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Linus Torvalds cd1adf1b63 Revert "mm/gup: remove try_get_page(), call try_get_compound_head() directly" 
This reverts commit 9857a17f20.

That commit was completely broken, and I should have caught on to it
earlier.  But happily, the kernel test robot noticed the breakage fairly
quickly.

The breakage is because "try_get_page()" is about avoiding the page
reference count overflow case, but is otherwise the exact same as a
plain "get_page()".

In contrast, "try_get_compound_head()" is an entirely different beast,
and uses __page_cache_add_speculative() because it's not just about the
page reference count, but also about possibly racing with the underlying
page going away.

So all the commentary about how

 "try_get_page() has fallen a little behind in terms of maintenance,
  try_get_compound_head() handles speculative page references more
  thoroughly"

was just completely wrong: yes, try_get_compound_head() handles
speculative page references, but the point is that try_get_page() does
not, and must not.

So there's no lack of maintainance - there are fundamentally different
semantics.

A speculative page reference would be entirely wrong in "get_page()",
and it's entirely wrong in "try_get_page()".  It's not about
speculation, it's purely about "uhhuh, you can't get this page because
you've tried to increment the reference count too much already".

The reason the kernel test robot noticed this bug was that it hit the
VM_BUG_ON() in __page_cache_add_speculative(), which is all about
verifying that the context of any speculative page access is correct.
But since that isn't what try_get_page() is all about, the VM_BUG_ON()
tests things that are not correct to test for try_get_page().

Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-07 11:03:45 -07:00
..
9p overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
adfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
affs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
afs fs: remove mandatory file locking support 2021-08-23 06:15:36 -04:00
autofs autofs: should_expire() argument is guaranteed to be positive 2021-03-24 14:14:27 -04:00
befs isystem: ship and use stdarg.h 2021-08-19 09:02:55 +09:00
bfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
btrfs overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
cachefiles cachefiles: Change %p in format strings to something else 2021-08-27 13:34:02 +01:00
ceph overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
cifs 11 cifs/smb3 client fixes, including some restructuring to allow disabling less secure algorithms, and 2 for stable 2021-08-31 09:22:37 -07:00
cifs_common cifs: cifs_md4 convert to SPDX identifier 2021-08-25 15:51:52 -05:00
coda coda: fix reference counting in coda_file_mmap error path 2021-04-23 14:42:39 -07:00
configfs configfs: fix a race in configfs_lookup() 2021-08-25 07:58:49 +02:00
cramfs
crypto fscrypt: align Base64 encoding with RFC 4648 base64url 2021-07-25 20:47:05 -07:00
debugfs debugfs: Return error during {full/open}_proxy_open() on rmmod 2021-08-05 14:42:40 +02:00
devpts
dlm fs: dlm: avoid comms shutdown delay in release_lockspace 2021-09-01 11:29:14 -05:00
ecryptfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
efivarfs efivars: convert to fileattr 2021-04-12 15:04:29 +02:00
efs
erofs overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
exfat Description for this pull request: 2021-07-06 11:06:04 -07:00
exportfs
ext2 overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
ext4 In addition to some ext4 bug fixes and cleanups, this cycle we add the 2021-09-02 09:37:09 -07:00
f2fs f2fs-for-5.15-rc1 2021-09-04 10:48:47 -07:00
fat linux-kselftest-kunit-5.15-rc1 2021-09-02 12:32:12 -07:00
freevxfs
fscache fscache: Use refcount_t for the cookie refcount instead of atomic_t 2021-08-27 13:34:03 +01:00
fuse overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
gfs2 overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
hfs hfs: add lock nesting notation to hfs_find_init 2021-07-15 10:13:49 -07:00
hfsplus hfsplus: report create_date to kstat.btime 2021-07-01 11:06:06 -07:00
hostfs Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-05-02 09:14:01 -07:00
hpfs hpfs: use iomap_fiemap to implement ->fiemap 2021-07-27 11:00:36 +02:00
hugetlbfs hugetlbfs: fix mount mode command line processing 2021-07-23 17:43:28 -07:00
iomap iomap: standardize tracepoint formatting and storage 2021-08-26 09:18:53 -07:00
isofs isofs: joliet: Fix iocharset=utf8 mount option 2021-08-12 16:07:14 +02:00
jbd2 ext4: Support for checksumming from journal triggers 2021-08-30 23:36:50 -04:00
jffs2 vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
jfs vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
kernfs kernfs: dont call d_splice_alias() under kernfs node lock 2021-07-27 09:29:15 +02:00
ksmbd ksmbd: fix __write_overflow warning in ndr_read_string 2021-08-27 14:03:49 -05:00
lockd NFS Client Updates for Linux 5.15 2021-09-04 10:25:26 -07:00
minix mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
netfs netfs: fix test for whether we can skip read when writing beyond EOF 2021-06-21 21:24:07 +01:00
nfs NFS Client Updates for Linux 5.15 2021-09-04 10:25:26 -07:00
nfs_common nfs_common: fix doc warning 2021-07-06 20:14:41 -04:00
nfsd SCSI misc on 20210902 2021-09-02 15:09:46 -07:00
nilfs2 block: remove the bd_bdi in struct block_device 2021-08-09 11:53:26 -06:00
nls
notify \n 2021-08-30 10:04:31 -07:00
ntfs Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-07-03 11:30:04 -07:00
ntfs3 Merge git://github.com/Paragon-Software-Group/linux-ntfs3 2021-09-04 11:15:50 -07:00
ocfs2 Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
omfs mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
openpromfs openpromfs: don't do unlock_new_inode() until the new inode is set up 2021-03-12 22:15:22 -05:00
orangefs vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
overlayfs ovl: enable RCU'd ->get_acl() 2021-08-18 22:08:24 +02:00
proc mm: remove VM_DENYWRITE 2021-09-03 18:42:01 +02:00
pstore for-5.14/drivers-2021-06-29 2021-06-30 12:21:16 -07:00
qnx4
qnx6
quota quota: remove unnecessary oom message 2021-06-22 10:40:52 +02:00
ramfs fs: move ramfs_aops to libfs 2021-06-29 10:53:48 -07:00
reiserfs Kbuild updates for v5.15 2021-09-03 15:33:47 -07:00
romfs
squashfs squashfs: use bvec_virt 2021-08-16 10:50:32 -06:00
sysfs sysfs: Allow deferred execution of iomem_get_mapping() 2021-08-06 13:05:28 +02:00
sysv mm: require ->set_page_dirty to be explicitly wired up 2021-06-29 10:53:48 -07:00
tracefs tracing: Fix various typos in comments 2021-03-23 14:08:18 -04:00
ubifs ubifs: report correct st_size for encrypted symlinks 2021-07-25 20:01:07 -07:00
udf udf_get_extendedattr() had no boundary checks. 2021-08-23 13:35:19 +02:00
ufs isystem: ship and use stdarg.h 2021-08-19 09:02:55 +09:00
