In preparation for consulting a badblocks list in pmem_direct_access(),
teach dax_pmd_fault() to fallback rather than fail immediately upon
encountering an error.  The thought being that reducing the span of the
dax request may avoid the error region.
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

blkdev_dax_capable() is similar to bdev_dax_supported(), but needs
to remain as a separate interface for checking dax capability of
a raw block device.

Rename and relocate blkdev_dax_capable() to keep them maintained
consistently, and call bdev_direct_access() for the dax capability
check.

There is no change in the behavior.

Link: https://lkml.org/lkml/2016/5/9/950Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@fb.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

When a partition is not aligned by 4KB, mount -o dax succeeds,
but any read/write access to the filesystem fails, except for
metadata update.

Call bdev_dax_supported() to perform proper precondition checks
which includes this partition alignment check.
Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

When a partition is not aligned by 4KB, mount -o dax succeeds,
but any read/write access to the filesystem fails, except for
metadata update.

Call bdev_dax_supported() to perform proper precondition checks
which includes this partition alignment check.
Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

When a partition is not aligned by 4KB, mount -o dax succeeds,
but any read/write access to the filesystem fails, except for
metadata update.

Call bdev_dax_supported() to perform proper precondition checks
which includes this partition alignment check.
Reported-by: NMicah Parrish <micah.parrish@hpe.com>
Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

DAX imposes additional requirements to a device.  Add
bdev_dax_supported() which performs all the precondition checks
necessary for filesystem to mount the device with dax option.

Also add a new check to verify if a partition is aligned by 4KB.
When a partition is unaligned, any dax read/write access fails,
except for metadata update.
Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@fb.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

In preparation of moving DAX capability checks to the block layer
from filesystem code, add a VFS message interface that aligns with
filesystem's message format.

For instance, a vfs_msg() message followed by XFS messages in case
of a dax mount error may look like:

  VFS (pmem0p1): error: unaligned partition for dax
  XFS (pmem0p1): DAX unsupported by block device. Turning off DAX.
  XFS (pmem0p1): Mounting V5 Filesystem
   :

vfs_msg() is largely based on ext4_msg().
Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@fb.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

Callers of dax fault handlers must make sure these calls cannot race
with truncate. Thus it is enough to check inode size when entering the
function and we don't have to recheck it again later in the handler.
Note that inode size itself can be decreased while the fault handler
runs but filesystem locking prevents against any radix tree or block
mapping information changes resulting from the truncate and that is what
we really care about.
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

dax_do_io() is calling filemap_write_and_wait() if DIO_LOCKING flags is
set. Presumably this was copied over from direct IO code. However DAX
inodes have no pagecache pages to write so the call is pointless. Remove
it.
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

All the filesystems are now zeroing blocks themselves for DAX IO to avoid
races between dax_io() and dax_fault(). Remove the zeroing code from
dax_io() and add warning to catch the case when somebody unexpectedly
returns new or unwritten buffer.
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

Now that all filesystems zero out blocks allocated for a fault handler,
we can just remove the zeroing from the handler itself. Also add checks
that no filesystem returns to us unwritten or new buffer.
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

Currently ext2 zeroes any data blocks allocated for DAX inode however it
still returns them as BH_New. Thus DAX code zeroes them again in
dax_insert_mapping() which can possibly overwrite the data that has been
already stored to those blocks by a racing dax_io(). Avoid marking
pre-zeroed buffers as new.
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

When zeroing allocated blocks for DAX, we accidentally zeroed only the
first allocated block instead of all of them. So far this problem is
hidden by the fact that page faults always need only a single block and
DAX write code zeroes blocks again. But the zeroing in DAX code is racy
and needs to be removed so fix the zeroing in ext2 to zero all allocated
blocks.
Reported-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

Fault handlers currently take complete_unwritten argument to convert
unwritten extents after PTEs are updated. However no filesystem uses
this anymore as the code is racy. Remove the unused argument.
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

These don't belong in radix-tree.c any more than PAGECACHE_TAG_* do.
Let's try to maintain the idea that radix-tree simply implements an
abstract data type.
Acked-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: NMatthew Wilcox <willy@linux.intel.com>
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>

Currently ext4 treats DAX IO the same way as direct IO. I.e., it
allocates unwritten extents before IO is done and converts unwritten
extents afterwards. However this way DAX IO can race with page fault to
the same area:

ext4_ext_direct_IO()				dax_fault()
  dax_io()
    get_block() - allocates unwritten extent
    copy_from_iter_pmem()
						  get_block() - converts
						    unwritten block to
						    written and zeroes it
						    out
  ext4_convert_unwritten_extents()

So data written with DAX IO gets lost. Similarly dax_new_buf() called
from dax_io() can overwrite data that has been already written to the
block via mmap.

