# git rev-parse -q --verify c36c04c2e132fc39f6b658bf607aed4425427fd7^{commit}
c36c04c2e132fc39f6b658bf607aed4425427fd7
already have revision, skipping fetch
# git checkout -q -f -B kisskb c36c04c2e132fc39f6b658bf607aed4425427fd7
# git clean -qxdf
# < git log -1
# commit c36c04c2e132fc39f6b658bf607aed4425427fd7
# Author: John Hubbard <jhubbard@nvidia.com>
# Date:   Tue Feb 1 19:23:17 2022 -0800
# 
#     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/20220131203504.3458775-1-willmcvicker@google.com [1]
#     Fixes: 54d516b1d62f ("mm/gup: small refactoring: simplify try_grab_page()")
#     Reported-and-tested-by: Will McVicker <willmcvicker@google.com>
#     Cc: Christoph Hellwig <hch@lst.de>
#     Cc: Minchan Kim <minchan@google.com>
#     Cc: Matthew Wilcox <willy@infradead.org>
#     Cc: Christian Borntraeger <borntraeger@de.ibm.com>
#     Cc: Heiko Carstens <hca@linux.ibm.com>
#     Cc: Vasily Gorbik <gor@linux.ibm.com>
#     Cc: stable@vger.kernel.org # 5.15
#     Signed-off-by: John Hubbard <jhubbard@nvidia.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 c36c04c2e132fc39f6b658bf607aed4425427fd7
# < make -s -j 32 ARCH=powerpc O=/kisskb/build/linus_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  ppc64_defconfig
# < make -s -j 32 ARCH=powerpc O=/kisskb/build/linus_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 32 ARCH=powerpc O=/kisskb/build/linus_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 32 ARCH=powerpc O=/kisskb/build/linus_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/linus_ppc64_defconfig_powerpc-gcc5
# Build took: 0:02:17.232996