy, nothing
(obviously) stops another reference from happening. Might be
fine in that any further reference cannot be an alias,
definitely needs a comment.

- check_conflicting_open: no clue

- maybe_indirect_to_direct: no clue

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/powerpc/platforms/cell/spufs/file.c | 2 +-
drivers/staging/lustre/lustre/llite/vvp_object.c | 2 +-
fs/btrfs/inode.c | 2 +-
fs/ceph/mds_client.c | 2 +-
fs/cifs/inode.c | 2 +-
fs/ext4/ialloc.c | 4 ++--
fs/fs-writeback.c | 2 +-
fs/hpfs/inode.c | 2 +-
fs/inode.c | 11 ++++++-----
fs/locks.c | 2 +-
fs/nfs/inode.c | 4 ++--
fs/notify/inode_mark.c | 2 +-
fs/orangefs/namei.c | 4 ++--
fs/reiserfs/stree.c | 2 +-
fs/ubifs/super.c | 2 +-
fs/xfs/xfs_trace.h | 2 +-
include/linux/fs.h | 5 +++++
include/trace/events/filelock.h | 2 +-
18 files changed, 30 insertions(+), 24 deletions(-)

--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -1492,7 +1492,7 @@ static int spufs_mfc_open(struct inode *
if (ctx->owner != current->mm)
return -EINVAL;

- if (atomic_read(&inode->i_count) != 1)
+ if (i_count(inode) != 1) /* XXX */
return -EBUSY;

mutex_lock(&ctx->mapping_lock);
--- a/drivers/staging/lustre/lustre/llite/vvp_object.c
+++ b/drivers/staging/lustre/lustre/llite/vvp_object.c
@@ -72,7 +72,7 @@ static int vvp_object_print(const struct
lli = ll_i2info(inode);
(*p)(env, cookie, "%lu/%u %o %u %d %p "DFID,
inode->i_ino, inode->i_generation, inode->i_mode,
- inode->i_nlink, atomic_read(&inode->i_count),
+ inode->i_nlink, i_count(inode),
lli->lli_clob, PFID(&lli->lli_fid));
}
return 0;
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5616,7 +5616,7 @@ void btrfs_invalidate_inodes(struct btrf
inode = igrab(&entry->vfs_inode);
if (inode) {
spin_unlock(&root->inode_lock);
- if (atomic_read(&inode->i_count) > 1)
+ if (i_count(inode) > 1)
d_prune_aliases(inode);
/*
* btrfs_drop_inode will have it removed from
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1448,7 +1448,7 @@ static int trim_caps_cb(struct inode *in
spin_unlock(&ci->i_ceph_lock);
d_prune_aliases(inode);
dout("trim_caps_cb %p cap %p pruned, count now %d\n",
- inode, cap, atomic_read(&inode->i_count));
+ inode, cap, i_count(inode));
return 0;
}

--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1950,7 +1950,7 @@ int cifs_revalidate_dentry_attr(struct d
}

cifs_dbg(FYI, "Update attributes: %s inode 0x%p count %d dentry: 0x%p d_time %ld jiffies %ld\n",
- full_path, inode, inode->i_count.counter,
+ full_path, inode, i_count(inode),
dentry, cifs_get_time(dentry), jiffies);

if (cifs_sb_master_tcon(CIFS_SB(sb))->unix_ext)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -270,10 +270,10 @@ void ext4_free_inode(handle_t *handle, s
"nonexistent device\n", __func__, __LINE__);
return;
}
- if (atomic_read(&inode->i_count) > 1) {
+ if (i_count(inode)) {
ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: count=%d",
__func__, __LINE__, inode->i_ino,
- atomic_read(&inode->i_count));
+ i_count(inode));
return;
}
if (inode->i_nlink) {
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1384,7 +1384,7 @@ static int writeback_single_inode(struct
int ret = 0;

spin_lock(&inode->i_lock);
- if (!atomic_read(&inode->i_count))
+ if (!i_count(inode))
WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
else
WARN_ON(inode->i_state & I_WILL_FREE);
--- a/fs/hpfs/inode.c
+++ b/fs/hpfs/inode.c
@@ -183,7 +183,7 @@ void hpfs_write_inode(struct inode *i)
struct hpfs_inode_info *hpfs_inode = hpfs_i(i);
struct inode *parent;
if (i->i_ino == hpfs_sb(i->i_sb)->sb_root) return;
- if (hpfs_inode->i_rddir_off && !atomic_read(&i->i_count)) {
+ if (hpfs_inode->i_rddir_off && !i_count(i)) { /* XXX */
if (*hpfs_inode->i_rddir_off)
pr_err("write_inode: some position still there\n");
kfree(hpfs_inode->i_rddir_off);
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -411,9 +411,10 @@ static void inode_lru_list_add(struct in
void inode_add_lru(struct inode *inode)
{
lockdep_assert_held(&inode->i_lock);
+
if (!(inode->i_state & (I_DIRTY_ALL | I_SYNC |
I_FREEING | I_WILL_FREE)) &&
- !atomic_read(&inode->i_count) && inode->i_sb->s_flags & MS_ACTIVE)
+ !i_count(inode) && inode->i_sb->s_flags & MS_ACTIVE)
inode_lru_list_add(inode);
}