Fix the problem by using pre-zeroed blocks for DAX IO the same way as we
use them for DAX mmap. The downside of this solution is that every
allocating write writes each block twice (once zeros, once data). Fixing
the race with locking is possible as well however we would need to
lock-out faults for the whole range written to by DAX IO. And that is
not easy to do without locking-out faults for the whole file which seems
too aggressive.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently ext4 direct IO handling is split between ext4_ext_direct_IO()
and ext4_ind_direct_IO(). However the extent based function calls into
the indirect based one for some cases and for example it is not able to
handle file extending. Previously it was not also properly handling
retries in case of ENOSPC errors. With DAX things would get even more
contrieved so just refactor the direct IO code and instead of indirect /
extent split do the split to read vs writes.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

When there are blocks to free in the running transaction, block
allocator can return ENOSPC although the filesystem has some blocks to
free. We use ext4_should_retry_alloc() to force commit of the current
transaction and return whether anything was committed so that it makes
sense to retry the allocation. However the transaction may get committed
after block allocation fails but before we call
ext4_should_retry_alloc(). So ext4_should_retry_alloc() returns false
because there is nothing to commit and we wrongly return ENOSPC.

Fix the race by unconditionally returning 1 from ext4_should_retry_alloc()
when we tried to commit a transaction. This should not add any
unnecessary retries since we had a transaction running a while ago when
trying to allocate blocks and we want to retry the allocation once that
transaction has committed anyway.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

ext4_dax_get_blocks() was accidentally omitted fixing get blocks
handlers to properly handle transient ENOSPC errors. Fix it now to use
ext4_get_blocks_trans() helper which takes care of these errors.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently, __dax_fault() does not call get_blocks() callback with create
argument set, when we got back unwritten extent from the initial
get_blocks() call during a write fault. This is because originally
filesystems were supposed to convert unwritten extents to written ones
using complete_unwritten() callback. Later this was abandoned in favor of
using pre-zeroed blocks however the condition whether get_blocks() needs
to be called with create == 1 remained.

Fix the condition so that filesystems are not forced to zero-out and
convert unwritten extents when get_blocks() is called with create == 0
(which introduces unnecessary overhead for read faults and can be
problematic as the filesystem may possibly be read-only).
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

ext4_find_extent(), stripped down to the parts relevant to this patch,
reads as

  ppos = 0;
  i = depth;
  while (i) {
    --i;
    ++ppos;
    if (unlikely(ppos > depth)) {
      ...
      ret = -EFSCORRUPTED;
      goto err;
    }
  }

Due to the loop's bounds, the condition ppos > depth can never be met.

Remove this dead code.
Signed-off-by: NNicolai Stange <nicstange@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Commit bf699327 ("jbd2: Use tracepoints for history file")
removed the members j_history, j_history_max and j_history_cur from struct
handle_s but the descriptions stayed lingering. Removing them.
Signed-off-by: NLuis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>

ext4_io_submit() used to check for EOPNOTSUPP after bio submission,
which is why it had to get an extra reference to the bio before
submitting it. But since we no longer touch the bio after submission,
get rid of the redundant get/put of the bio. If we do get the extra
reference, we enter the slower path of having to flag this bio as now
having external references.
Signed-off-by: NJens Axboe <axboe@fb.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently, in ext4_mb_init(), there's a loop like the following:

  do {
    ...
    offset += 1 << (sb->s_blocksize_bits - i);
    i++;
  } while (i <= sb->s_blocksize_bits + 1);

Note that the updated offset is used in the loop's next iteration only.