unicode .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
vboxsf vboxsf: Add support for the atomic_open directory-inode op 2021-06-23 14:36:52 +02:00
verity fsverity: relax build time dependency on CRYPTO_SHA256 2021-04-22 17:31:32 +10:00
xfs overlayfs update for 5.15 2021-09-02 09:21:27 -07:00
zonefs \n 2021-08-30 10:24:50 -07:00
aio.c eventfd: Make signal recursion protection a task bit 2021-08-28 01:33:02 +02:00
anon_inodes.c
attr.c
bad_inode.c vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
binfmt_aout.c binfmt: a.out: Fix bogus semicolon 2021-09-05 10:15:05 -07:00
binfmt_elf_fdpic.c binfmt: remove in-tree usage of MAP_DENYWRITE 2021-09-03 18:42:01 +02:00
binfmt_elf.c binfmt: remove in-tree usage of MAP_DENYWRITE 2021-09-03 18:42:01 +02:00
binfmt_flat.c binfmt: remove in-tree usage of MAP_EXECUTABLE 2021-06-29 10:53:50 -07:00
binfmt_misc.c binfmt_misc: fix possible deadlock in bm_register_write 2021-03-13 11:27:30 -08:00
binfmt_script.c
block_dev.c io_uring-bio-cache.5-2021-08-30 2021-08-30 19:30:30 -07:00
buffer.c Merge branch 'exit-cleanups-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-09-01 14:52:05 -07:00
char_dev.c
compat_binfmt_elf.c
coredump.c Merge branch 'work.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-07-03 11:41:14 -07:00
d_path.c d_path: make 'prepend()' fill up the buffer exactly on overflow 2021-09-02 10:07:29 -07:00
dax.c New code for 5.15: 2021-08-31 11:13:35 -07:00
dcache.c useful constants: struct qstr for ".." 2021-04-15 22:36:45 -04:00
direct-io.c fs: direct-io: fix missing sdio->boundary 2021-04-09 14:54:23 -07:00
drop_caches.c fs: drop_caches: fix skipping over shadow cache inodes 2021-09-03 09:58:10 -07:00
eventfd.c eventfd: Make signal recursion protection a task bit 2021-08-28 01:33:02 +02:00
eventpoll.c fs/epoll: restore waking from ep_done_scan() 2021-05-06 19:24:13 -07:00
exec.c Merge tag 'denywrite-for-5.15' of git://github.com/davidhildenbrand/linux 2021-09-04 11:35:47 -07:00
fcntl.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
fhandle.c switch file_open_root() to struct path 2021-04-07 13:56:43 -04:00
file_table.c
file.c fs.close_range.v5.15 2021-08-31 12:00:07 -07:00
filesystems.c
fs_context.c memcg: charge fs_context and legacy_fs_context 2021-09-03 09:58:12 -07:00
fs_parser.c vfs: fs_parser: clean up kernel-doc warnings 2021-04-30 11:20:35 -07:00
fs_pin.c
fs_struct.c
fs_types.c
fs-writeback.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
fsopen.c
init.c
inode.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
internal.h New code for 5.15: 2021-08-31 11:13:35 -07:00
io_uring.c for-5.15/io_uring-2021-09-04 2021-09-06 09:26:07 -07:00
io-wq.c io-wq: make worker creation resilient against signals 2021-09-02 11:12:19 -06:00
io-wq.h io-wq: provide a way to limit max number of workers 2021-08-29 07:55:55 -06:00
ioctl.c New code for 5.15: 2021-08-31 11:06:32 -07:00
Kconfig Merge git://github.com/Paragon-Software-Group/linux-ntfs3 2021-09-04 11:15:50 -07:00
Kconfig.binfmt binfmt: remove support for em86 (alpha only) 2021-07-25 22:33:03 -07:00
kernel_read_file.c switch file_open_root() to struct path 2021-04-07 13:56:43 -04:00
libfs.c fs: remove noop_set_page_dirty() 2021-06-29 10:53:48 -07:00
locks.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
Makefile Merge git://github.com/Paragon-Software-Group/linux-ntfs3 2021-09-04 11:15:50 -07:00
mbcache.c
mount.h
mpage.c block: rename BIO_MAX_PAGES to BIO_MAX_VECS 2021-03-11 07:47:48 -07:00
namei.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
namespace.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
no-block.c
nsfs.c
open.c fs: remove mandatory file locking support 2021-08-23 06:15:36 -04:00
pipe.c Revert "mm/gup: remove try_get_page(), call try_get_compound_head() directly" 2021-09-07 11:03:45 -07:00
pnode.c
pnode.h mount: fix mounting of detached mounts onto targets that reside on shared mounts 2021-03-08 15:18:43 +01:00
posix_acl.c ovl: enable RCU'd ->get_acl() 2021-08-18 22:08:24 +02:00
proc_namespace.c
read_write.c fs: clean up after mandatory file locking support removal 2021-08-24 07:52:45 -04:00
readdir.c readdir: make sure to verify directory entry for legacy interfaces too 2021-04-17 11:39:49 -07:00
remap_range.c fs: remove mandatory file locking support 2021-08-23 06:15:36 -04:00
select.c memcg: enable accounting for pollfd and select bits arrays 2021-09-03 09:58:12 -07:00
seq_file.c seq_file: disallow extremely large seq buffer allocations 2021-07-19 17:18:48 -07:00
signalfd.c signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency 2021-07-23 13:16:43 -05:00
splice.c for-5.12/block-2021-02-17 2021-02-21 11:02:48 -08:00
stack.c
stat.c fs: add generic helper for filling statx attribute flags 2021-08-17 11:47:43 +02:00
statfs.c
super.c block: remove the bd_bdi in struct block_device 2021-08-09 11:53:26 -06:00
sync.c
timerfd.c timerfd: Provide timerfd_resume() 2021-08-10 17:57:22 +02:00
userfaultfd.c userfaultfd: prevent concurrent API initialization 2021-09-03 09:58:16 -07:00
utimes.c
xattr.c xattr: fix kernel-doc for mnt_userns and vfs xattr helpers 2021-03-23 11:20:26 +01:00