@@ -605,7 +606,7 @@ void evict_inodes(struct super_block *sb
spin_lock(&sb->s_inode_list_lock);
list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
spin_lock(&inode->i_lock);
- if (atomic_read(&inode->i_count)) {
+ if (i_count(inode)) {
spin_unlock(&inode->i_lock);
continue;
}
@@ -665,7 +666,7 @@ int invalidate_inodes(struct super_block
busy = 1;
continue;
}
- if (atomic_read(&inode->i_count)) {
+ if (i_count(inode)) {
spin_unlock(&inode->i_lock);
busy = 1;
continue;
@@ -713,9 +714,9 @@ static enum lru_status inode_lru_isolate

/*
* Referenced or dirty inodes are still in use. Give them another pass
- * through the LRU as we canot reclaim them now.
+ * through the LRU as we cannot reclaim them now.
*/
- if (atomic_read(&inode->i_count) ||
+ if (i_count(inode) ||
(inode->i_state & ~I_REFERENCED)) {
list_lru_isolate(lru, &inode->i_lru);
spin_unlock(&inode->i_lock);
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1651,7 +1651,7 @@ check_conflicting_open(const struct dent
return -EAGAIN;

if ((arg == F_WRLCK) && ((d_count(dentry) > 1) ||
- (atomic_read(&inode->i_count) > 1)))
+ (i_count(inode) > 1)))
ret = -EAGAIN;

return ret;
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -531,7 +531,7 @@ nfs_fhget(struct super_block *sb, struct
inode->i_sb->s_id,
(unsigned long long)NFS_FILEID(inode),
nfs_display_fhandle_hash(fh),
- atomic_read(&inode->i_count));
+ i_count(inode));

out:
return inode;
@@ -1696,7 +1696,7 @@ static int nfs_update_inode(struct inode
dfprintk(VFS, "NFS: %s(%s/%lu fh_crc=0x%08x ct=%d info=0x%x)\n",
__func__, inode->i_sb->s_id, inode->i_ino,
nfs_display_fhandle_hash(NFS_FH(inode)),
- atomic_read(&inode->i_count), fattr->valid);
+ i_count(inode), fattr->valid);

if (!nfs_fileid_valid(nfsi, fattr)) {
printk(KERN_ERR "NFS: server %s error: fileid changed\n"
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -171,7 +171,7 @@ void fsnotify_unmount_inodes(struct supe
* evict all inodes with zero i_count from icache which is
* unnecessarily violent and may in fact be illegal to do.
*/
- if (!atomic_read(&inode->i_count)) {
+ if (!i_count(inode)) {
spin_unlock(&inode->i_lock);
continue;
}
--- a/fs/orangefs/namei.c
+++ b/fs/orangefs/namei.c
@@ -202,14 +202,14 @@ static struct dentry *orangefs_lookup(st
__func__,
__LINE__,
inode->i_ino,
- (int)atomic_read(&inode->i_count));
+ (int)i_count(inode));

/* update dentry/inode pair into dcache */
res = d_splice_alias(inode, dentry);

gossip_debug(GOSSIP_NAME_DEBUG,
"Lookup success (inode ct = %d)\n",
- (int)atomic_read(&inode->i_count));
+ (int)i_count(inode));
out:
op_release(new_op);
return res;
--- a/fs/reiserfs/stree.c
+++ b/fs/reiserfs/stree.c
@@ -1555,7 +1555,7 @@ static int maybe_indirect_to_direct(stru
* reading in the last block. The user will hit problems trying to
* read the file, but for now we just skip the indirect2direct
*/
- if (atomic_read(&inode->i_count) > 1 ||
+ if (i_count(inode) > 1 || /* XXX */
!tail_has_to_be_packed(inode) ||
!page || (REISERFS_I(inode)->i_flags & i_nopack_mask)) {
/* leave tail in an unformatted node */
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -349,7 +349,7 @@ static void ubifs_evict_inode(struct ino
goto out;

dbg_gen("inode %lu, mode %#x", inode->i_ino, (int)inode->i_mode);
- ubifs_assert(!atomic_read(&inode->i_count));
+ ubifs_assert(!i_count(inode));

truncate_inode_pages_final(&inode->i_data);

--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -704,7 +704,7 @@ DECLARE_EVENT_CLASS(xfs_iref_class,
TP_fast_assign(
__entry->dev = VFS_I(ip)->i_sb->s_dev;
__entry->ino = ip->i_ino;
- __entry->count = atomic_read(&VFS_I(ip)->i_count);
+ __entry->count = i_count(VFS_I(ip));
__entry->pincount = atomic_read(&ip->i_pincount);
__entry->caller_ip = caller_ip;
),
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2711,6 +2711,11 @@ static inline void lockdep_annotate_inod
extern void unlock_new_inode(struct inode *);
extern unsigned int get_next_ino(void);

+static inline int i_count(struct inode *inode)
+{
+ return atomic_read(&inode->i_count);
+}
+
extern void __iget(struct inode * inode);
extern void iget_failed(struct inode *);
extern void clear_inode(struct inode *);
--- a/include/trace/events/filelock.h
+++ b/include/trace/events/filelock.h
@@ -185,7 +185,7 @@ TRACE_EVENT(generic_add_lease,
__entry->i_ino = inode->i_ino;
__entry->wcount = atomic_read(&inode->i_writecount);
__entry->dcount = d_count(fl->fl_file->f_path.dentry);
- __entry->icount = atomic_read(&inode->i_count);
+ __entry->icount = i_count(inode);
__entry->fl_owner = fl ? fl->fl_owner : NULL;
__entry->fl_flags = fl ? fl->fl_flags : 0;
__entry->fl_type = fl ? fl->fl_type : 0;