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NTFS: Fix a mount time deadlock.

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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>
This commit is contained in:
Anton Altaparmakov 2007-10-12 09:37:15 +01:00 • committed by Linus Torvalds
parent f26e51f67a
commit bfab36e816
9 changed files with 181 additions and 53 deletions
Download patch file Download diff file Expand all files Collapse all files

8
fs/ntfs/attrib.c
View file

@ -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 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
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 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
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 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
kunmap_atomic(kaddr, KM_USER0);
set_page_dirty(page);
page_cache_release(page);
balance_dirty_pages_ratelimited(mapping);
cond_resched();
}
done:
ntfs_debug("Done.");