This cycle we ported all filesystems to the new posix acl api. While
looking at further simplifications in this area to remove the last
remnants of the generic dummy posix acl handlers we realized that we
regressed fuse daemons that don't set FUSE_POSIX_ACL but still make use
of posix acls.

With the change to a dedicated posix acl api interacting with posix acls
doesn't go through the old xattr codepaths anymore and instead only
relies the get acl and set acl inode operations.

Before this change fuse daemons that don't set FUSE_POSIX_ACL were able
to get and set posix acl albeit with two caveats. First, that posix acls
aren't cached. And second, that they aren't used for permission checking
in the vfs.

We regressed that use-case as we currently refuse to retrieve any posix
acls if they aren't enabled via FUSE_POSIX_ACL. So older fuse daemons
would see a change in behavior.

We can restore the old behavior in multiple ways. We could change the
new posix acl api and look for a dedicated xattr handler and if we find
one prefer that over the dedicated posix acl api. That would break the
consistency of the new posix acl api so we would very much prefer not to
do that.

We could introduce a new ACL_*_CACHE sentinel that would instruct the
vfs permission checking codepath to not call into the filesystem and
ignore acls.

But a more straightforward fix for v6.2 is to do the same thing that
Overlayfs does and give fuse a separate get acl method for permission
checking. Overlayfs uses this to express different needs for vfs
permission lookup and acl based retrieval via the regular system call
path as well. Let fuse do the same for now. This way fuse can continue
to refuse to retrieve posix acls for daemons that don't set
FUSE_POSXI_ACL for permission checking while allowing a fuse server to
retrieve it via the usual system calls.

In the future, we could extend the get acl inode operation to not just
pass a simple boolean to indicate rcu lookup but instead make it a flag
argument. Then in addition to passing the information that this is an
rcu lookup to the filesystem we could also introduce a flag that tells
the filesystem that this is a request from the vfs to use these acls for
permission checking. Then fuse could refuse the get acl request for
permission checking when the daemon doesn't have FUSE_POSIX_ACL set in
the same get acl method. This would also help Overlayfs and allow us to
remove the second method for it as well.

But since that change is more invasive as we need to update the get acl
inode operation for multiple filesystems we should not do this as a fix
for v6.2. Instead we will do this for the v6.3 merge window.

Fwiw, since posix acls are now always correctly translated in the new
posix acl api we could also allow them to be used for daemons without
FUSE_POSIX_ACL that are not mounted on the host. But this is behavioral
change and again if dones should be done for v6.3. For now, let's just
restore the original behavior.

A nice side-effect of this change is that for fuse daemons with and
without FUSE_POSIX_ACL the same code is used for posix acls in a
backwards compatible way. This also means we can remove the legacy xattr
handlers completely. We've also added comments to explain the expected
behavior for daemons without FUSE_POSIX_ACL into the code.

Fixes: 318e66856dde ("xattr: use posix acl api")
Signed-off-by: Seth Forshee (Digital Ocean) <sforshee@kernel.org>
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

Pull MM updates from Andrew Morton:

 - More userfaultfs work from Peter Xu

 - Several convert-to-folios series from Sidhartha Kumar and Huang Ying

 - Some filemap cleanups from Vishal Moola

 - David Hildenbrand added the ability to selftest anon memory COW
   handling

 - Some cpuset simplifications from Liu Shixin

 - Addition of vmalloc tracing support by Uladzislau Rezki

 - Some pagecache folioifications and simplifications from Matthew
   Wilcox

 - A pagemap cleanup from Kefeng Wang: we have VM_ACCESS_FLAGS, so use
   it

 - Miguel Ojeda contributed some cleanups for our use of the
   __no_sanitize_thread__ gcc keyword.

