kernel/git/stable/linux.git/fs/fs-writeback.c, branch linux-2.6.29.y

fs: remove incorrect I_NEW warnings

2009-07-02T23:40:34+00:00

commit 545b9fd3d737afc0bb5203b1e79194a471605acd upstream. Some filesystems can call in to sync an inode that is still in the I_NEW state (eg. ext family, when mounted with -osync). This is OK because the filesystem has sole access to the new inode, so it can modify i_state without races (because no other thread should be modifying it, by definition of I_NEW). Ie. a false positive, so remove the warnings. The races are described here 7ef0d7377cb287e08f3ae94cebc919448e1f5dff, which is also where the warnings were introduced. Reported-by: Stephen Hemminger Signed-off-by: Nick Piggin Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

vfs: skip I_CLEAR state inodes

2009-04-27T17:36:55+00:00

upstream commit: b6fac63cc1f52ec27f29fe6c6c8494a2ffac33fd clear_inode() will switch inode state from I_FREEING to I_CLEAR, and do so _outside_ of inode_lock. So any I_FREEING testing is incomplete without a coupled testing of I_CLEAR. So add I_CLEAR tests to drop_pagecache_sb(), generic_sync_sb_inodes() and add_dquot_ref(). Masayoshi MIZUMA discovered the bug in drop_pagecache_sb() and Jan Kara reminds fixing the other two cases. Masayoshi MIZUMA has a nice panic flow: ===================================================================== [process A] | [process B] | | | prune_icache() | drop_pagecache() | spin_lock(&inode_lock) | drop_pagecache_sb() | inode->i_state |= I_FREEING; | | | spin_unlock(&inode_lock) | V | | | spin_lock(&inode_lock) | V | | | dispose_list() | | | list_del() | | | clear_inode() | | | inode->i_state = I_CLEAR | | | | | V | | | if (inode->i_state & (I_FREEING|I_WILL_FREE)) | | | continue; <==== NOT MATCH | | | | | | (DANGER from here on! Accessing disposing inode!) | | | | | | __iget() | | | list_move() <===== PANIC on poisoned list !! V V | (time) ===================================================================== Reported-by: Masayoshi MIZUMA Reviewed-by: Jan Kara Signed-off-by: Wu Fengguang Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [chrisw: backport to 2.6.29] Signed-off-by: Chris Wright

fs: new inode i_state corruption fix

2009-03-12T23:20:24+00:00

There was a report of a data corruption http://lkml.org/lkml/2008/11/14/121. There is a script included to reproduce the problem. During testing, I encountered a number of strange things with ext3, so I tried ext2 to attempt to reduce complexity of the problem. I found that fsstress would quickly hang in wait_on_inode, waiting for I_LOCK to be cleared, even though instrumentation showed that unlock_new_inode had already been called for that inode. This points to memory scribble, or synchronisation problme. i_state of I_NEW inodes is not protected by inode_lock because other processes are not supposed to touch them until I_LOCK (and I_NEW) is cleared. Adding WARN_ON(inode->i_state & I_NEW) to sites where we modify i_state revealed that generic_sync_sb_inodes is picking up new inodes from the inode lists and passing them to __writeback_single_inode without waiting for I_NEW. Subsequently modifying i_state causes corruption. In my case it would look like this: CPU0 CPU1 unlock_new_inode() __sync_single_inode() reg <- inode->i_state reg -> reg & ~(I_LOCK|I_NEW) reg <- inode->i_state reg -> inode->i_state reg -> reg | I_SYNC reg -> inode->i_state Non-atomic RMW on CPU1 overwrites CPU0 store and sets I_LOCK|I_NEW again. Fix for this is rather than wait for I_NEW inodes, just skip over them: inodes concurrently being created are not subject to data integrity operations, and should not significantly contribute to dirty memory either. After this change, I'm unable to reproduce any of the added warnings or hangs after ~1hour of running. Previously, the new warnings would start immediately and hang would happen in under 5 minutes. I'm also testing on ext3 now, and so far no problems there either. I don't know whether this fixes the problem reported above, but it fixes a real problem for me. Cc: "Jorge Boncompte [DTI2]" Reported-by: Adrian Hunter Cc: Jan Kara Cc: Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fs: sys_sync fix

2009-01-06T23:59:09+00:00

s_syncing livelock avoidance was breaking data integrity guarantee of sys_sync, by allowing sys_sync to skip writing or waiting for superblocks if there is a concurrent sys_sync happening. This livelock avoidance is much less important now that we don't have the get_super_to_sync() call after every sb that we sync. This was replaced by __put_super_and_need_restart. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fs: sync_sb_inodes fix

2009-01-06T23:59:09+00:00

Fix data integrity semantics required by sys_sync, by iterating over all inodes and waiting for any writeback pages after the initial writeout. Comments explain the exact problem. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fs: remove WB_SYNC_HOLD

2009-01-06T23:59:09+00:00

Remove WB_SYNC_HOLD. The primary motiviation is the design of my anti-starvation code for fsync. It requires taking an inode lock over the sync operation, so we could run into lock ordering problems with multiple inodes. It is possible to take a single global lock to solve the ordering problem, but then that would prevent a future nice implementation of "sync multiple inodes" based on lock order via inode address. Seems like a backward step to remove this, but actually it is busted anyway: we can't use the inode lists for data integrity wait: an inode can be taken off the dirty lists but still be under writeback. In order to satisfy data integrity semantics, we should wait for it to finish writeback, but if we only search the dirty lists, we'll miss it. It would be possible to have a "writeback" list, for sys_sync, I suppose. But why complicate things by prematurely optimise? For unmounting, we could avoid the "livelock avoidance" code, which would be easier, but again premature IMO. Fixing the existing data integrity problem will come next. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Remove Andrew Morton's old email accounts

2008-10-16T18:21:32+00:00

People can use the real name an an index into MAINTAINERS to find the current email address. Signed-off-by: Francois Cami Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

VFS: export sync_sb_inodes

2008-07-14T16:10:52+00:00

This patch exports the 'sync_sb_inodes()' which is needed for UBIFS because it has to force write-back from time to time. Namely, the UBIFS budgeting subsystem forces write-back when its pessimistic callculations show that there is no free space on the media. Signed-off-by: Artem Bityutskiy

VFS: move inode_lock into sync_sb_inodes

2008-07-14T16:10:52+00:00

This patch makes 'sync_sb_inodes()' lock 'inode_lock', rather than expect that the caller will do this. This change was previously done by Hans Reiser and sat in the -mm tree. Signed-off-by: Artem Bityutskiy

fs/fs-writeback.c: make 2 functions static

2008-04-29T15:06:00+00:00

Make the following needlessly global functions static: - writeback_acquire() - writeback_release() Signed-off-by: Adrian Bunk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds