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autofs: don't bother with atomics for ino->count

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All writers are serialized on inode->i_rwsem.  So are the readers
outside of expire.c.  And the readers in expire.c are in the
code that really doesn't care about narrow races - it's looking
for expiry candidates and its callers have to cope with the
possibility of a good candidate becoming busy right under them.

No point bothering with atomic operations - just use int and
mark the non-serialized readers with READ_ONCE().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2019-09-17 23:31:27 -04:00
parent c3aed16680
commit 850d71acd5
3 changed files with 14 additions and 14 deletions
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2
fs/autofs/autofs_i.h
View File

@ -63,7 +63,7 @@ struct autofs_info {
struct autofs_sb_info *sbi;
unsigned long last_used;
atomic_t count;
int count;
kuid_t uid;
kgid_t gid;

6
fs/autofs/expire.c
View File

@ -211,7 +211,7 @@ static int autofs_tree_busy(struct vfsmount *mnt,
}
} else {
struct autofs_info *ino = autofs_dentry_ino(p);
unsigned int ino_count = atomic_read(&ino->count);
unsigned int ino_count = READ_ONCE(ino->count);
/* allow for dget above and top is already dgot */
if (p == top)
@ -379,7 +379,7 @@ static struct dentry *should_expire(struct dentry *dentry,
/* Not a forced expire? */
if (!(how & AUTOFS_EXP_FORCED)) {
/* ref-walk currently on this dentry? */
ino_count = atomic_read(&ino->count) + 1;
ino_count = READ_ONCE(ino->count) + 1;
if (d_count(dentry) > ino_count)
return NULL;
}
@ -396,7 +396,7 @@ static struct dentry *should_expire(struct dentry *dentry,
/* Not a forced expire? */
if (!(how & AUTOFS_EXP_FORCED)) {
/* ref-walk currently on this dentry? */
ino_count = atomic_read(&ino->count) + 1;
ino_count = READ_ONCE(ino->count) + 1;
if (d_count(dentry) > ino_count)
return NULL;
}

20
fs/autofs/root.c
View File

@ -569,9 +569,9 @@ static int autofs_dir_symlink(struct inode *dir,
d_add(dentry, inode);
dget(dentry);
atomic_inc(&ino->count);
ino->count++;
p_ino = autofs_dentry_ino(dentry->d_parent);
atomic_inc(&p_ino->count);
p_ino->count++;
dir->i_mtime = current_time(dir);
@ -609,9 +609,9 @@ static int autofs_dir_unlink(struct inode *dir, struct dentry *dentry)
if (sbi->flags & AUTOFS_SBI_CATATONIC)
return -EACCES;
atomic_dec(&ino->count);
ino->count--;
p_ino = autofs_dentry_ino(dentry->d_parent);
atomic_dec(&p_ino->count);
p_ino->count--;
dput(ino->dentry);
d_inode(dentry)->i_size = 0;
@ -669,7 +669,7 @@ static void autofs_clear_leaf_automount_flags(struct dentry *dentry)
/* only consider parents below dentrys in the root */
if (IS_ROOT(parent->d_parent))
return;
if (atomic_read(&autofs_dentry_ino(parent)->count) == 2)
if (autofs_dentry_ino(parent)->count == 2)
managed_dentry_set_managed(parent);
}
@ -691,7 +691,7 @@ static int autofs_dir_rmdir(struct inode *dir, struct dentry *dentry)
if (sbi->flags & AUTOFS_SBI_CATATONIC)
return -EACCES;
if (atomic_read(&ino->count) != 1)
if (ino->count != 1)
return -ENOTEMPTY;
spin_lock(&sbi->lookup_lock);
@ -702,9 +702,9 @@ static int autofs_dir_rmdir(struct inode *dir, struct dentry *dentry)
if (sbi->version < 5)
autofs_clear_leaf_automount_flags(dentry);
atomic_dec(&ino->count);
ino->count--;
p_ino = autofs_dentry_ino(dentry->d_parent);
atomic_dec(&p_ino->count);
p_ino->count--;
dput(ino->dentry);
d_inode(dentry)->i_size = 0;
clear_nlink(d_inode(dentry));
@ -750,9 +750,9 @@ static int autofs_dir_mkdir(struct inode *dir,
autofs_set_leaf_automount_flags(dentry);
dget(dentry);
atomic_inc(&ino->count);
ino->count++;
p_ino = autofs_dentry_ino(dentry->d_parent);
atomic_inc(&p_ino->count);
p_ino->count++;
inc_nlink(dir);
dir->i_mtime = current_time(dir);