drm/amdgpu: add a bool to specify if needing vm flush V2

[karo-tx-linux.git] / kernel / futex.c

diff --git a/kernel/futex.c b/kernel/futex.c
index ee25f5ba4aca13f8a05a9e6c3a4c5a2aff768131..33664f70e2d25e880efdbc8695fcc12989871150 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -469,7 +469,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
 {
        unsigned long address = (unsigned long)uaddr;
        struct mm_struct *mm = current->mm;
-       struct page *page;
+       struct page *page, *tail;
        struct address_space *mapping;
        int err, ro = 0;
 
@@ -530,7 +530,15 @@ again:
         * considered here and page lock forces unnecessarily serialization
         * From this point on, mapping will be re-verified if necessary and
         * page lock will be acquired only if it is unavoidable
-        */
+        *
+        * Mapping checks require the head page for any compound page so the
+        * head page and mapping is looked up now. For anonymous pages, it
+        * does not matter if the page splits in the future as the key is
+        * based on the address. For filesystem-backed pages, the tail is
+        * required as the index of the page determines the key. For
+        * base pages, there is no tail page and tail == page.
+        */
+       tail = page;
        page = compound_head(page);
        mapping = READ_ONCE(page->mapping);
 
@@ -654,7 +662,7 @@ again:
 
                key->both.offset |= FUT_OFF_INODE; /* inode-based key */
                key->shared.inode = inode;
-               key->shared.pgoff = basepage_index(page);
+               key->shared.pgoff = basepage_index(tail);
                rcu_read_unlock();
        }