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David Chinner authored
If we allow incore extent tree allocations to recurse into the filesystem under memory pressure, new delayed allocations through xfs_iomap_write_delay() can deadlock on themselves if memory reclaim tries to write back dirty pages from that inode. It will deadlock in xfs_iomap_write_allocate() trying to take the ilock we already hold. This can also show up as complex ABBA deadlocks when multiple threads are triggering memory reclaim when trying to allocate extents. The main cause of this is the fact that delayed allocation is not done in a transaction, so KM_NOFS is not automatically added to the allocations to prevent this recursion. Mark all allocations done for the incore inode extent tree as KM_NOFS to ensure they never recurse back into the filesystem. Version 2: o KM_NOFS implies KM_SLEEP, so just use KM_NOFS SGI-PV: 981498 SGI-Modid: xfs-linux-melb:xfs-kern:31726a Signed-off-by: David Chinner <david@fromorbit.com> Signed-off-by: Niv Sardi <xaiki@sgi.com> Signed-off-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
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