However, at the last iteration, that is at i == sb->s_blocksize_bits + 1,
the shift count becomes equal to (unsigned)-1 > 31 (c.f. C99 6.5.7(3))
and UBSAN reports

  UBSAN: Undefined behaviour in fs/ext4/mballoc.c:2621:15
  shift exponent 4294967295 is too large for 32-bit type 'int'
  [...]
  Call Trace:
   [<ffffffff818c4d25>] dump_stack+0xbc/0x117
   [<ffffffff818c4c69>] ? _atomic_dec_and_lock+0x169/0x169
   [<ffffffff819411ab>] ubsan_epilogue+0xd/0x4e
   [<ffffffff81941cac>] __ubsan_handle_shift_out_of_bounds+0x1fb/0x254
   [<ffffffff81941ab1>] ? __ubsan_handle_load_invalid_value+0x158/0x158
   [<ffffffff814b6dc1>] ? kmem_cache_alloc+0x101/0x390
   [<ffffffff816fc13b>] ? ext4_mb_init+0x13b/0xfd0
   [<ffffffff814293c7>] ? create_cache+0x57/0x1f0
   [<ffffffff8142948a>] ? create_cache+0x11a/0x1f0
   [<ffffffff821c2168>] ? mutex_lock+0x38/0x60
   [<ffffffff821c23ab>] ? mutex_unlock+0x1b/0x50
   [<ffffffff814c26ab>] ? put_online_mems+0x5b/0xc0
   [<ffffffff81429677>] ? kmem_cache_create+0x117/0x2c0
   [<ffffffff816fcc49>] ext4_mb_init+0xc49/0xfd0
   [...]

Observe that the mentioned shift exponent, 4294967295, equals (unsigned)-1.

Unless compilers start to do some fancy transformations (which at least
GCC 6.0.0 doesn't currently do), the issue is of cosmetic nature only: the
such calculated value of offset is never used again.

Silence UBSAN by introducing another variable, offset_incr, holding the
next increment to apply to offset and adjust that one by right shifting it
by one position per loop iteration.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=114701
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=112161

Cc: stable@vger.kernel.org
Signed-off-by: NNicolai Stange <nicstange@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently, in mb_find_order_for_block(), there's a loop like the following:

  while (order <= e4b->bd_blkbits + 1) {
    ...
    bb += 1 << (e4b->bd_blkbits - order);
  }

Note that the updated bb is used in the loop's next iteration only.

However, at the last iteration, that is at order == e4b->bd_blkbits + 1,
the shift count becomes negative (c.f. C99 6.5.7(3)) and UBSAN reports

  UBSAN: Undefined behaviour in fs/ext4/mballoc.c:1281:11
  shift exponent -1 is negative
  [...]
  Call Trace:
   [<ffffffff818c4d35>] dump_stack+0xbc/0x117
   [<ffffffff818c4c79>] ? _atomic_dec_and_lock+0x169/0x169
   [<ffffffff819411bb>] ubsan_epilogue+0xd/0x4e
   [<ffffffff81941cbc>] __ubsan_handle_shift_out_of_bounds+0x1fb/0x254
   [<ffffffff81941ac1>] ? __ubsan_handle_load_invalid_value+0x158/0x158
   [<ffffffff816e93a0>] ? ext4_mb_generate_from_pa+0x590/0x590
   [<ffffffff816502c8>] ? ext4_read_block_bitmap_nowait+0x598/0xe80
   [<ffffffff816e7b7e>] mb_find_order_for_block+0x1ce/0x240
   [...]

Unless compilers start to do some fancy transformations (which at least
GCC 6.0.0 doesn't currently do), the issue is of cosmetic nature only: the
such calculated value of bb is never used again.

