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Brian Behlendorf
74328ee18f
There exists a lock inversions involving the zfs range lock and the individual page writeback bits which can result in a deadlock. To prevent this we must always manipulate the writeback bit while holding the range lock. The exact deadlock is as follows: ------ Process A ------ ------ Process B ------ zpl_writepages zpl_fallocate write_cache_pages zpl_fallocate_common zpl_putpage zfs_space zfs_putpage (set bit) zfs_freesp zfs_range_lock (wait on lock) zfs_free_range (take lock) [has not yet initiated I/O, truncate_inode_pages_range the bit will not be cleared] wait_on_page_writeback (wait on bit) Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Richard Yao <richard.yao@clusterhq.com> Issue #2976