Commit 47e20933814feeb75543eb514437989cea53ec52
Committed by
Greg Kroah-Hartman
Greg Kroah-Hartman
1 parent
1402105542
mm/filemap.c: don't bother dropping mmap_sem for zero size readahead
commit 5c72feee3e45b40a3c96c7145ec422899d0e8964 upstream. When handling a page fault, we drop mmap_sem to start async readahead so that we don't block on IO submission with mmap_sem held. However there's no point to drop mmap_sem in case readahead is disabled. Handle that case to avoid pointless dropping of mmap_sem and retrying the fault. This was actually reported to block mlockall(MCL_CURRENT) indefinitely. Fixes: 6b4c9f446981 ("filemap: drop the mmap_sem for all blocking operations") Reported-by: Minchan Kim <minchan@kernel.org> Reported-by: Robert Stupp <snazy@gmx.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Link: http://lkml.kernel.org/r/20200212101356.30759-1-jack@suse.cz Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: SeongJae Park <sjpark@amazon.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Showing 1 changed file with 1 additions and 1 deletions Side-by-side Diff
mm/filemap.c
| ... | ... | @@ -2438,7 +2438,7 @@ |
| 2438 | 2438 | pgoff_t offset = vmf->pgoff; |
| 2439 | 2439 | |
| 2440 | 2440 | /* If we don't want any read-ahead, don't bother */ |
| 2441 | - if (vmf->vma->vm_flags & VM_RAND_READ) | |
| 2441 | + if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) | |
| 2442 | 2442 | return fpin; |
| 2443 | 2443 | if (ra->mmap_miss > 0) |
| 2444 | 2444 | ra->mmap_miss--; |