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authorWu Fengguang <fengguang.wu@intel.com>2009-06-16 15:33:17 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:45 -0700
commit84a892456046921a40646114deed65e2df93a1bc (patch)
tree2639b6031e55988b8780960c023618c381d61c55 /Documentation/sysctl/vm.txt
parent81236810226f71bd9ff77321c8e8276dae7efc61 (diff)
writeback: skip new or to-be-freed inodes
1) I_FREEING tests should be coupled with I_CLEAR The two I_FREEING tests are racy because clear_inode() can set i_state to I_CLEAR between the clear of I_SYNC and the test of I_FREEING. 2) skip I_WILL_FREE inodes in generic_sync_sb_inodes() to avoid possible races with generic_forget_inode() generic_forget_inode() sets I_WILL_FREE call writeback on its own, so generic_sync_sb_inodes() shall not try to step in and create possible races: generic_forget_inode inode->i_state |= I_WILL_FREE; spin_unlock(&inode_lock); generic_sync_sb_inodes() spin_lock(&inode_lock); __iget(inode); __writeback_single_inode // see non zero i_count may WARN here ==> WARN_ON(inode->i_state & I_WILL_FREE); spin_unlock(&inode_lock); may call generic_forget_inode again ==> iput(inode); The above race and warning didn't turn up because writeback_inodes() holds the s_umount lock, so generic_forget_inode() finds MS_ACTIVE and returns early. But we are not sure the UBIFS calls and future callers will guarantee that. So skip I_WILL_FREE inodes for the sake of safety. Cc: Eric Sandeen <sandeen@sandeen.net> Acked-by: Jeff Layton <jlayton@redhat.com> Cc: Masayoshi MIZUMA <m.mizuma@jp.fujitsu.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Christoph Hellwig <hch@infradead.org> Acked-by: Jan Kara <jack@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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