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![John Stultz](/assets/img/avatar_default.png)
Currently seqlocks and seqcounts don't support lockdep. After running across a seqcount related deadlock in the timekeeping code, I used a less-refined and more focused variant of this patch to narrow down the cause of the issue. This is a first-pass attempt to properly enable lockdep functionality on seqlocks and seqcounts. Since seqcounts are used in the vdso gettimeofday code, I've provided non-lockdep accessors for those needs. I've also handled one case where there were nested seqlock writers and there may be more edge cases. Comments and feedback would be appreciated! Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Li Zefan <lizefan@huawei.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: netdev@vger.kernel.org Link: http://lkml.kernel.org/r/1381186321-4906-3-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
483 lines
11 KiB
C
483 lines
11 KiB
C
/*
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* linux/mm/filemap_xip.c
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*
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* Copyright (C) 2005 IBM Corporation
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* Author: Carsten Otte <cotte@de.ibm.com>
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*
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* derived from linux/mm/filemap.c - Copyright (C) Linus Torvalds
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*
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*/
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include <linux/export.h>
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#include <linux/uio.h>
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#include <linux/rmap.h>
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#include <linux/mmu_notifier.h>
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#include <linux/sched.h>
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#include <linux/seqlock.h>
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#include <linux/mutex.h>
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#include <linux/gfp.h>
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#include <asm/tlbflush.h>
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#include <asm/io.h>
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/*
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* We do use our own empty page to avoid interference with other users
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* of ZERO_PAGE(), such as /dev/zero
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*/
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static DEFINE_MUTEX(xip_sparse_mutex);
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static seqcount_t xip_sparse_seq = SEQCNT_ZERO(xip_sparse_seq);
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static struct page *__xip_sparse_page;
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/* called under xip_sparse_mutex */
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static struct page *xip_sparse_page(void)
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{
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if (!__xip_sparse_page) {
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struct page *page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
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if (page)
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__xip_sparse_page = page;
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}
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return __xip_sparse_page;
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}
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/*
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* This is a file read routine for execute in place files, and uses
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* the mapping->a_ops->get_xip_mem() function for the actual low-level
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* stuff.
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*
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* Note the struct file* is not used at all. It may be NULL.
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*/
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static ssize_t
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do_xip_mapping_read(struct address_space *mapping,
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struct file_ra_state *_ra,
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struct file *filp,
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char __user *buf,
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size_t len,
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loff_t *ppos)
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{
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struct inode *inode = mapping->host;
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pgoff_t index, end_index;
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unsigned long offset;
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loff_t isize, pos;
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size_t copied = 0, error = 0;
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BUG_ON(!mapping->a_ops->get_xip_mem);
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pos = *ppos;
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index = pos >> PAGE_CACHE_SHIFT;
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offset = pos & ~PAGE_CACHE_MASK;
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isize = i_size_read(inode);
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if (!isize)
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goto out;
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end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
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do {
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unsigned long nr, left;
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void *xip_mem;
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unsigned long xip_pfn;
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int zero = 0;
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/* nr is the maximum number of bytes to copy from this page */
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nr = PAGE_CACHE_SIZE;
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if (index >= end_index) {
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if (index > end_index)
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goto out;
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nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
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if (nr <= offset) {
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goto out;
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}
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}
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nr = nr - offset;
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if (nr > len - copied)
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nr = len - copied;
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error = mapping->a_ops->get_xip_mem(mapping, index, 0,
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&xip_mem, &xip_pfn);
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if (unlikely(error)) {
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if (error == -ENODATA) {
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/* sparse */
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zero = 1;
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} else
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goto out;
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}
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/* If users can be writing to this page using arbitrary
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* virtual addresses, take care about potential aliasing
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* before reading the page on the kernel side.
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*/
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if (mapping_writably_mapped(mapping))
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/* address based flush */ ;
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/*
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* Ok, we have the mem, so now we can copy it to user space...
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*
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* The actor routine returns how many bytes were actually used..
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* NOTE! This may not be the same as how much of a user buffer
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* we filled up (we may be padding etc), so we can only update
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* "pos" here (the actor routine has to update the user buffer
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* pointers and the remaining count).
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*/
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if (!zero)
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left = __copy_to_user(buf+copied, xip_mem+offset, nr);
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else
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left = __clear_user(buf + copied, nr);
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if (left) {
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error = -EFAULT;
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goto out;
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}
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copied += (nr - left);
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offset += (nr - left);
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index += offset >> PAGE_CACHE_SHIFT;
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offset &= ~PAGE_CACHE_MASK;
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} while (copied < len);
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out:
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*ppos = pos + copied;
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if (filp)
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file_accessed(filp);
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return (copied ? copied : error);
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}
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ssize_t
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xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
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{
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if (!access_ok(VERIFY_WRITE, buf, len))
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return -EFAULT;
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return do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
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buf, len, ppos);
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}
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EXPORT_SYMBOL_GPL(xip_file_read);
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/*
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* __xip_unmap is invoked from xip_unmap and
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* xip_write
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*
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* This function walks all vmas of the address_space and unmaps the
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* __xip_sparse_page when found at pgoff.