   This series should have been in the non-MM tree, my bad

 - Naoya Horiguchi improved the interaction between memory poisoning and
   memory section removal for huge pages

 - DAMON cleanups and tuneups from SeongJae Park

 - Tony Luck fixed the handling of COW faults against poisoned pages

 - Peter Xu utilized the PTE marker code for handling swapin errors

 - Hugh Dickins reworked compound page mapcount handling, simplifying it
   and making it more efficient

 - Removal of the autonuma savedwrite infrastructure from Nadav Amit and
   David Hildenbrand

 - zram support for multiple compression streams from Sergey Senozhatsky

 - David Hildenbrand reworked the GUP code's R/O long-term pinning so
   that drivers no longer need to use the FOLL_FORCE workaround which
   didn't work very well anyway

 - Mel Gorman altered the page allocator so that local IRQs can remnain
   enabled during per-cpu page allocations

 - Vishal Moola removed the try_to_release_page() wrapper

 - Stefan Roesch added some per-BDI sysfs tunables which are used to
   prevent network block devices from dirtying excessive amounts of
   pagecache

 - David Hildenbrand did some cleanup and repair work on KSM COW
   breaking

 - Nhat Pham and Johannes Weiner have implemented writeback in zswap's
   zsmalloc backend

 - Brian Foster has fixed a longstanding corner-case oddity in
   file[map]_write_and_wait_range()

 - sparse-vmemmap changes for MIPS, LoongArch and NIOS2 from Feiyang
   Chen

 - Shiyang Ruan has done some work on fsdax, to make its reflink mode
   work better under xfstests. Better, but still not perfect

 - Christoph Hellwig has removed the .writepage() method from several
   filesystems. They only need .writepages()

 - Yosry Ahmed wrote a series which fixes the memcg reclaim target
   beancounting

 - David Hildenbrand has fixed some of our MM selftests for 32-bit
   machines

 - Many singleton patches, as usual

* tag 'mm-stable-2022-12-13' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (313 commits)
  mm/hugetlb: set head flag before setting compound_order in __prep_compound_gigantic_folio
  mm: mmu_gather: allow more than one batch of delayed rmaps
  mm: fix typo in struct pglist_data code comment
  kmsan: fix memcpy tests
  mm: add cond_resched() in swapin_walk_pmd_entry()
  mm: do not show fs mm pc for VM_LOCKONFAULT pages
  selftests/vm: ksm_functional_tests: fixes for 32bit
  selftests/vm: cow: fix compile warning on 32bit
  selftests/vm: madv_populate: fix missing MADV_POPULATE_(READ|WRITE) definitions
  mm/gup_test: fix PIN_LONGTERM_TEST_READ with highmem
  mm,thp,rmap: fix races between updates of subpages_mapcount
  mm: memcg: fix swapcached stat accounting
  mm: add nodes= arg to memory.reclaim
  mm: disable top-tier fallback to reclaim on proactive reclaim
  selftests: cgroup: make sure reclaim target memcg is unprotected
  selftests: cgroup: refactor proactive reclaim code to reclaim_until()
  mm: memcg: fix stale protection of reclaim target memcg
  mm/mmap: properly unaccount memory on mas_preallocate() failure
  omfs: remove ->writepage
  jfs: remove ->writepage
  ...

Pull fuse update from Miklos Szeredi:

 - Allow some write requests to proceed in parallel

 - Fix a performance problem with allow_sys_admin_access

 - Add a special kind of invalidation that doesn't immediately purge
   submounts

 - On revalidation treat the target of rename(RENAME_NOREPLACE) the same
   as open(O_EXCL)

 - Use type safe helpers for some mnt_userns transformations

* tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: Rearrange fuse_allow_current_process checks
  fuse: allow non-extending parallel direct writes on the same file
  fuse: remove the unneeded result variable
  fuse: port to vfs{g,u}id_t and associated helpers
  fuse: Remove user_ns check for FUSE_DEV_IOC_CLONE
  fuse: always revalidate rename target dentry
  fuse: add "expire only" mode to FUSE_NOTIFY_INVAL_ENTRY
  fs/fuse: Replace kmap() with kmap_local_page()

Pull vfsuid updates from Christian Brauner:
 "Last cycle we introduced the vfs{g,u}id_t types and associated helpers
  to gain type safety when dealing with idmapped mounts. That initial
  work already converted a lot of places over but there were still some
  left,

  This converts all remaining places that still make use of non-type
  safe idmapping helpers to rely on the new type safe vfs{g,u}id based
  helpers.

