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[PATCH] fix deadlock in ext2

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Fix a deadlock possible in the ext2 file system implementation.  This
deadlock occurs when a file is removed from an ext2 file system which was
mounted with the "sync" mount option.

The problem is that ext2_xattr_delete_inode() was invoking the routine,
sync_dirty_buffer(), using a buffer head which was previously locked via
lock_buffer().  The first thing that sync_dirty_buffer() does is to lock
the buffer head that it was passed.  It does this via lock_buffer().  Oops.

The solution is to unlock the buffer head in ext2_xattr_delete_inode()
before invoking sync_dirty_buffer().  This makes the code in
ext2_xattr_delete_inode() obey the same locking rules as all other callers
of sync_dirty_buffer() in the ext2 file system implementation.

Signed-off-by: Peter Staubach <staubach@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Peter Staubach 2006-02-17 13:52:36 -08:00 committed by Linus Torvalds
parent 614f8f50ca
commit b2f49033d8
1 changed files with 4 additions and 2 deletions
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6
fs/ext2/xattr.c
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@ -792,18 +792,20 @@ ext2_xattr_delete_inode(struct inode *inode)
ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1); ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
get_bh(bh); get_bh(bh);
bforget(bh); bforget(bh);
unlock_buffer(bh);
} else { } else {
HDR(bh)->h_refcount = cpu_to_le32( HDR(bh)->h_refcount = cpu_to_le32(
le32_to_cpu(HDR(bh)->h_refcount) - 1); le32_to_cpu(HDR(bh)->h_refcount) - 1);
if (ce) if (ce)
mb_cache_entry_release(ce); mb_cache_entry_release(ce);
ea_bdebug(bh, "refcount now=%d",
le32_to_cpu(HDR(bh)->h_refcount));
unlock_buffer(bh);
mark_buffer_dirty(bh); mark_buffer_dirty(bh);
if (IS_SYNC(inode)) if (IS_SYNC(inode))
sync_dirty_buffer(bh); sync_dirty_buffer(bh);
DQUOT_FREE_BLOCK(inode, 1); DQUOT_FREE_BLOCK(inode, 1);
} }
ea_bdebug(bh, "refcount now=%d", le32_to_cpu(HDR(bh)->h_refcount) - 1);
unlock_buffer(bh);
EXT2_I(inode)->i_file_acl = 0; EXT2_I(inode)->i_file_acl = 0;
cleanup: cleanup: