trunc.c

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#include <core/system.h>
#include <fs/vfs.h>
#include <dev/dev.h>
#include <mm/vm.h>

int vfs_trunc(struct vnode *vnode, off_t len)
{
    vfs_log(LOG_DEBUG, "vfs_trunc(vnode=%p, len=%d)\n", vnode, len);
 
    /* invalid request */
    if (!vnode)
        return -EINVAL;
 
    /* a device node has no length to change */
    if (ISDEV(vnode))
        return -EINVAL;
 
    /* invalid request */
    if (!vnode->fs)
        return -EINVAL;
 
    /* the filesystem doesn't support it */
    if (!vnode->fs->vops.trunc)
        return -ENOSYS;
 
    off_t old = vnode->size;
    int err = vnode->fs->vops.trunc(vnode, len);
 
    /* refresh the file's pages in the page cache between the old end and
     * the new one */
    if (!err)
        vnode_pages_update(vnode, MIN(old, len), MAX(old, len));
 
    return err;
}