Silence UBSAN by introducing another variable, bb_incr, holding the next
increment to apply to bb and adjust that one by right shifting it by one
position per loop iteration.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=114701
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=112161

Cc: stable@vger.kernel.org
Signed-off-by: NNicolai Stange <nicstange@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

When filesystem is corrupted in the right way, it can happen
ext4_mark_iloc_dirty() in ext4_orphan_add() returns error and we
subsequently remove inode from the in-memory orphan list. However this
deletion is done with list_del(&EXT4_I(inode)->i_orphan) and thus we
leave i_orphan list_head with a stale content. Later we can look at this
content causing list corruption, oops, or other issues. The reported
trace looked like:

WARNING: CPU: 0 PID: 46 at lib/list_debug.c:53 __list_del_entry+0x6b/0x100()
list_del corruption, 0000000061c1d6e0->next is LIST_POISON1
0000000000100100)
CPU: 0 PID: 46 Comm: ext4.exe Not tainted 4.1.0-rc4+ #250
Stack:
 60462947 62219960 602ede24 62219960
 602ede24 603ca293 622198f0 602f02eb
 62219950 6002c12c 62219900 601b4d6b
Call Trace:
 [<6005769c>] ? vprintk_emit+0x2dc/0x5c0
 [<602ede24>] ? printk+0x0/0x94
 [<600190bc>] show_stack+0xdc/0x1a0
 [<602ede24>] ? printk+0x0/0x94
 [<602ede24>] ? printk+0x0/0x94
 [<602f02eb>] dump_stack+0x2a/0x2c
 [<6002c12c>] warn_slowpath_common+0x9c/0xf0
 [<601b4d6b>] ? __list_del_entry+0x6b/0x100
 [<6002c254>] warn_slowpath_fmt+0x94/0xa0
 [<602f4d09>] ? __mutex_lock_slowpath+0x239/0x3a0
 [<6002c1c0>] ? warn_slowpath_fmt+0x0/0xa0
 [<60023ebf>] ? set_signals+0x3f/0x50
 [<600a205a>] ? kmem_cache_free+0x10a/0x180
 [<602f4e88>] ? mutex_lock+0x18/0x30
 [<601b4d6b>] __list_del_entry+0x6b/0x100
 [<601177ec>] ext4_orphan_del+0x22c/0x2f0
 [<6012f27c>] ? __ext4_journal_start_sb+0x2c/0xa0
 [<6010b973>] ? ext4_truncate+0x383/0x390
 [<6010bc8b>] ext4_write_begin+0x30b/0x4b0
 [<6001bb50>] ? copy_from_user+0x0/0xb0
 [<601aa840>] ? iov_iter_fault_in_readable+0xa0/0xc0
 [<60072c4f>] generic_perform_write+0xaf/0x1e0
 [<600c4166>] ? file_update_time+0x46/0x110
 [<60072f0f>] __generic_file_write_iter+0x18f/0x1b0
 [<6010030f>] ext4_file_write_iter+0x15f/0x470
 [<60094e10>] ? unlink_file_vma+0x0/0x70
 [<6009b180>] ? unlink_anon_vmas+0x0/0x260
 [<6008f169>] ? free_pgtables+0xb9/0x100
 [<600a6030>] __vfs_write+0xb0/0x130
 [<600a61d5>] vfs_write+0xa5/0x170
 [<600a63d6>] SyS_write+0x56/0xe0
 [<6029fcb0>] ? __libc_waitpid+0x0/0xa0
 [<6001b698>] handle_syscall+0x68/0x90
 [<6002633d>] userspace+0x4fd/0x600
 [<6002274f>] ? save_registers+0x1f/0x40
 [<60028bd7>] ? arch_prctl+0x177/0x1b0
 [<60017bd5>] fork_handler+0x85/0x90

Fix the problem by using list_del_init() as we always should with
i_orphan list.

CC: stable@vger.kernel.org
Reported-by: NVegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

A failed call to dqget() returns an ERR_PTR() and not null. Fix
the check in ext4_ioctl_setproject() to handle this correctly.

Fixes: 9b7365fc ("ext4: add FS_IOC_FSSETXATTR/FS_IOC_FSGETXATTR interface support")
Cc: stable@vger.kernel.org # v4.5
Signed-off-by: NSeth Forshee <seth.forshee@canonical.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>

Instead of just printing warning messages, if the orphan list is
corrupted, declare the file system is corrupted.  If there are any
reserved inodes in the orphaned inode list, declare the file system
corrupted and stop right away to avoid doing more potential damage to
the file system.

