mm, swap: fix comment in __read_swap_cache_async
Commit cbab0e4e ("swap: avoid read_swap_cache_async() race to deadlock while waiting on discard I/O completion") fixed a deadlock in read_swap_cache_async(). Because at that time, in swap allocation path, a swap entry may be set as SWAP_HAS_CACHE, then wait for discarding to complete before the page for the swap entry is added to the swap cache. But in commit 815c2c54 ("swap: make swap discard async"), the discarding for swap become asynchronous, waiting for discarding to complete will be done before the swap entry is set as SWAP_HAS_CACHE. So the comments in code is incorrect now. This patch fixes the comments. The cond_resched() added in the commit cbab0e4e is not necessary now too. But if we added some sleep in swap allocation path in the future, there may be some hard to debug/reproduce deadlock bug. So it is kept. Link: http://lkml.kernel.org/r/20170317064635.12792-1-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com> Acked-by: NRafael Aquini <aquini@redhat.com> Cc: Shaohua Li <shli@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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