linux.git/fs/super.c, branch v5.12.5

Merge tag 'docs-5.12' of git://git.lwn.net/linux

2021-02-22T18:57:46+00:00

Pull documentation updates from Jonathan Corbet:
 "It has been a relatively quiet cycle in docsland.

   - As promised, the minimum Sphinx version to build the docs is now
     1.7, and we have dropped support for Python 2 entirely. That
     allowed the removal of a bunch of compatibility code.

   - A set of treewide warning fixups from Mauro that I applied after it
     became clear nobody else was going to deal with them.

   - The automarkup mechanism can now create cross-references from
     relative paths to RST files.

   - More translations, typo fixes, and warning fixes"

* tag 'docs-5.12' of git://git.lwn.net/linux: (75 commits)
  docs: kernel-hacking: be more civil
  docs: Remove the Microsoft rhetoric
  Documentation/admin-guide: kernel-parameters: Update nohlt section
  doc/admin-guide: fix spelling mistake: "perfomance" -> "performance"
  docs: Document cross-referencing using relative path
  docs: Enable usage of relative paths to docs on automarkup
  docs: thermal: fix spelling mistakes
  Documentation: admin-guide: Update kvm/xen config option
  docs: Make syscalls' helpers naming consistent
  coding-style.rst: Avoid comma statements
  Documentation: /proc/loadavg: add 3 more field descriptions
  Documentation/submitting-patches: Add blurb about backtraces in commit messages
  Docs: drop Python 2 support
  Move our minimum Sphinx version to 1.7
  Documentation: input: define ABS_PRESSURE/ABS_MT_PRESSURE resolution as grams
  scripts/kernel-doc: add internal hyperlink to DOC: sections
  Update Documentation/admin-guide/sysctl/fs.rst
  docs: Update DTB format references
  docs: zh_CN: add iio index.rst translation
  docs/zh_CN: add iio ep93xx_adc.rst translation
  ...

block: remove the NULL bdev check in bdev_read_only

2021-01-25T01:15:57+00:00

Only a single caller can end up in bdev_read_only, so move the check
there.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Ming Lei 
Reviewed-by: Martin K. Petersen 
Reviewed-by: Hannes Reinecke 
Signed-off-by: Jens Axboe

fs: fix kernel-doc markups

2021-01-21T21:06:00+00:00

Two markups are at the wrong place. Kernel-doc only
support having the comment just before the identifier.

Also, some identifiers have different names between their
prototypes and the kernel-doc markup.

Signed-off-by: Mauro Carvalho Chehab 
Link: https://lore.kernel.org/r/96b1e1b388600ab092331f6c4e88ff8e8779ce6c.1610610937.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet

block: remove i_bdev

2020-12-01T21:53:39+00:00

Switch the block device lookup interfaces to directly work with a dev_t
so that struct block_device references are only acquired by the
blkdev_get variants (and the blk-cgroup special case).  This means that
we now don't need an extra reference in the inode and can generally
simplify handling of struct block_device to keep the lookups contained
in the core block layer code.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Reviewed-by: Hannes Reinecke 
Acked-by: Tejun Heo 
Acked-by: Coly Li 		[bcache]
Signed-off-by: Jens Axboe

fs: remove get_super_thawed and get_super_exclusive_thawed

2020-12-01T21:53:38+00:00

Just open code the wait in the only caller of both functions.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Reviewed-by: Hannes Reinecke 
Signed-off-by: Jens Axboe

vfs: move __sb_{start,end}_write* to fs.h

2020-11-11T00:53:11+00:00

Now that we've straightened out the callers, move these three functions
to fs.h since they're fairly trivial.

Signed-off-by: Darrick J. Wong 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara

vfs: separate __sb_start_write into blocking and non-blocking helpers

2020-11-11T00:53:07+00:00

Break this function into two helpers so that it's obvious that the
trylock versions return a value that must be checked, and the blocking
versions don't require that.  While we're at it, clean up the return
type mismatch.

Signed-off-by: Darrick J. Wong 
Reviewed-by: Jan Kara 
Reviewed-by: Christoph Hellwig

vfs: remove lockdep bogosity in __sb_start_write

2020-11-11T00:49:29+00:00

__sb_start_write has some weird looking lockdep code that claims to
exist to handle nested freeze locking requests from xfs.  The code as
written seems broken -- if we think we hold a read lock on any of the
higher freeze levels (e.g. we hold SB_FREEZE_WRITE and are trying to
lock SB_FREEZE_PAGEFAULT), it converts a blocking lock attempt into a
trylock.

However, it's not correct to downgrade a blocking lock attempt to a
trylock unless the downgrading code or the callers are prepared to deal
with that situation.  Neither __sb_start_write nor its callers handle
this at all.  For example:

sb_start_pagefault ignores the return value completely, with the result
that if xfs_filemap_fault loses a race with a different thread trying to
fsfreeze, it will proceed without pagefault freeze protection (thereby
breaking locking rules) and then unlocks the pagefault freeze lock that
it doesn't own on its way out (thereby corrupting the lock state), which
leads to a system hang shortly afterwards.

Normally, this won't happen because our ownership of a read lock on a
higher freeze protection level blocks fsfreeze from grabbing a write
lock on that higher level.  *However*, if lockdep is offline,
lock_is_held_type unconditionally returns 1, which means that
percpu_rwsem_is_held returns 1, which means that __sb_start_write
unconditionally converts blocking freeze lock attempts into trylocks,
even when we *don't* hold anything that would block a fsfreeze.

Apparently this all held together until 5.10-rc1, when bugs in lockdep
caused lockdep to shut itself off early in an fstests run, and once
fstests gets to the "race writes with freezer" tests, kaboom.  This
might explain the long trail of vanishingly infrequent livelocks in
fstests after lockdep goes offline that I've never been able to
diagnose.

We could fix it by spinning on the trylock if wait==true, but AFAICT the
locking works fine if lockdep is not built at all (and I didn't see any
complaints running fstests overnight), so remove this snippet entirely.

NOTE: Commit f4b554af9931 in 2015 created the current weird logic (which
used to exist in a different form in commit 5accdf82ba25c from 2012) in
__sb_start_write.  XFS solved this whole problem in the late 2.6 era by
creating a variant of transactions (XFS_TRANS_NO_WRITECOUNT) that don't
grab intwrite freeze protection, thus making lockdep's solution
unnecessary.  The commit claims that Dave Chinner explained that the
trylock hack + comment could be removed, but nobody ever did.

Signed-off-by: Darrick J. Wong 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara

bdi: replace BDI_CAP_STABLE_WRITES with a queue and a sb flag

2020-09-24T19:43:39+00:00

The BDI_CAP_STABLE_WRITES is one of the few bits of information in the
backing_dev_info shared between the block drivers and the writeback code.
To help untangling the dependency replace it with a queue flag and a
superblock flag derived from it.  This also helps with the case of e.g.
a file system requiring stable writes due to its own checksumming, but
not forcing it on other users of the block device like the swap code.

One downside is that we an't support the stable_pages_required bdi
attribute in sysfs anymore.  It is replaced with a queue attribute which
also is writable for easier testing.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Reviewed-by: Johannes Thumshirn 
Signed-off-by: Jens Axboe

Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2020-06-10T23:09:11+00:00

Pull vfs fixes from Al Viro:
 "A couple of trivial patches that fell through the cracks last cycle"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: fix indentation in deactivate_super()
  vfs: Remove duplicated d_mountpoint check in __is_local_mountpoint