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dcache_{readdir,dir_lseek}(): don't bother with nested ->d_lock 

Make sure that directory is locked shared in dcache_dir_lseek();
for dcache_readdir() it's already tru, and that's enough to make
simple_positive() stable.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-06-06 18:55:57 -04:00
parent e7d6ef9790
commit 274f5b041d
1 changed files with 3 additions and 9 deletions
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12
fs/libfs.c
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@ -103,6 +103,7 @@ loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
struct dentry *cursor = file->private_data;
loff_t n = file->f_pos - 2;
inode_lock_shared(dentry->d_inode);
spin_lock(&dentry->d_lock);
/* d_lock not required for cursor */
list_del(&cursor->d_child);
@ -110,14 +111,13 @@ loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
while (n && p != &dentry->d_subdirs) {
struct dentry *next;
next = list_entry(p, struct dentry, d_child);
spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
if (simple_positive(next))
n--;
spin_unlock(&next->d_lock);
p = p->next;
}
list_add_tail(&cursor->d_child, p);
spin_unlock(&dentry->d_lock);
inode_unlock_shared(dentry->d_inode);
}
}
return offset;
@ -150,22 +150,16 @@ int dcache_readdir(struct file *file, struct dir_context *ctx)
for (p = q->next; p != &dentry->d_subdirs; p = p->next) {
struct dentry *next = list_entry(p, struct dentry, d_child);
spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
if (!simple_positive(next)) {
spin_unlock(&next->d_lock);
if (!simple_positive(next))
continue;
}
spin_unlock(&next->d_lock);
spin_unlock(&dentry->d_lock);
if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
d_inode(next)->i_ino, dt_type(d_inode(next))))
return 0;
spin_lock(&dentry->d_lock);
spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
/* next is still alive */
list_move(q, p);
spin_unlock(&next->d_lock);
p = q;
ctx->pos++;
}