Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull second vfs pile from Al Viro:
 "The stuff in there: fsfreeze deadlock fixes by Jan (essentially, the
  deadlock reproduced by xfstests 068), symlink and hardlink restriction
  patches, plus assorted cleanups and fixes.

  Note that another fsfreeze deadlock (emergency thaw one) is *not*
  dealt with - the series by Fernando conflicts a lot with Jan's, breaks
  userland ABI (FIFREEZE semantics gets changed) and trades the deadlock
  for massive vfsmount leak; this is going to be handled next cycle.
  There probably will be another pull request, but that stuff won't be
  in it."

Fix up trivial conflicts due to unrelated changes next to each other in
drivers/{staging/gdm72xx/usb_boot.c, usb/gadget/storage_common.c}

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (54 commits)
  delousing target_core_file a bit
  Documentation: Correct s_umount state for freeze_fs/unfreeze_fs
  fs: Remove old freezing mechanism
  ext2: Implement freezing
  btrfs: Convert to new freezing mechanism
  nilfs2: Convert to new freezing mechanism
  ntfs: Convert to new freezing mechanism
  fuse: Convert to new freezing mechanism
  gfs2: Convert to new freezing mechanism
  ocfs2: Convert to new freezing mechanism
  xfs: Convert to new freezing code
  ext4: Convert to new freezing mechanism
  fs: Protect write paths by sb_start_write - sb_end_write
  fs: Skip atime update on frozen filesystem
  fs: Add freezing handling to mnt_want_write() / mnt_drop_write()
  fs: Improve filesystem freezing handling
  switch the protection of percpu_counter list to spinlock
  nfsd: Push mnt_want_write() outside of i_mutex
  btrfs: Push mnt_want_write() outside of i_mutex
  fat: Push mnt_want_write() outside of i_mutex
  ...

1 files changed, 10 insertions, 18 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index c7062c896d7c..9f6d2e41281d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2306,8 +2306,8 @@ EXPORT_SYMBOL(block_commit_write);
  * beyond EOF, then the page is guaranteed safe against truncation until we
  * unlock the page.
  *
- * Direct callers of this function should call vfs_check_frozen() so that page
- * fault does not busyloop until the fs is thawed.
+ * Direct callers of this function should protect against filesystem freezing
+ * using sb_start_write() - sb_end_write() functions.
  */
 int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
                          get_block_t get_block)
@@ -2318,6 +2318,12 @@ int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
         loff_t size;
         int ret;
 
+        /*
+         * Update file times before taking page lock. We may end up failing the
+         * fault so this update may be superfluous but who really cares...
+         */
+        file_update_time(vma->vm_file);
+
         lock_page(page);
         size = i_size_read(inode);
         if ((page->mapping != inode->i_mapping) ||
@@ -2339,18 +2345,7 @@ int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 
         if (unlikely(ret < 0))
                 goto out_unlock;
-        /*
-         * Freezing in progress? We check after the page is marked dirty and
-         * with page lock held so if the test here fails, we are sure freezing
-         * code will wait during syncing until the page fault is done - at that
-         * point page will be dirty and unlocked so freezing code will write it
-         * and writeprotect it again.
-         */
         set_page_dirty(page);
-        if (inode->i_sb->s_frozen != SB_UNFROZEN) {
-                ret = -EAGAIN;
-                goto out_unlock;
-        }
         wait_on_page_writeback(page);
         return 0;
 out_unlock:
@@ -2365,12 +2360,9 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
         int ret;
         struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
 
-        /*
-         * This check is racy but catches the common case. The check in
-         * __block_page_mkwrite() is reliable.
-         */
-        vfs_check_frozen(sb, SB_FREEZE_WRITE);
+        sb_start_pagefault(sb);
         ret = __block_page_mkwrite(vma, vmf, get_block);
+        sb_end_pagefault(sb);
         return block_page_mkwrite_return(ret);
 }
 EXPORT_SYMBOL(block_page_mkwrite);