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authorJan Kara <jack@suse.cz>2012-05-03 14:48:03 +0200
committerFengguang Wu <fengguang.wu@intel.com>2012-05-06 13:43:41 +0800
commit169ebd90131b2ffca74bb2dbe7eeacd39fb83714 (patch)
tree513136e110970da388680947c225ef8ca05a6dd7 /fs/gfs2
parentdbd5768f87ff6fb0a4fe09c4d7b6c4a24de99430 (diff)
downloadlinux-169ebd90131b2ffca74bb2dbe7eeacd39fb83714.tar.bz2
writeback: Avoid iput() from flusher thread
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 <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
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