NTFS: Fix a mount time deadlock.

Big thanks go to Mathias Kolehmainen for reporting the bug, providing
debug output and testing the patches I sent him to get it working.

The fix was to stop calling ntfs_attr_set() at mount time as that causes
balance_dirty_pages_ratelimited() to be called which on systems with
little memory actually tries to go and balance the dirty pages which tries
to take the s_umount semaphore but because we are still in fill_super()
across which the VFS holds s_umount for writing this results in a
deadlock.

We now do the dirty work by hand by submitting individual buffers.  This
has the annoying "feature" that mounting can take a few seconds if the
journal is large as we have clear it all.  One day someone should improve
on this by deferring the journal clearing to a helper kernel thread so it
can be done in the background but I don't have time for this at the moment
and the current solution works fine so I am leaving it like this for now.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 19 deletions

diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index ffcc504a1667..c814204d4ea0 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1,7 +1,7 @@
 /*
  * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
  *
- * Copyright (c) 2001-2006 Anton Altaparmakov
+ * Copyright (c) 2001-2007 Anton Altaparmakov
  *
  * This program/include file is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as published
@@ -26,7 +26,6 @@
 #include <linux/swap.h>
 #include <linux/uio.h>
 #include <linux/writeback.h>
-#include <linux/sched.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -362,7 +361,7 @@ static inline void ntfs_fault_in_pages_readable(const char __user *uaddr,
         volatile char c;
 
         /* Set @end to the first byte outside the last page we care about. */
-        end = (const char __user*)PAGE_ALIGN((ptrdiff_t __user)uaddr + bytes);
+        end = (const char __user*)PAGE_ALIGN((unsigned long)uaddr + bytes);
 
         while (!__get_user(c, uaddr) && (uaddr += PAGE_SIZE, uaddr < end))
                 ;
@@ -532,7 +531,8 @@ static int ntfs_prepare_pages_for_non_resident_write(struct page **pages,
         blocksize_bits = vol->sb->s_blocksize_bits;
         u = 0;
         do {
-                struct page *page = pages[u];
+                page = pages[u];
+                BUG_ON(!page);
                 /*
                  * create_empty_buffers() will create uptodate/dirty buffers if
                  * the page is uptodate/dirty.
@@ -1291,7 +1291,7 @@ static inline size_t ntfs_copy_from_user(struct page **pages,
                 size_t bytes)
 {
         struct page **last_page = pages + nr_pages;
-        char *kaddr;
+        char *addr;
         size_t total = 0;
         unsigned len;
         int left;
@@ -1300,13 +1300,13 @@ static inline size_t ntfs_copy_from_user(struct page **pages,
                 len = PAGE_CACHE_SIZE - ofs;
                 if (len > bytes)
                         len = bytes;
-                kaddr = kmap_atomic(*pages, KM_USER0);
-                left = __copy_from_user_inatomic(kaddr + ofs, buf, len);
-                kunmap_atomic(kaddr, KM_USER0);
+                addr = kmap_atomic(*pages, KM_USER0);
+                left = __copy_from_user_inatomic(addr + ofs, buf, len);
+                kunmap_atomic(addr, KM_USER0);
                 if (unlikely(left)) {
                         /* Do it the slow way. */
-                        kaddr = kmap(*pages);
-                        left = __copy_from_user(kaddr + ofs, buf, len);
+                        addr = kmap(*pages);
+                        left = __copy_from_user(addr + ofs, buf, len);
                         kunmap(*pages);
                         if (unlikely(left))
                                 goto err_out;
@@ -1408,26 +1408,26 @@ static inline size_t ntfs_copy_from_user_iovec(struct page **pages,
                 size_t *iov_ofs, size_t bytes)
 {
         struct page **last_page = pages + nr_pages;
-        char *kaddr;
+        char *addr;
         size_t copied, len, total = 0;
 
         do {
                 len = PAGE_CACHE_SIZE - ofs;
                 if (len > bytes)
                         len = bytes;
-                kaddr = kmap_atomic(*pages, KM_USER0);
-                copied = __ntfs_copy_from_user_iovec_inatomic(kaddr + ofs,
+                addr = kmap_atomic(*pages, KM_USER0);
+                copied = __ntfs_copy_from_user_iovec_inatomic(addr + ofs,
                                 *iov, *iov_ofs, len);
-                kunmap_atomic(kaddr, KM_USER0);
+                kunmap_atomic(addr, KM_USER0);
                 if (unlikely(copied != len)) {
                         /* Do it the slow way. */
-                        kaddr = kmap(*pages);
-                        copied = __ntfs_copy_from_user_iovec_inatomic(kaddr + ofs,
+                        addr = kmap(*pages);
+                        copied = __ntfs_copy_from_user_iovec_inatomic(addr + ofs,
                                         *iov, *iov_ofs, len);
                         /*
                          * Zero the rest of the target like __copy_from_user().
                          */
-                        memset(kaddr + ofs + copied, 0, len - copied);
+                        memset(addr + ofs + copied, 0, len - copied);
                         kunmap(*pages);
                         if (unlikely(copied != len))
                                 goto err_out;
@@ -1735,8 +1735,6 @@ static int ntfs_commit_pages_after_write(struct page **pages,
         read_unlock_irqrestore(&ni->size_lock, flags);
         BUG_ON(initialized_size != i_size);
         if (end > initialized_size) {
-                unsigned long flags;
-
                 write_lock_irqsave(&ni->size_lock, flags);
                 ni->initialized_size = end;
                 i_size_write(vi, end);