Cc: stable@vger.kernel.org
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

If the orphaned inode list contains inode #5, ext4_iget() returns a
bad inode (since the bootloader inode should never be referenced
directly).  Because of the bad inode, we end up processing the inode
repeatedly and this hangs the machine.

This can be reproduced via:

   mke2fs -t ext4 /tmp/foo.img 100
   debugfs -w -R "ssv last_orphan 5" /tmp/foo.img
   mount -o loop /tmp/foo.img /mnt

(But don't do this if you are using an unpatched kernel if you care
about the system staying functional.  :-)

This bug was found by the port of American Fuzzy Lop into the kernel
to find file system problems[1].  (Since it *only* happens if inode #5
shows up on the orphan list --- 3, 7, 8, etc. won't do it, it's not
surprising that AFL needed two hours before it found it.)

[1] http://events.linuxfoundation.org/sites/events/files/slides/AFL%20filesystem%20fuzzing%2C%20Vault%202016_0.pdf

Cc: stable@vger.kernel.org
Reported by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Messages passed to ext4_warning() or ext4_error() don't need trailing
newlines, because these function add the newlines themselves.
Signed-off-by: NJakub Wilk <jwilk@jwilk.net>

In ext4, there is a race condition between changing inode journal mode
and ext4_writepages(). While ext4_writepages() is executed on a
non-journalled mode inode, the inode's journal mode could be enabled
by ioctl() and then, some pages dirtied after switching the journal
mode will be still exposed to ext4_writepages() in non-journaled mode.
To resolve this problem, we use fs-wide per-cpu rw semaphore by Jan
Kara's suggestion because we don't want to waste ext4_inode_info's
space for this extra rare case.
Signed-off-by: NDaeho Jeong <daeho.jeong@samsung.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>

We already allocate delalloc blocks before changing the inode mode into
"per-file data journal" mode to prevent delalloc blocks from remaining
not allocated, but another issue concerned with "BH_Unwritten" status
still exists. For example, by fallocate(), several buffers' status
change into "BH_Unwritten", but these buffers cannot be processed by
ext4_alloc_da_blocks(). So, they still remain in unwritten status after
per-file data journaling is enabled and they cannot be changed into
written status any more and, if they are journaled and eventually
checkpointed, these unwritten buffer will cause a kernel panic by the
below BUG_ON() function of submit_bh_wbc() when they are submitted
during checkpointing.

static int submit_bh_wbc(int rw, struct buffer_head *bh,...
{
        ...
        BUG_ON(buffer_unwritten(bh));

Moreover, when "dioread_nolock" option is enabled, the status of a
buffer is changed into "BH_Unwritten" after write_begin() completes and
the "BH_Unwritten" status will be cleared after I/O is done. Therefore,
if a buffer's status is changed into unwrutten but the buffer's I/O is
not submitted and completed, it can cause the same problem after
enabling per-file data journaling. You can easily generate this bug by
executing the following command.

./kvm-xfstests -C 10000 -m nodelalloc,dioread_nolock generic/269

To resolve these problems and define a boundary between the previous
mode and per-file data journaling mode, we need to flush and wait all
the I/O of buffers of a file before enabling per-file data journaling
of the file.
Signed-off-by: NDaeho Jeong <daeho.jeong@samsung.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>

The function jbd2_journal_extend() takes as its argument the number of
new credits to be added to the handle.  We weren't taking into account
the currently unused handle credits; worse, we would try to extend the
handle by N credits when it had N credits available.

In the case where jbd2_journal_extend() fails because the transaction
is too large, when jbd2_journal_restart() gets called, the N credits
owned by the handle gets returned to the transaction, and the
transaction commit is asynchronously requested, and then
start_this_handle() will be able to successfully attach the handle to
the current transaction since the required credits are now available.

This is mostly harmless, but since ext4_ext_truncate_extend_restart()
returns EAGAIN, the truncate machinery will once again try to call
ext4_ext_truncate_extend_restart(), which will do the above sequence
over and over again until the transaction has committed.