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*/
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static void
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__xip_unmap (struct address_space * mapping,
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unsigned long pgoff)
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{
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struct vm_area_struct *vma;
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struct mm_struct *mm;
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unsigned long address;
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pte_t *pte;
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pte_t pteval;
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spinlock_t *ptl;
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struct page *page;
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unsigned count;
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int locked = 0;
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count = read_seqcount_begin(&xip_sparse_seq);
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page = __xip_sparse_page;
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if (!page)
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return;
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retry:
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mutex_lock(&mapping->i_mmap_mutex);
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vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
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mm = vma->vm_mm;
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address = vma->vm_start +
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((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
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BUG_ON(address < vma->vm_start || address >= vma->vm_end);
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pte = page_check_address(page, mm, address, &ptl, 1);
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if (pte) {
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/* Nuke the page table entry. */
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flush_cache_page(vma, address, pte_pfn(*pte));
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pteval = ptep_clear_flush(vma, address, pte);
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page_remove_rmap(page);
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dec_mm_counter(mm, MM_FILEPAGES);
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BUG_ON(pte_dirty(pteval));
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pte_unmap_unlock(pte, ptl);
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/* must invalidate_page _before_ freeing the page */
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mmu_notifier_invalidate_page(mm, address);
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page_cache_release(page);
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}
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}
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mutex_unlock(&mapping->i_mmap_mutex);
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if (locked) {
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mutex_unlock(&xip_sparse_mutex);
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} else if (read_seqcount_retry(&xip_sparse_seq, count)) {
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mutex_lock(&xip_sparse_mutex);
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locked = 1;
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goto retry;
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}
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}
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/*
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* xip_fault() is invoked via the vma operations vector for a
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* mapped memory region to read in file data during a page fault.
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*
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* This function is derived from filemap_fault, but used for execute in place
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*/
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static int xip_file_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
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{
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struct file *file = vma->vm_file;
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struct address_space *mapping = file->f_mapping;
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struct inode *inode = mapping->host;
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pgoff_t size;
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void *xip_mem;
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unsigned long xip_pfn;
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struct page *page;
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int error;
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/* XXX: are VM_FAULT_ codes OK? */
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again:
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size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
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if (vmf->pgoff >= size)
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return VM_FAULT_SIGBUS;
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error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
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&xip_mem, &xip_pfn);
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if (likely(!error))
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goto found;
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if (error != -ENODATA)
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return VM_FAULT_OOM;
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/* sparse block */
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if ((vma->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
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(vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) &&
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(!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
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int err;
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/* maybe shared writable, allocate new block */
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mutex_lock(&xip_sparse_mutex);
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error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1,
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&xip_mem, &xip_pfn);
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mutex_unlock(&xip_sparse_mutex);
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if (error)
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return VM_FAULT_SIGBUS;
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/* unmap sparse mappings at pgoff from all other vmas */
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__xip_unmap(mapping, vmf->pgoff);
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found:
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err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address,
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xip_pfn);
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if (err == -ENOMEM)
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return VM_FAULT_OOM;
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/*
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* err == -EBUSY is fine, we've raced against another thread
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* that faulted-in the same page
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*/
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if (err != -EBUSY)
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BUG_ON(err);
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return VM_FAULT_NOPAGE;
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} else {
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int err, ret = VM_FAULT_OOM;
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mutex_lock(&xip_sparse_mutex);
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write_seqcount_begin(&xip_sparse_seq);
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error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
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&xip_mem, &xip_pfn);
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if (unlikely(!error)) {
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write_seqcount_end(&xip_sparse_seq);
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mutex_unlock(&xip_sparse_mutex);
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goto again;
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}
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if (error != -ENODATA)
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goto out;
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/* not shared and writable, use xip_sparse_page() */
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page = xip_sparse_page();
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if (!page)
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goto out;
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err = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
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page);
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if (err == -ENOMEM)
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goto out;
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ret = VM_FAULT_NOPAGE;
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out:
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write_seqcount_end(&xip_sparse_seq);
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mutex_unlock(&xip_sparse_mutex);
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return ret;
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}
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}
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static const struct vm_operations_struct xip_file_vm_ops = {
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.fault = xip_file_fault,
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.page_mkwrite = filemap_page_mkwrite,
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.remap_pages = generic_file_remap_pages,
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};
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int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
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{
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BUG_ON(!file->f_mapping->a_ops->get_xip_mem);