  Afterwards it removes all the old non-type safe helpers"

* tag 'fs.vfsuid.conversion.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping:
  fs: remove unused idmapping helpers
  ovl: port to vfs{g,u}id_t and associated helpers
  fuse: port to vfs{g,u}id_t and associated helpers
  ima: use type safe idmapping helpers
  apparmor: use type safe idmapping helpers
  caps: use type safe idmapping helpers
  fs: use type safe idmapping helpers
  mnt_idmapping: add missing helpers

Pull setgid inheritance updates from Christian Brauner:
 "This contains the work to make setgid inheritance consistent between
  modifying a file and when changing ownership or mode as this has been
  a repeated source of very subtle bugs. The gist is that we perform the
  same permission checks in the write path as we do in the ownership and
  mode changing paths after this series where we're currently doing
  different things.

  We've already made setgid inheritance a lot more consistent and
  reliable in the last releases by moving setgid stripping from the
  individual filesystems up into the vfs. This aims to make the logic
  even more consistent and easier to understand and also to fix
  long-standing overlayfs setgid inheritance bugs. Miklos was nice
  enough to just let me carry the trivial overlayfs patches from Amir
  too.

  Below is a more detailed explanation how the current difference in
  setgid handling lead to very subtle bugs exemplified via overlayfs
  which is a victim of the current rules. I hope this explains why I
  think taking the regression risk here is worth it.

  A long while ago I found a few setgid inheritance bugs in overlayfs in
  the write path in certain conditions. Amir recently picked this back
  up in [1] and I jumped on board to fix this more generally.

  On the surface all that overlayfs would need to fix setgid inheritance
  would be to call file_remove_privs() or file_modified() but actually
  that isn't enough because the setgid inheritance api is wildly
  inconsistent in that area.

  Before this pr setgid stripping in file_remove_privs()'s old
  should_remove_suid() helper was inconsistent with other parts of the
  vfs. Specifically, it only raises ATTR_KILL_SGID if the inode is
  S_ISGID and S_IXGRP but not if the inode isn't in the caller's groups
  and the caller isn't privileged over the inode although we require
  this already in setattr_prepare() and setattr_copy() and so all
  filesystem implement this requirement implicitly because they have to
  use setattr_{prepare,copy}() anyway.

  But the inconsistency shows up in setgid stripping bugs for overlayfs
  in xfstests (e.g., generic/673, generic/683, generic/685, generic/686,
  generic/687). For example, we test whether suid and setgid stripping
  works correctly when performing various write-like operations as an
  unprivileged user (fallocate, reflink, write, etc.):

      echo "Test 1 - qa_user, non-exec file $verb"
      setup_testfile
      chmod a+rws $junk_file
      commit_and_check "$qa_user" "$verb" 64k 64k

  The test basically creates a file with 6666 permissions. While the
  file has the S_ISUID and S_ISGID bits set it does not have the S_IXGRP
  set.

  On a regular filesystem like xfs what will happen is:

      sys_fallocate()
      -> vfs_fallocate()
         -> xfs_file_fallocate()
            -> file_modified()
               -> __file_remove_privs()
                  -> dentry_needs_remove_privs()
                     -> should_remove_suid()
                  -> __remove_privs()
                     newattrs.ia_valid = ATTR_FORCE | kill;
                     -> notify_change()
                        -> setattr_copy()

  In should_remove_suid() we can see that ATTR_KILL_SUID is raised
  unconditionally because the file in the test has S_ISUID set.

  But we also see that ATTR_KILL_SGID won't be set because while the
  file is S_ISGID it is not S_IXGRP (see above) which is a condition for
  ATTR_KILL_SGID being raised.

  So by the time we call notify_change() we have attr->ia_valid set to
  ATTR_KILL_SUID | ATTR_FORCE.

  Now notify_change() sees that ATTR_KILL_SUID is set and does:

      ia_valid      = attr->ia_valid |= ATTR_MODE
      attr->ia_mode = (inode->i_mode & ~S_ISUID);

  which means that when we call setattr_copy() later we will definitely
  update inode->i_mode. Note that attr->ia_mode still contains S_ISGID.

