Since 2002 (change "Replace BKL for chain locking with sysvfs-private
rwlock") the sysv filesystem was doing IO under a rwlock in its
get_block() function (yes, a non-sleepable lock hold over a function
used to read inode metadata for all reads and writes).  Nobody noticed
until syzbot in 2023 [1]. This shows nobody is using the filesystem.
Just drop it.

[1] https://lore.kernel.org/all/0000000000000ccf9a05ee84f5b0@google.com/

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20250220163940.10155-2-jack@suse.cz
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Match ext2 and remove a few hidden calls to compound_head().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

This matches ext2 and removes a few hidden calls to compound_head().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Remove a few hidden calls to compound_head().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

In later patches, we're going to change how the inode's ctime field is
used. Switch to using accessor functions instead of raw accesses of
inode->i_ctime.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230705190309.579783-74-jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

With commit 849ad04cf562a ("new helper: put_and_unmap_page()"), Al Viro
introduced the put_and_unmap_page() to use in those many places where we
have a common pattern consisting of calls to kunmap_local() +
put_page().

Obviously, first we unmap and then we put pages. Instead, the original
name of this helper seems to imply that we first put and then unmap.

Therefore, rename the helper and change the only known upstreamed user
(i.e., fs/sysv) before this helper enters common use and might become
difficult to find all call sites and instead easy to break the builds.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Message-Id: <20230602103307.5637-1-fmdefrancesco@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

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

Pull sysv updates from Al Viro:
 "Fabio's 'switch to kmap_local_page()' patchset (originally after the
  ext2 counterpart, with a lot of cleaning up done to it; as the matter
  of fact, ext2 side is in need of similar cleanups - calling
  conventions there are bloody awful).

  Plus the equivalents of minix stuff..."

* 'work.sysv' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  sysv: fix handling of delete_entry and set_link failures
  fs/sysv: Replace kmap() with kmap_local_page()
  fs/sysv: Use dir_put_page() in sysv_rename()
  fs/sysv: Change the signature of dir_get_page()
  fs/sysv: Use the offset_in_page() helper
  sysv: don't flush page immediately for DIRSYNC directories

similar to minixfs series - make sysv_set_link() report failures,
lift dir_put_page() into the callers of sysv_set_link() and
sysv_delete_entry(), make sysv_rename() handle failures in both.

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

kmap() is being deprecated in favor of kmap_local_page().

There are two main problems with kmap(): (1) It comes with an overhead as
the mapping space is restricted and protected by a global lock for
synchronization and (2) it also requires global TLB invalidation when the
kmap’s pool wraps and it might block when the mapping space is fully
utilized until a slot becomes available.

With kmap_local_page() the mappings are per thread, CPU local, can take
page faults, and can be called from any context (including interrupts).
It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore,
the tasks can be preempted and, when they are scheduled to run again, the
kernel virtual addresses are restored and still valid.

Since kmap_local_page() would not break the strict rules of local mappings
(i.e., the thread locality and the stack based nesting), this function can
be easily and safely replace the deprecated API.

Therefore, replace kmap() with kmap_local_page() in fs/sysv. kunmap_local()
requires the mapping address, so return that address from dir_get_page()
to be used in dir_put_page().

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>