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file_accessed(file);
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vma->vm_ops = &xip_file_vm_ops;
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vma->vm_flags |= VM_MIXEDMAP;
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return 0;
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}
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EXPORT_SYMBOL_GPL(xip_file_mmap);
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static ssize_t
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__xip_file_write(struct file *filp, const char __user *buf,
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size_t count, loff_t pos, loff_t *ppos)
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{
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struct address_space * mapping = filp->f_mapping;
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const struct address_space_operations *a_ops = mapping->a_ops;
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struct inode *inode = mapping->host;
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long status = 0;
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size_t bytes;
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ssize_t written = 0;
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BUG_ON(!mapping->a_ops->get_xip_mem);
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do {
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unsigned long index;
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unsigned long offset;
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size_t copied;
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void *xip_mem;
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unsigned long xip_pfn;
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offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
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index = pos >> PAGE_CACHE_SHIFT;
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bytes = PAGE_CACHE_SIZE - offset;
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if (bytes > count)
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bytes = count;
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status = a_ops->get_xip_mem(mapping, index, 0,
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&xip_mem, &xip_pfn);
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if (status == -ENODATA) {
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/* we allocate a new page unmap it */
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mutex_lock(&xip_sparse_mutex);
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status = a_ops->get_xip_mem(mapping, index, 1,
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&xip_mem, &xip_pfn);
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mutex_unlock(&xip_sparse_mutex);
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if (!status)
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/* unmap page at pgoff from all other vmas */
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__xip_unmap(mapping, index);
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}
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if (status)
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break;
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copied = bytes -
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__copy_from_user_nocache(xip_mem + offset, buf, bytes);
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if (likely(copied > 0)) {
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status = copied;
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if (status >= 0) {
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written += status;
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count -= status;
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pos += status;
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buf += status;
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}
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}
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if (unlikely(copied != bytes))
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if (status >= 0)
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status = -EFAULT;
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if (status < 0)
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break;
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} while (count);
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*ppos = pos;
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/*
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* No need to use i_size_read() here, the i_size
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* cannot change under us because we hold i_mutex.
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*/
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if (pos > inode->i_size) {
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i_size_write(inode, pos);
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mark_inode_dirty(inode);
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}
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return written ? written : status;
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}
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ssize_t
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xip_file_write(struct file *filp, const char __user *buf, size_t len,
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loff_t *ppos)
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{
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struct address_space *mapping = filp->f_mapping;
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struct inode *inode = mapping->host;
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size_t count;
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loff_t pos;
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ssize_t ret;
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mutex_lock(&inode->i_mutex);
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if (!access_ok(VERIFY_READ, buf, len)) {
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ret=-EFAULT;
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goto out_up;
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}
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pos = *ppos;
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count = len;
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/* We can write back this queue in page reclaim */
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current->backing_dev_info = mapping->backing_dev_info;
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ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
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if (ret)
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goto out_backing;
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if (count == 0)
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goto out_backing;
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ret = file_remove_suid(filp);
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if (ret)
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goto out_backing;
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ret = file_update_time(filp);
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if (ret)
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goto out_backing;
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ret = __xip_file_write (filp, buf, count, pos, ppos);
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out_backing:
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current->backing_dev_info = NULL;
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out_up:
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mutex_unlock(&inode->i_mutex);
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return ret;
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}
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EXPORT_SYMBOL_GPL(xip_file_write);
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/*
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* truncate a page used for execute in place
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* functionality is analog to block_truncate_page but does use get_xip_mem
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* to get the page instead of page cache
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*/
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int
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xip_truncate_page(struct address_space *mapping, loff_t from)
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{
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pgoff_t index = from >> PAGE_CACHE_SHIFT;
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unsigned offset = from & (PAGE_CACHE_SIZE-1);
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unsigned blocksize;
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unsigned length;
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void *xip_mem;
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unsigned long xip_pfn;
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int err;
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BUG_ON(!mapping->a_ops->get_xip_mem);
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blocksize = 1 << mapping->host->i_blkbits;
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length = offset & (blocksize - 1);
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/* Block boundary? Nothing to do */
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if (!length)
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return 0;
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length = blocksize - length;
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err = mapping->a_ops->get_xip_mem(mapping, index, 0,
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&xip_mem, &xip_pfn);
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if (unlikely(err)) {
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if (err == -ENODATA)
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/* Hole? No need to truncate */
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return 0;
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else
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return err;
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}
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memset(xip_mem + offset, 0, length);
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return 0;
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}
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EXPORT_SYMBOL_GPL(xip_truncate_page);
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