get_user_pages_unlocked(): pass true to __get_user_pages_locked() notify_drop
Equivalent transformation - the only place in __get_user_pages_locked() where we look at notify_drop argument is if (notify_drop && lock_dropped && *locked) { up_read(&mm->mmap_sem); *locked = 0; } in the very end. Changing notify_drop from false to true won't change behaviour unless *locked is non-zero. The caller is ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL, &locked, false, gup_flags | FOLL_TOUCH); if (locked) up_read(&mm->mmap_sem); so in that case the original kernel would have done up_read() right after return from __get_user_pages_locked(), while the modified one would've done it right before the return. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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2
mm/gup.c
2
mm/gup.c
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@ -988,7 +988,7 @@ long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
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down_read(&mm->mmap_sem);
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ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
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&locked, false, gup_flags | FOLL_TOUCH);
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&locked, true, gup_flags | FOLL_TOUCH);
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if (locked)
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up_read(&mm->mmap_sem);
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return ret;
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