linux.git/fs/ext4/file.c, branch v4.5

ext2, ext4: fix issue with missing journal entry in ext4_dax_mkwrite()

2016-02-27T19:01:16+00:00

As it is currently written ext4_dax_mkwrite() assumes that the call into
__dax_mkwrite() will not have to do a block allocation so it doesn't create
a journal entry.  For a read that creates a zero page to cover a hole
followed by a write that actually allocates storage this is incorrect.  The
ext4_dax_mkwrite() -> __dax_mkwrite() -> __dax_fault() path calls
get_blocks() to allocate storage.

Fix this by having the ->page_mkwrite fault handler call ext4_dax_fault()
as this function already has all the logic needed to allocate a journal
entry and call __dax_fault().

Also update the ext2 fault handlers in this same way to remove duplicate
code and keep the logic between ext2 and ext4 the same.

Reviewed-by: Jan Kara 
Signed-off-by: Ross Zwisler 
Signed-off-by: Theodore Ts'o

ext4 crypto: move context consistency check to ext4_file_open()

2016-02-08T05:54:26+00:00

In the case where the per-file key for the directory is cached, but
root does not have access to the key needed to derive the per-file key
for the files in the directory, we allow the lookup to succeed, so
that lstat(2) and unlink(2) can suceed.  However, if a program tries
to open the file, it will get an ENOKEY error.

Signed-off-by: Theodore Ts'o

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2016-01-23T20:24:56+00:00

Pull final vfs updates from Al Viro:

 - The ->i_mutex wrappers (with small prereq in lustre)

 - a fix for too early freeing of symlink bodies on shmem (they need to
   be RCU-delayed) (-stable fodder)

 - followup to dedupe stuff merged this cycle

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: abort dedupe loop if fatal signals are pending
  make sure that freeing shmem fast symlinks is RCU-delayed
  wrappers for ->i_mutex access
  lustre: remove unused declaration

ext4: call dax_pfn_mkwrite() for DAX fsync/msync

2016-01-23T01:02:18+00:00

To properly support the new DAX fsync/msync infrastructure filesystems
need to call dax_pfn_mkwrite() so that DAX can track when user pages are
dirtied.

Signed-off-by: Ross Zwisler 
Cc: "H. Peter Anvin" 
Cc: "J. Bruce Fields" 
Cc: "Theodore Ts'o" 
Cc: Alexander Viro 
Cc: Andreas Dilger 
Cc: Dave Chinner 
Cc: Ingo Molnar 
Cc: Jan Kara 
Cc: Jeff Layton 
Cc: Matthew Wilcox 
Cc: Thomas Gleixner 
Cc: Dan Williams 
Cc: Matthew Wilcox 
Cc: Dave Hansen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

wrappers for ->i_mutex access

2016-01-22T23:04:28+00:00

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro

ext4: use pre-zeroed blocks for DAX page faults

2015-12-07T20:10:44+00:00

Make DAX fault path use pre-zeroed blocks to avoid races with extent
conversion and zeroing when two page faults to the same block happen.

Signed-off-by: Jan Kara 
Signed-off-by: Theodore Ts'o

ext4: fix races between page faults and hole punching

2015-12-07T19:28:03+00:00

Currently, page faults and hole punching are completely unsynchronized.
This can result in page fault faulting in a page into a range that we
are punching after truncate_pagecache_range() has been called and thus
we can end up with a page mapped to disk blocks that will be shortly
freed. Filesystem corruption will shortly follow. Note that the same
race is avoided for truncate by checking page fault offset against
i_size but there isn't similar mechanism available for punching holes.

Fix the problem by creating new rw semaphore i_mmap_sem in inode and
grab it for writing over truncate, hole punching, and other functions
removing blocks from extent tree and for read over page faults. We
cannot easily use i_data_sem for this since that ranks below transaction
start and we need something ranking above it so that it can be held over
the whole truncate / hole punching operation. Also remove various
workarounds we had in the code to reduce race window when page fault
could have created pages with stale mapping information.

Signed-off-by: Jan Kara 
Signed-off-by: Theodore Ts'o

ext4: start transaction before calling into DAX

2015-09-08T22:35:28+00:00

Jan Kara pointed out that in the case where we are writing to a hole, we
can end up with a lock inversion between the page lock and the journal
lock.  We can avoid this by starting the transaction in ext4 before
calling into DAX.  The journal lock nests inside the superblock
pagefault lock, so we have to duplicate that code from dax_fault, like
XFS does.

Signed-off-by: Matthew Wilcox 
Cc: Jan Kara 
Cc: Theodore Ts'o 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ext4: add ext4_get_block_dax()

2015-09-08T22:35:28+00:00

DAX wants different semantics from any currently-existing ext4 get_block
callback.  Unlike ext4_get_block_write(), it needs to honour the
'create' flag, and unlike ext4_get_block(), it needs to be able to
return unwritten extents.  So introduce a new ext4_get_block_dax() which
has those semantics.

We could also change ext4_get_block_write() to honour the 'create' flag,
but that might have consequences on other users that I do not currently
understand.

Signed-off-by: Matthew Wilcox 
Cc: Theodore Ts'o 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ext4: use ext4_get_block_write() for DAX

2015-09-08T22:35:28+00:00

DAX relies on the get_block function either zeroing newly allocated
blocks before they're findable by subsequent calls to get_block, or
marking newly allocated blocks as unwritten.  ext4_get_block() cannot
create unwritten extents, but ext4_get_block_write() can.

Signed-off-by: Matthew Wilcox 
Reported-by: Andy Rudoff 
Cc: Theodore Ts'o 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds