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| author | Huang Ying <ying.huang@intel.com> | 2017-05-03 14:54:33 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-05-03 15:52:10 -0700 |
| commit | 9c1cc2e4f25c14dc1a2d98e98808aefef24abaf4 (patch) | |
| tree | 90d7fbefa4ba009604633ce8d06cd8e3c64d3fac /mm | |
| parent | 83612a948d3bd2e71b110d7e8735661621bd23d9 (diff) | |
| download | op-kernel-dev-9c1cc2e4f25c14dc1a2d98e98808aefef24abaf4.zip op-kernel-dev-9c1cc2e4f25c14dc1a2d98e98808aefef24abaf4.tar.gz | |
mm, swap: fix comment in __read_swap_cache_async
Commit cbab0e4eec29 ("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 815c2c543d3a ("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 cbab0e4eec29 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.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/swap_state.c | 12 |
1 files changed, 1 insertions, 11 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c index 473b71e..7bfb9bd 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -360,17 +360,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, /* * We might race against get_swap_page() and stumble * across a SWAP_HAS_CACHE swap_map entry whose page - * has not been brought into the swapcache yet, while - * the other end is scheduled away waiting on discard - * I/O completion at scan_swap_map(). - * - * In order to avoid turning this transitory state - * into a permanent loop around this -EEXIST case - * if !CONFIG_PREEMPT and the I/O completion happens - * to be waiting on the CPU waitqueue where we are now - * busy looping, we just conditionally invoke the - * scheduler here, if there are some more important - * tasks to run. + * has not been brought into the swapcache yet. */ cond_resched(); continue; |
