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authorJohn Hubbard <[email protected]>2022-02-01 19:23:17 -0800
committerLinus Torvalds <[email protected]>2022-02-03 06:51:42 -0800
commitc36c04c2e132fc39f6b658bf607aed4425427fd7 (patch)
tree749938c541b52a6b432c1fd06493d42216320adb /tools/perf/scripts/python/syscall-counts.py
parentd394bb77dd0bd20b125459da25fdac00a853be28 (diff)
Revert "mm/gup: small refactoring: simplify try_grab_page()"
This reverts commit 54d516b1d62ff8f17cee2da06e5e4706a0d00b8a That commit did a refactoring that effectively combined fast and slow gup paths (again). And that was again incorrect, for two reasons: a) Fast gup and slow gup get reference counts on pages in different ways and with different goals: see Linus' writeup in commit cd1adf1b63a1 ("Revert "mm/gup: remove try_get_page(), call try_get_compound_head() directly""), and b) try_grab_compound_head() also has a specific check for "FOLL_LONGTERM && !is_pinned(page)", that assumes that the caller can fall back to slow gup. This resulted in new failures, as recently report by Will McVicker [1]. But (a) has problems too, even though they may not have been reported yet. So just revert this. Link: https://lore.kernel.org/r/[email protected] [1] Fixes: 54d516b1d62f ("mm/gup: small refactoring: simplify try_grab_page()") Reported-and-tested-by: Will McVicker <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: Christian Borntraeger <[email protected]> Cc: Heiko Carstens <[email protected]> Cc: Vasily Gorbik <[email protected]> Cc: [email protected] # 5.15 Signed-off-by: John Hubbard <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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