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-rw-r--r--fs/libfs.c158
1 files changed, 86 insertions, 72 deletions
diff --git a/fs/libfs.c b/fs/libfs.c
index be57e64834e5..03f831e77c6d 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -86,47 +86,60 @@ int dcache_dir_close(struct inode *inode, struct file *file)
EXPORT_SYMBOL(dcache_dir_close);
/* parent is locked at least shared */
-/*
- * Returns an element of siblings' list.
- * We are looking for <count>th positive after <p>; if
- * found, dentry is grabbed and passed to caller via *<res>.
- * If no such element exists, the anchor of list is returned
- * and *<res> is set to NULL.
- */
-static struct list_head *scan_positives(struct dentry *cursor,
- struct list_head *p,
- loff_t count,
- struct dentry **res)
+static struct dentry *next_positive(struct dentry *parent,
+ struct list_head *from,
+ int count)
{
- struct dentry *dentry = cursor->d_parent, *found = NULL;
+ unsigned *seq = &parent->d_inode->__i_dir_seq, n;
+ struct dentry *res;
+ struct list_head *p;
+ bool skipped;
+ int i;
- spin_lock(&dentry->d_lock);
- while ((p = p->next) != &dentry->d_subdirs) {
+retry:
+ i = count;
+ skipped = false;
+ n = smp_load_acquire(seq) & ~1;
+ res = NULL;
+ rcu_read_lock();
+ for (p = from->next; p != &parent->d_subdirs; p = p->next) {
struct dentry *d = list_entry(p, struct dentry, d_child);
- // we must at least skip cursors, to avoid livelocks
- if (d->d_flags & DCACHE_DENTRY_CURSOR)
- continue;
- if (simple_positive(d) && !--count) {
- spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
- if (simple_positive(d))
- found = dget_dlock(d);
- spin_unlock(&d->d_lock);
- if (likely(found))
- break;
- count = 1;
- }
- if (need_resched()) {
- list_move(&cursor->d_child, p);
- p = &cursor->d_child;
- spin_unlock(&dentry->d_lock);
- cond_resched();
- spin_lock(&dentry->d_lock);
+ if (!simple_positive(d)) {
+ skipped = true;
+ } else if (!--i) {
+ res = d;
+ break;
}
}
- spin_unlock(&dentry->d_lock);
- dput(*res);
- *res = found;
- return p;
+ rcu_read_unlock();
+ if (skipped) {
+ smp_rmb();
+ if (unlikely(*seq != n))
+ goto retry;
+ }
+ return res;
+}
+
+static void move_cursor(struct dentry *cursor, struct list_head *after)
+{
+ struct dentry *parent = cursor->d_parent;
+ unsigned n, *seq = &parent->d_inode->__i_dir_seq;
+ spin_lock(&parent->d_lock);
+ preempt_disable_rt();
+ for (;;) {
+ n = *seq;
+ if (!(n & 1) && cmpxchg(seq, n, n + 1) == n)
+ break;
+ cpu_relax();
+ }
+ __list_del(cursor->d_child.prev, cursor->d_child.next);
+ if (after)
+ list_add(&cursor->d_child, after);
+ else
+ list_add_tail(&cursor->d_child, &parent->d_subdirs);
+ smp_store_release(seq, n + 2);
+ preempt_enable_rt();
+ spin_unlock(&parent->d_lock);
}
loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
@@ -142,28 +155,17 @@ loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
return -EINVAL;
}
if (offset != file->f_pos) {
- struct dentry *cursor = file->private_data;
- struct dentry *to = NULL;
- struct list_head *p;
-
file->f_pos = offset;
- inode_lock_shared(dentry->d_inode);
-
- if (file->f_pos > 2) {
- p = scan_positives(cursor, &dentry->d_subdirs,
- file->f_pos - 2, &to);
- spin_lock(&dentry->d_lock);
- list_move(&cursor->d_child, p);
- spin_unlock(&dentry->d_lock);
- } else {
- spin_lock(&dentry->d_lock);
- list_del_init(&cursor->d_child);
- spin_unlock(&dentry->d_lock);
+ if (file->f_pos >= 2) {
+ struct dentry *cursor = file->private_data;
+ struct dentry *to;
+ loff_t n = file->f_pos - 2;
+
+ inode_lock_shared(dentry->d_inode);
+ to = next_positive(dentry, &dentry->d_subdirs, n);
+ move_cursor(cursor, to ? &to->d_child : NULL);
+ inode_unlock_shared(dentry->d_inode);
}
-
- dput(to);
-
- inode_unlock_shared(dentry->d_inode);
}
return offset;
}
@@ -185,29 +187,25 @@ int dcache_readdir(struct file *file, struct dir_context *ctx)
{
struct dentry *dentry = file->f_path.dentry;
struct dentry *cursor = file->private_data;
- struct list_head *anchor = &dentry->d_subdirs;
- struct dentry *next = NULL;
- struct list_head *p;
+ struct list_head *p = &cursor->d_child;
+ struct dentry *next;
+ bool moved = false;
if (!dir_emit_dots(file, ctx))
return 0;
if (ctx->pos == 2)
- p = anchor;
- else
- p = &cursor->d_child;
-
- while ((p = scan_positives(cursor, p, 1, &next)) != anchor) {
+ p = &dentry->d_subdirs;
+ while ((next = next_positive(dentry, p, 1)) != NULL) {
if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
d_inode(next)->i_ino, dt_type(d_inode(next))))
break;
+ moved = true;
+ p = &next->d_child;
ctx->pos++;
}
- spin_lock(&dentry->d_lock);
- list_move_tail(&cursor->d_child, p);
- spin_unlock(&dentry->d_lock);
- dput(next);
-
+ if (moved)
+ move_cursor(cursor, p);
return 0;
}
EXPORT_SYMBOL(dcache_readdir);
@@ -864,8 +862,8 @@ out:
EXPORT_SYMBOL_GPL(simple_attr_read);
/* interpret the buffer as a number to call the set function with */
-ssize_t simple_attr_write(struct file *file, const char __user *buf,
- size_t len, loff_t *ppos)
+static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos, bool is_signed)
{
struct simple_attr *attr;
unsigned long long val;
@@ -886,7 +884,10 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
goto out;
attr->set_buf[size] = '\0';
- ret = kstrtoull(attr->set_buf, 0, &val);
+ if (is_signed)
+ ret = kstrtoll(attr->set_buf, 0, &val);
+ else
+ ret = kstrtoull(attr->set_buf, 0, &val);
if (ret)
goto out;
ret = attr->set(attr->data, val);
@@ -896,8 +897,21 @@ out:
mutex_unlock(&attr->mutex);
return ret;
}
+
+ssize_t simple_attr_write(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ return simple_attr_write_xsigned(file, buf, len, ppos, false);
+}
EXPORT_SYMBOL_GPL(simple_attr_write);
+ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ return simple_attr_write_xsigned(file, buf, len, ppos, true);
+}
+EXPORT_SYMBOL_GPL(simple_attr_write_signed);
+
/**
* generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
* @sb: filesystem to do the file handle conversion on
generated by cgit 1.2.3-korg (git 2.39.0) at 2024-05-02 11:10:59 +0000