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27 March 2024, 02:37:15 UTC
Revision 7e09e738afd21ef99f047425fc0b0c9be8b03254 authored by Hugh Dickins on 21 March 2014, 04:52:17 UTC, committed by Linus Torvalds on 21 March 2014, 05:09:09 UTC 
mm: fix swapops.h:131 bug if remap_file_pages raced migration
 
Add remove_linear_migration_ptes_from_nonlinear(), to fix an interesting
little include/linux/swapops.h:131 BUG_ON(!PageLocked) found by trinity:
indicating that remove_migration_ptes() failed to find one of the
migration entries that was temporarily inserted.

The problem comes from remap_file_pages()'s switch from vma_interval_tree
(good for inserting the migration entry) to i_mmap_nonlinear list (no good
for locating it again); but can only be a problem if the remap_file_pages()
range does not cover the whole of the vma (zap_pte() clears the range).

remove_migration_ptes() needs a file_nonlinear method to go down the
i_mmap_nonlinear list, applying linear location to look for migration
entries in those vmas too, just in case there was this race.

The file_nonlinear method does need rmap_walk_control.arg to do this;
but it never needed vma passed in - vma comes from its own iteration.

Reported-and-tested-by: Dave Jones <davej@redhat.com>
Reported-and-tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 3fb725c
History
Tip revision: 7e09e738afd21ef99f047425fc0b0c9be8b03254 authored by Hugh Dickins on 21 March 2014, 04:52:17 UTC
mm: fix swapops.h:131 bug if remap_file_pages raced migration
Tip revision: 7e09e73
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