dentry_utils.cpp

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// SPDX-License-Identifier: GPL-3.0-or-later
 
#include "mos/filesystem/dentry.hpp"
#include "mos/filesystem/inode.hpp"
#include "mos/filesystem/mount.hpp"
#include "mos/filesystem/vfs.hpp"
#include "mos/filesystem/vfs_types.hpp"
#include "mos/syslog/printk.hpp"
 
#include <mos_stdio.hpp>
#include <mos_stdlib.hpp>
#include <mos_string.hpp>
 
using namespace mos::string_literals;
 
dentry_t *dentry_ref(dentry_t *dentry)
{
    MOS_ASSERT(dentry);
    MOS_ASSERT(dentry->inode); // one cannot refcount a dentry without an inode
    dentry->refcount++;
    inode_ref(dentry->inode);
    pr_dinfo2(dcache_ref, "dentry %p '%s' increased refcount to %zu", (void *) dentry, dentry_name(dentry).c_str(), dentry->refcount.load());
    return dentry;
}
 
dentry_t *dentry_ref_up_to(dentry_t *dentry, dentry_t *root)
{
    pr_dinfo2(dcache_ref, "dentry_ref_up_to(%p '%s', %p '%s')", (void *) dentry, dentry_name(dentry).c_str(), (void *) root, dentry_name(root).c_str());
    for (dentry_t *cur = dentry; cur != root; cur = dentry_parent(*cur))
    {
        dentry_ref(cur);
        if (cur->name.empty())
        {
            cur = dentry_root_get_mountpoint(cur);
            dentry_ref(cur);
        }
    }
 
    dentry_ref(root); // it wasn't refcounted in the loop
 
    pr_dinfo2(dcache_ref, "...done");
    return dentry;
}

__nodiscard bool dentry_unref_one_norelease(dentry_t *dentry)
{
    if (dentry == NULL)
        return false;
 
    if (dentry->refcount == 0)
    {
        mos_warn("dentry refcount is already 0");
        return false;
    }
 
    dentry->refcount--;
 
    if (dentry->inode)
    {
        if (inode_unref(dentry->inode))
        {
            pr_dinfo2(vfs, "inode %p has no more references, releasing", (void *) dentry->inode);
            dentry->inode = NULL;
        }
    }
 
    pr_dinfo2(dcache_ref, "dentry %p '%s' decreased refcount to %zu", (void *) dentry, dentry_name(dentry).c_str(), dentry->refcount.load());
 
    if (dentry->name.empty() && dentry != root_dentry)
    {
        dentry_t *mountpoint = dentry_root_get_mountpoint(dentry);
        if (!mountpoint)
            goto done;
        mountpoint->refcount--;
        pr_dinfo2(dcache_ref, "  mountpoint %p '%s' decreased mountpoint refcount to %zu", (void *) mountpoint, dentry_name(mountpoint).c_str(),
                  mountpoint->refcount.load());
    }
done:
    return true;
}
 
void dentry_dump_refstat(const dentry_t *dentry, dump_refstat_receiver_t *receiver, void *receiver_data)
{
    if (dentry == NULL)
        return;
    static int depth = 0;
 
    receiver(depth, dentry, false, receiver_data);
 
    if (dentry->is_mountpoint)
    {
        dentry = dentry_get_mount(dentry)->root;
        receiver(depth, dentry, true, receiver_data);
    }
 
    depth++;
    tree_foreach_child(dentry_t, child, dentry)
    {
        dentry_dump_refstat(child, receiver, receiver_data);
    }
    depth--;
}
 
void dentry_check_refstat(const dentry_t *dentry)
{
    size_t expected_refcount = 0;
 
    if (dentry != root_dentry)
    {
        if (dentry->is_mountpoint)
            expected_refcount++; // the mountpoint itself
 
        if (dentry->name.empty())
            expected_refcount++; // the mounted root dentry
    }
    else
    {
        expected_refcount++; // the root dentry should only has one reference
    }
 
    tree_foreach_child(dentry_t, child, dentry)
    {
        expected_refcount += child->refcount;
    }
 
    if (dentry->refcount < expected_refcount)
    {
        mos_warn("dentry %p refcount %zu is less than expected refcount %zu", (void *) dentry, dentry->refcount.load(), expected_refcount);
        tree_foreach_child(dentry_t, child, dentry)
        {
            pr_warn("  child %p '%s' has %zu references", (void *) child, dentry_name(child).c_str(), child->refcount.load());
        }
        mos_panic("don't know how to handle this");
    }
    else if (dentry->refcount - expected_refcount)
    {
        pr_dinfo2(dcache_ref, "  dentry %p '%s' has %zu direct references", (void *) dentry, dentry_name(dentry).c_str(), dentry->refcount - expected_refcount);
    }
}
 
void dentry_try_release(dentry_t *dentry)
{
    MOS_ASSERT(dentry->refcount == 0);
 
    const bool can_release = dentry->inode == NULL && list_is_empty(&tree_node(dentry)->children);
    if (can_release)
    {
        list_remove(&dentry->tree_node);
        delete dentry;
    }
}
 
void dentry_unref(dentry_t *dentry)
{
    if (!dentry_unref_one_norelease(dentry))
        return;
 
    dentry_check_refstat(dentry);
    dentry_unref(dentry_parent(*dentry));
 
    if (dentry->refcount == 0)
        dentry_try_release(dentry);
}
 
std::optional<mos::string> dentry_path(const dentry_t *dentry, dentry_t *root)
{
    if (dentry == NULL)
        return std::nullopt;
 
    if (dentry == root)
        return "/";
 
    if (dentry->name.empty())
        dentry = dentry_root_get_mountpoint(dentry);
 
    auto path = dentry->name;
 
    for (dentry_t *current = dentry_parent(*dentry); current != root; current = dentry_parent(*current))
    {
        if (current->name.empty())
            current = dentry_root_get_mountpoint(current);
 
        // root for other fs trees (memfd, etc.)
        if (current == NULL)
            return ":/" + path;
        else
            path = current->name + "/" + path;
    }
 
    return "/" + path;
}