This was found while I was debugging a lockup in caused by running
xfstests generic/074 in the data=journal case.  I'm still not sure why
we ended up looping forever, which suggests there may still be another
bug hiding in the transaction accounting machinery, but this commit
prevents us from looping in the first place.
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently we ask jbd2 to write all dirty allocated buffers before
committing a transaction when doing writeback of delay allocated blocks.
However this is unnecessary since we move all pages to writeback state
before dropping a transaction handle and then submit all the necessary
IO. We still need the transaction commit to wait for all the outstanding
writeback before flushing disk caches during transaction commit to avoid
data exposure issues though. Use the new jbd2 capability and ask it to
only wait for outstanding writeback during transaction commit when
writing back data in ext4_writepages().
Tested-by: N"HUANG Weller (CM/ESW12-CN)" <Weller.Huang@cn.bosch.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently when filesystem needs to make sure data is on permanent
storage before committing a transaction it adds inode to transaction's
inode list. During transaction commit, jbd2 writes back all dirty
buffers that have allocated underlying blocks and waits for the IO to
finish. However when doing writeback for delayed allocated data, we
allocate blocks and immediately submit the data. Thus asking jbd2 to
write dirty pages just unnecessarily adds more work to jbd2 possibly
writing back other redirtied blocks.

Add support to jbd2 to allow filesystem to ask jbd2 to only wait for
outstanding data writes before committing a transaction and thus avoid
unnecessary writes.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

This flag is just duplicating what ext4_should_order_data() tells you
and is used in a single place. Furthermore it doesn't reflect changes to
inode data journalling flag so it may be possibly misleading. Just
remove it.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Huang has reported that in his powerfail testing he is seeing stale
block contents in some of recently allocated blocks although he mounts
ext4 in data=ordered mode. After some investigation I have found out
that indeed when delayed allocation is used, we don't add inode to
transaction's list of inodes needing flushing before commit. Originally
we were doing that but commit f3b59291 removed the logic with a
flawed argument that it is not needed.

The problem is that although for delayed allocated blocks we write their
contents immediately after allocating them, there is no guarantee that
the IO scheduler or device doesn't reorder things and thus transaction
allocating blocks and attaching them to inode can reach stable storage
before actual block contents. Actually whenever we attach freshly
allocated blocks to inode using a written extent, we should add inode to
transaction's ordered inode list to make sure we properly wait for block
contents to be written before committing the transaction. So that is
what we do in this patch. This also handles other cases where stale data
exposure was possible - like filling hole via mmap in
data=ordered,nodelalloc mode.

The only exception to the above rule are extending direct IO writes where
blkdev_direct_IO() waits for IO to complete before increasing i_size and
thus stale data exposure is not possible. For now we don't complicate
the code with optimizing this special case since the overhead is pretty
low. In case this is observed to be a performance problem we can always
handle it using a special flag to ext4_map_blocks().

CC: stable@vger.kernel.org
Fixes: f3b59291Reported-by: N"HUANG Weller (CM/ESW12-CN)" <Weller.Huang@cn.bosch.com>
Tested-by: N"HUANG Weller (CM/ESW12-CN)" <Weller.Huang@cn.bosch.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

If a directory has a large number of empty blocks, iterating over all
of them can take a long time, leading to scheduler warnings and users
getting irritated when they can't kill a process in the middle of one
of these long-running readdir operations.  Fix this by adding checks to
ext4_readdir() and ext4_htree_fill_tree().

This was reverted earlier due to a typo in the original commit where I
experimented with using signal_pending() instead of
fatal_signal_pending().  The test was in the wrong place if we were
going to return signal_pending() since we would end up returning
duplicant entries.  See 9f2394c9 for a more detailed explanation.

Added fix as suggested by Linus to check for signal_pending() in
in the filldir() functions.
Reported-by: NBenjamin LaHaise <bcrl@kvack.org>
Google-Bug-Id: 27880676
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Pull device mapper fix from Mike Snitzer:
 "Fix for earlier 4.6-rc4 stable@ commit that introduced improper use of
  write lock in cmd_read_lock() -- due to cut-n-paste gone awry (and
  sparse didn't catch it)"

* tag 'dm-4.6-fix-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm cache metadata: fix cmd_read_lock() acquiring write lock