  Now we call into the filesystem's ->setattr() inode operation which
  will end up calling setattr_copy(). Since ATTR_MODE is set we will
  hit:

      if (ia_valid & ATTR_MODE) {
              umode_t mode = attr->ia_mode;
              vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
              if (!vfsgid_in_group_p(vfsgid) &&
                  !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
                      mode &= ~S_ISGID;
              inode->i_mode = mode;
      }

  and since the caller in the test is neither capable nor in the group
  of the inode the S_ISGID bit is stripped.

  But assume the file isn't suid then ATTR_KILL_SUID won't be raised
  which has the consequence that neither the setgid nor the suid bits
  are stripped even though it should be stripped because the inode isn't
  in the caller's groups and the caller isn't privileged over the inode.

  If overlayfs is in the mix things become a bit more complicated and
  the bug shows up more clearly.

  When e.g., ovl_setattr() is hit from ovl_fallocate()'s call to
  file_remove_privs() then ATTR_KILL_SUID and ATTR_KILL_SGID might be
  raised but because the check in notify_change() is questioning the
  ATTR_KILL_SGID flag again by requiring S_IXGRP for it to be stripped
  the S_ISGID bit isn't removed even though it should be stripped:

      sys_fallocate()
      -> vfs_fallocate()
         -> ovl_fallocate()
            -> file_remove_privs()
               -> dentry_needs_remove_privs()
                  -> should_remove_suid()
               -> __remove_privs()
                  newattrs.ia_valid = ATTR_FORCE | kill;
                  -> notify_change()
                     -> ovl_setattr()
                        /* TAKE ON MOUNTER'S CREDS */
                        -> ovl_do_notify_change()
                           -> notify_change()
                        /* GIVE UP MOUNTER'S CREDS */
           /* TAKE ON MOUNTER'S CREDS */
           -> vfs_fallocate()
              -> xfs_file_fallocate()
                 -> file_modified()
                    -> __file_remove_privs()
                       -> dentry_needs_remove_privs()
                          -> should_remove_suid()
                       -> __remove_privs()
                          newattrs.ia_valid = attr_force | kill;
                          -> notify_change()

  The fix for all of this is to make file_remove_privs()'s
  should_remove_suid() helper perform the same checks as we already
  require in setattr_prepare() and setattr_copy() and have
  notify_change() not pointlessly requiring S_IXGRP again. It doesn't
  make any sense in the first place because the caller must calculate
  the flags via should_remove_suid() anyway which would raise
  ATTR_KILL_SGID

  Note that some xfstests will now fail as these patches will cause the
  setgid bit to be lost in certain conditions for unprivileged users
  modifying a setgid file when they would've been kept otherwise. I
  think this risk is worth taking and I explained and mentioned this
  multiple times on the list [2].

  Enforcing the rules consistently across write operations and
  chmod/chown will lead to losing the setgid bit in cases were it
  might've been retained before.

  While I've mentioned this a few times but it's worth repeating just to
  make sure that this is understood. For the sake of maintainability,
  consistency, and security this is a risk worth taking.

  If we really see regressions for workloads the fix is to have special
  setgid handling in the write path again with different semantics from
  chmod/chown and possibly additional duct tape for overlayfs. I'll
  update the relevant xfstests with if you should decide to merge this
  second setgid cleanup.

  Before that people should be aware that there might be failures for
  fstests where unprivileged users modify a setgid file"

Link: https://lore.kernel.org/linux-fsdevel/20221003123040.900827-1-amir73il@gmail.com [1]
Link: https://lore.kernel.org/linux-fsdevel/20221122142010.zchf2jz2oymx55qi@wittgenstein [2]

* tag 'fs.ovl.setgid.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping:
  fs: use consistent setgid checks in is_sxid()
  ovl: remove privs in ovl_fallocate()
  ovl: remove privs in ovl_copyfile()
  attr: use consistent sgid stripping checks
  attr: add setattr_should_drop_sgid()
  fs: move should_remove_suid()
  attr: add in_group_or_capable()

Pull VFS acl updates from Christian Brauner:
 "This contains the work that builds a dedicated vfs posix acl api.

  The origins of this work trace back to v5.19 but it took quite a while
  to understand the various filesystem specific implementations in
  sufficient detail and also come up with an acceptable solution.

