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Implement the unmap system call, writing back to the file if a page is dirty before removing from SPT

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sBubshait
2024-12-04 19:07:28 +00:00
parent 02b79d1934
commit ecbb4e74a5
3 changed files with 75 additions and 1 deletions
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33
src/userprog/syscall.c
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@@ -459,11 +459,42 @@ syscall_mmap (int fd, void *addr)
/* Handles the syscall for unmapping a memory mapped file.
Pre: mapping is a valid mapping identifier returned by mmap syscall.*/
Pre: mapping is a valid mapping identifier returned by mmap syscall. */
static void
syscall_munmap (mapid_t mapping)
{
/* Get the mmap entry from the mapping identifier. */
struct mmap_entry *mmap = mmap_get (mapping);
/* Free all the pages associated with the mapping, writing back to the file
if necessary. */
off_t length = file_length (mmap->file);
for (off_t ofs = 0; ofs < length; ofs += PGSIZE)
{
void *upage = mmap->upage + ofs;
/* Get the SPT page entry for this page. */
struct page_entry *page = page_get(upage);
if (page == NULL)
continue;
/* Write the page back to the file if it is dirty. */
if (pagedir_is_dirty (thread_current ()->pagedir, upage))
{
lock_acquire (&filesys_lock);
file_write_at (mmap->file, upage, page->read_bytes, ofs);
lock_release (&filesys_lock);
}
/* Remove the page from the supplemental page table. */
hash_delete (&thread_current ()->pages, &page->elem);
}
/* Remove the mapping from the mmap table. Close the file and free the mmap
entry. */
hash_delete (&thread_current ()->mmap_files, &mmap->elem);
file_close (mmap->file);
free(mmap);
}
/* Hashing function needed for the open_file table. Returns a hash for an entry,