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>
diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
index 1c08fef..92dabdc 100644
--- a/fs/ntfs/attrib.c
+++ b/fs/ntfs/attrib.c
@@ -1,7 +1,7 @@
/**
* attrib.c - NTFS attribute operations. Part of the Linux-NTFS project.
*
- * Copyright (c) 2001-2006 Anton Altaparmakov
+ * Copyright (c) 2001-2007 Anton Altaparmakov
* Copyright (c) 2002 Richard Russon
*
* This program/include file is free software; you can redistribute it and/or
@@ -2500,7 +2500,7 @@
struct page *page;
u8 *kaddr;
pgoff_t idx, end;
- unsigned int start_ofs, end_ofs, size;
+ unsigned start_ofs, end_ofs, size;
ntfs_debug("Entering for ofs 0x%llx, cnt 0x%llx, val 0x%hx.",
(long long)ofs, (long long)cnt, val);
@@ -2548,6 +2548,8 @@
kunmap_atomic(kaddr, KM_USER0);
set_page_dirty(page);
page_cache_release(page);
+ balance_dirty_pages_ratelimited(mapping);
+ cond_resched();
if (idx == end)
goto done;
idx++;
@@ -2604,6 +2606,8 @@
kunmap_atomic(kaddr, KM_USER0);
set_page_dirty(page);
page_cache_release(page);
+ balance_dirty_pages_ratelimited(mapping);
+ cond_resched();
}
done:
ntfs_debug("Done.");