  As we discussed and seen multiple times the current state of how posix
  acls are handled isn't nice and comes with a lot of problems: The
  current way of handling posix acls via the generic xattr api is error
  prone, hard to maintain, and type unsafe for the vfs until we call
  into the filesystem's dedicated get and set inode operations.

  It is already the case that posix acls are special-cased to death all
  the way through the vfs. There are an uncounted number of hacks that
  operate on the uapi posix acl struct instead of the dedicated vfs
  struct posix_acl. And the vfs must be involved in order to interpret
  and fixup posix acls before storing them to the backing store, caching
  them, reporting them to userspace, or for permission checking.

  Currently a range of hacks and duct tape exist to make this work. As
  with most things this is really no ones fault it's just something that
  happened over time. But the code is hard to understand and difficult
  to maintain and one is constantly at risk of introducing bugs and
  regressions when having to touch it.

  Instead of continuing to hack posix acls through the xattr handlers
  this series builds a dedicated posix acl api solely around the get and
  set inode operations.

  Going forward, the vfs_get_acl(), vfs_remove_acl(), and vfs_set_acl()
  helpers must be used in order to interact with posix acls. They
  operate directly on the vfs internal struct posix_acl instead of
  abusing the uapi posix acl struct as we currently do. In the end this
  removes all of the hackiness, makes the codepaths easier to maintain,
  and gets us type safety.

  This series passes the LTP and xfstests suites without any
  regressions. For xfstests the following combinations were tested:
   - xfs
   - ext4
   - btrfs
   - overlayfs
   - overlayfs on top of idmapped mounts
   - orangefs
   - (limited) cifs

  There's more simplifications for posix acls that we can make in the
  future if the basic api has made it.

  A few implementation details:

   - The series makes sure to retain exactly the same security and
     integrity module permission checks. Especially for the integrity
     modules this api is a win because right now they convert the uapi
     posix acl struct passed to them via a void pointer into the vfs
     struct posix_acl format to perform permission checking on the mode.

     There's a new dedicated security hook for setting posix acls which
     passes the vfs struct posix_acl not a void pointer. Basing checking
     on the posix acl stored in the uapi format is really unreliable.
     The vfs currently hacks around directly in the uapi struct storing
     values that frankly the security and integrity modules can't
     correctly interpret as evidenced by bugs we reported and fixed in
     this area. It's not necessarily even their fault it's just that the
     format we provide to them is sub optimal.

   - Some filesystems like 9p and cifs need access to the dentry in
     order to get and set posix acls which is why they either only
     partially or not even at all implement get and set inode
     operations. For example, cifs allows setxattr() and getxattr()
     operations but doesn't allow permission checking based on posix
     acls because it can't implement a get acl inode operation.

     Thus, this patch series updates the set acl inode operation to take
     a dentry instead of an inode argument. However, for the get acl
     inode operation we can't do this as the old get acl method is
     called in e.g., generic_permission() and inode_permission(). These
     helpers in turn are called in various filesystem's permission inode
     operation. So passing a dentry argument to the old get acl inode
     operation would amount to passing a dentry to the permission inode
     operation which we shouldn't and probably can't do.

     So instead of extending the existing inode operation Christoph
     suggested to add a new one. He also requested to ensure that the
     get and set acl inode operation taking a dentry are consistently
     named. So for this version the old get acl operation is renamed to
     ->get_inode_acl() and a new ->get_acl() inode operation taking a
     dentry is added. With this we can give both 9p and cifs get and set
     acl inode operations and in turn remove their complex custom posix
     xattr handlers.

     In the future I hope to get rid of the inode method duplication but
     it isn't like we have never had this situation. Readdir is just one
     example. And frankly, the overall gain in type safety and the more
     pleasant api wise are simply too big of a benefit to not accept
     this duplication for a while.

   - We've done a full audit of every codepaths using variant of the
     current generic xattr api to get and set posix acls and
     surprisingly it isn't that many places. There's of course always a
     chance that we might have missed some and if so I'm sure we'll find
     them soon enough.

     The crucial codepaths to be converted are obviously stacking
     filesystems such as ecryptfs and overlayfs.

