linux/fs/fs-writeback.c, branch v3.5

writeback: Fix lock imbalance in writeback_sb_inodes()

2012-06-08T23:32:15Z

Fix bug introduced by 169ebd90. We have to have wb_list_lock locked when restarting writeback loop after having waited for inode writeback. Bug description by Ted Tso: I can reproduce this fairly easily by using ext4 w/o a journal, running under KVM with 1024megs memory, with fsstress (xfstests #13): [ 45.153294] ===================================== [ 45.154784] [ BUG: bad unlock balance detected! ] [ 45.155591] 3.5.0-rc1-00002-gb22b1f1 #124 Not tainted [ 45.155591] ------------------------------------- [ 45.155591] flush-254:16/2499 is trying to release lock (&(&wb->list_lock)->rlock) at: [ 45.155591] [] writeback_sb_inodes+0x160/0x327 [ 45.155591] but there are no more locks to release! Reported-by: Theodore Ts'o Tested-by: Theodore Ts'o Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

writeback: Avoid iput() from flusher thread

2012-05-06T05:43:41Z

Doing iput() from flusher thread (writeback_sb_inodes()) can create problems because iput() can do a lot of work - for example truncate the inode if it's the last iput on unlinked file. Some filesystems depend on flusher thread progressing (e.g. because they need to flush delay allocated blocks to reduce allocation uncertainty) and so flusher thread doing truncate creates interesting dependencies and possibilities for deadlocks. We get rid of iput() in flusher thread by using the fact that I_SYNC inode flag effectively pins the inode in memory. So if we take care to either hold i_lock or have I_SYNC set, we can get away without taking inode reference in writeback_sb_inodes(). As a side effect of these changes, we also fix possible use-after-free in wb_writeback() because inode_wait_for_writeback() call could try to reacquire i_lock on the inode that was already free. Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

writeback: Refactor writeback_single_inode()

2012-05-06T05:43:40Z

The code in writeback_single_inode() is relatively complex. The list requeing logic makes sense only for flusher thread but not really for sync_inode() or write_inode_now() callers. Also when we want to get rid of inode references held by flusher thread, we will need a special I_SYNC handling there. So separate part of writeback_single_inode() which does the real writeback work into __writeback_single_inode() and make writeback_single_inode() do only stuff necessary for callers writing only one inode, moving the special list handling into writeback_sb_inodes(). As a sideeffect this fixes a possible race where we could skip some inode during sync(2) because other writer refiled it from b_io to b_dirty list. Also I_SYNC handling is moved into the callers of __writeback_single_inode() to make locking easier. Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

writeback: Remove wb->list_lock from writeback_single_inode()

2012-05-06T05:43:39Z

writeback_single_inode() doesn't need wb->list_lock for anything on entry now. So remove the requirement. This makes locking of writeback_single_inode() temporarily awkward (entering with i_lock, returning with i_lock and wb->list_lock) but it will be sanitized in the next patch. Also inode_wait_for_writeback() doesn't need wb->list_lock for anything. It was just taking it to make usage convenient for callers but with writeback_single_inode() changing it's not very convenient anymore. So remove the lock from that function. Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

writeback: Separate inode requeueing after writeback

2012-05-06T05:43:39Z

Move inode requeueing after inode has been written out into a separate function. Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

writeback: Move I_DIRTY_PAGES handling

2012-05-06T05:43:39Z

Instead of clearing I_DIRTY_PAGES and resetting it when we didn't succeed in writing them all, just clear the bit only when we succeeded writing all the pages. We also move the clearing of the bit close to other i_state handling to separate it from writeback list handling. This is desirable because list handling will differ for flusher thread and other writeback_single_inode() callers in future. No filesystem plays any tricks with I_DIRTY_PAGES (like checking it in ->writepages or ->write_inode implementation) so this movement is safe. Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

writeback: Move requeueing when I_SYNC set to writeback_sb_inodes()

2012-05-06T05:43:38Z

When writeback_single_inode() is called on inode which has I_SYNC already set while doing WB_SYNC_NONE, inode is moved to b_more_io list. However this makes sense only if the caller is flusher thread. For other callers of writeback_single_inode() it doesn't really make sense and may be even wrong - flusher thread may be doing WB_SYNC_ALL writeback in parallel. So we move requeueing from writeback_single_inode() to writeback_sb_inodes(). Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

writeback: Move clearing of I_SYNC into inode_sync_complete()

2012-05-06T05:43:38Z

Move clearing of I_SYNC into inode_sync_complete(). It is more logical to have clearing of I_SYNC bit and waking of waiters in one place. Also later we will have two places needing to clear I_SYNC and wake up waiters so this allows them to use the common helper. Moving of I_SYNC clearing to a later stage of writeback_single_inode() is safe since we hold i_lock all the time. Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Fengguang Wu

Merge tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux

2012-03-28T17:07:27Z

Pull trivial writeback fixes from Wu Fengguang: "They've been tested in linux-next for 20 days actually." * tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: writeback: Remove outdated comment fs: Remove bogus wait in write_inode_now()

Merge tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux

2012-03-24T17:24:31Z

Pull cleanup of fs/ and lib/ users of module.h from Paul Gortmaker: "Fix up files in fs/ and lib/ dirs to only use module.h if they really need it. These are trivial in scope vs the work done previously. We now have things where any few remaining cleanups can be farmed out to arch or subsystem maintainers, and I have done so when possible. What is remaining here represents the bits that don't clearly lie within a single arch/subsystem boundary, like the fs dir and the lib dir. Some duplicate includes arising from overlapping fixes from independent subsystem maintainer submissions are also quashed." Fix up trivial conflicts due to clashes with other include file cleanups (including some due to the previous bug.h cleanup pull). * tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: lib: reduce the use of module.h wherever possible fs: reduce the use of module.h wherever possible includecheck: delete any duplicate instances of module.h