     For a list of all callers currently using generic xattr api helpers
     see [2] including comments whether they support posix acls or not.

   - The old vfs generic posix acl infrastructure doesn't obey the
     create and replace semantics promised on the setxattr(2) manpage.
     This patch series doesn't address this. It really is something we
     should revisit later though.

  The patches are roughly organized as follows:

   (1) Change existing set acl inode operation to take a dentry
       argument (Intended to be a non-functional change)

   (2) Rename existing get acl method (Intended to be a non-functional
       change)

   (3) Implement get and set acl inode operations for filesystems that
       couldn't implement one before because of the missing dentry.
       That's mostly 9p and cifs (Intended to be a non-functional
       change)

   (4) Build posix acl api, i.e., add vfs_get_acl(), vfs_remove_acl(),
       and vfs_set_acl() including security and integrity hooks
       (Intended to be a non-functional change)

   (5) Implement get and set acl inode operations for stacking
       filesystems (Intended to be a non-functional change)

   (6) Switch posix acl handling in stacking filesystems to new posix
       acl api now that all filesystems it can stack upon support it.

   (7) Switch vfs to new posix acl api (semantical change)

   (8) Remove all now unused helpers

   (9) Additional regression fixes reported after we merged this into
       linux-next

  Thanks to Seth for a lot of good discussion around this and
  encouragement and input from Christoph"

* tag 'fs.acl.rework.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: (36 commits)
  posix_acl: Fix the type of sentinel in get_acl
  orangefs: fix mode handling
  ovl: call posix_acl_release() after error checking
  evm: remove dead code in evm_inode_set_acl()
  cifs: check whether acl is valid early
  acl: make vfs_posix_acl_to_xattr() static
  acl: remove a slew of now unused helpers
  9p: use stub posix acl handlers
  cifs: use stub posix acl handlers
  ovl: use stub posix acl handlers
  ecryptfs: use stub posix acl handlers
  evm: remove evm_xattr_acl_change()
  xattr: use posix acl api
  ovl: use posix acl api
  ovl: implement set acl method
  ovl: implement get acl method
  ecryptfs: implement set acl method
  ecryptfs: implement get acl method
  ksmbd: use vfs_remove_acl()
  acl: add vfs_remove_acl()
  ...

Pull iov_iter updates from Al Viro:
 "iov_iter work; most of that is about getting rid of direction
  misannotations and (hopefully) preventing more of the same for the
  future"

* tag 'pull-iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  use less confusing names for iov_iter direction initializers
  iov_iter: saner checks for attempt to copy to/from iterator
  [xen] fix "direction" argument of iov_iter_kvec()
  [vhost] fix 'direction' argument of iov_iter_{init,bvec}()
  [target] fix iov_iter_bvec() "direction" argument
  [s390] memcpy_real(): WRITE is "data source", not destination...
  [s390] zcore: WRITE is "data source", not destination...
  [infiniband] READ is "data destination", not source...
  [fsi] WRITE is "data source", not destination...
  [s390] copy_oldmem_kernel() - WRITE is "data source", not destination
  csum_and_copy_to_iter(): handle ITER_DISCARD
  get rid of unlikely() on page_copy_sane() calls

Converts the function to try to move folios instead of pages. Also
converts fuse_check_page() to fuse_get_folio() since this is its only
caller. This change removes 15 calls to compound_head().

Link: https://lkml.kernel.org/r/20221101175326.13265-3-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "Removing the lru_cache_add() wrapper".

This patchset replaces all calls of lru_cache_add() with the folio
equivalent: folio_add_lru().  This is allows us to get rid of the wrapper
The series passes xfstests and the userfaultfd selftests.


This patch (of 5):

Eliminates 7 calls to compound_head().

Link: https://lkml.kernel.org/r/20221101175326.13265-1-vishal.moola@gmail.com
Link: https://lkml.kernel.org/r/20221101175326.13265-2-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

READ/WRITE proved to be actively confusing - the meanings are
"data destination, as used with read(2)" and "data source, as
used with write(2)", but people keep interpreting those as
"we read data from it" and "we write data to it", i.e. exactly
the wrong way.

Call them ITER_DEST and ITER_SOURCE - at least that is harder
to misinterpret...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>