linux.git/fs/nilfs2/segment.c, branch v5.8

nilfs2: fix null pointer dereference at nilfs_segctor_do_construct()

2020-06-11T02:14:17+00:00

After commit c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if
mapping has no dirty pages"), the following null pointer dereference has
been reported on nilfs2:

  BUG: kernel NULL pointer dereference, address: 00000000000000a8
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP PTI
  ...
  RIP: 0010:percpu_counter_add_batch+0xa/0x60
  ...
  Call Trace:
    __test_set_page_writeback+0x2d3/0x330
    nilfs_segctor_do_construct+0x10d3/0x2110 [nilfs2]
    nilfs_segctor_construct+0x168/0x260 [nilfs2]
    nilfs_segctor_thread+0x127/0x3b0 [nilfs2]
    kthread+0xf8/0x130
    ...

This crash turned out to be caused by set_page_writeback() call for
segment summary buffers at nilfs_segctor_prepare_write().

set_page_writeback() can call inc_wb_stat(inode_to_wb(inode),
WB_WRITEBACK) where inode_to_wb(inode) is NULL if the inode of
underlying block device does not have an associated wb.

This fixes the issue by calling inode_attach_wb() in advance to ensure
to associate the bdev inode with its wb.

Fixes: c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if mapping has no dirty pages")
Reported-by: Walton Hoops 
Reported-by: Tomas Hlavaty 
Reported-by: ARAI Shun-ichi 
Reported-by: Hideki EIRAKU 
Signed-off-by: Ryusuke Konishi 
Signed-off-by: Andrew Morton 
Tested-by: Ryusuke Konishi 
Cc: 	[5.4+]
Link: http://lkml.kernel.org/r/20200608.011819.1399059588922299158.konishi.ryusuke@gmail.com
Signed-off-by: Linus Torvalds

nilfs2: convert to SPDX license tags

2018-09-04T23:45:02+00:00

Remove the verbose license text from NILFS2 files and replace them with
SPDX tags.  This does not change the license of any of the code.

Link: http://lkml.kernel.org/r/1535624528-5982-1-git-send-email-konishi.ryusuke@lab.ntt.co.jp
Signed-off-by: Ryusuke Konishi 
Reviewed-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nilfs2: use time64_t internally

2018-02-07T02:32:45+00:00

The superblock and segment timestamps are used only internally in nilfs2
and can be read out using sysfs.

Since we are using the old 'get_seconds()' interface and store the data
as timestamps, the behavior differs slightly between 64-bit and 32-bit
kernels, the latter will show incorrect timestamps after 2038 in sysfs,
and presumably fail completely in 2106 as comparisons go wrong.

This changes nilfs2 to use time64_t with ktime_get_real_seconds() to
handle timestamps, making the behavior consistent and correct on both
32-bit and 64-bit machines.

The on-disk format already uses 64-bit timestamps, so nothing changes
there.

Link: http://lkml.kernel.org/r/20180122211050.1286441-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann 
Acked-by: Ryusuke Konishi 
Cc: Jens Axboe 
Cc: Ingo Molnar 
Cc: Jan Kara 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Rename superblock flags (MS_xyz -> SB_xyz)

2017-11-27T21:05:09+00:00

This is a pure automated search-and-replace of the internal kernel
superblock flags.

The s_flags are now called SB_*, with the names and the values for the
moment mirroring the MS_* flags that they're equivalent to.

Note how the MS_xyz flags are the ones passed to the mount system call,
while the SB_xyz flags are what we then use in sb->s_flags.

The script to do this was:

    # places to look in; re security/*: it generally should *not* be
    # touched (that stuff parses mount(2) arguments directly), but
    # there are two places where we really deal with superblock flags.
    FILES="drivers/mtd drivers/staging/lustre fs ipc mm \
            include/linux/fs.h include/uapi/linux/bfs_fs.h \
            security/apparmor/apparmorfs.c security/apparmor/include/lib.h"
    # the list of MS_... constants
    SYMS="RDONLY NOSUID NODEV NOEXEC SYNCHRONOUS REMOUNT MANDLOCK \
          DIRSYNC NOATIME NODIRATIME BIND MOVE REC VERBOSE SILENT \
          POSIXACL UNBINDABLE PRIVATE SLAVE SHARED RELATIME KERNMOUNT \
          I_VERSION STRICTATIME LAZYTIME SUBMOUNT NOREMOTELOCK NOSEC BORN \
          ACTIVE NOUSER"

    SED_PROG=
    for i in $SYMS; do SED_PROG="$SED_PROG -e s/MS_$i/SB_$i/g"; done

    # we want files that contain at least one of MS_...,
    # with fs/namespace.c and fs/pnode.c excluded.
    L=$(for i in $SYMS; do git grep -w -l MS_$i $FILES; done| sort|uniq|grep -v '^fs/namespace.c'|grep -v '^fs/pnode.c')

    for f in $L; do sed -i $f $SED_PROG; done

Requested-by: Al Viro 
Signed-off-by: Linus Torvalds

nilfs2: fix race condition that causes file system corruption

2017-11-18T00:10:03+00:00

There is a race condition between nilfs_dirty_inode() and
nilfs_set_file_dirty().

When a file is opened, nilfs_dirty_inode() is called to update the
access timestamp in the inode.  It calls __nilfs_mark_inode_dirty() in a
separate transaction.  __nilfs_mark_inode_dirty() caches the ifile
buffer_head in the i_bh field of the inode info structure and marks it
as dirty.

After some data was written to the file in another transaction, the
function nilfs_set_file_dirty() is called, which adds the inode to the
ns_dirty_files list.

Then the segment construction calls nilfs_segctor_collect_dirty_files(),
which goes through the ns_dirty_files list and checks the i_bh field.
If there is a cached buffer_head in i_bh it is not marked as dirty
again.

Since nilfs_dirty_inode() and nilfs_set_file_dirty() use separate
transactions, it is possible that a segment construction that writes out
the ifile occurs in-between the two.  If this happens the inode is not
on the ns_dirty_files list, but its ifile block is still marked as dirty
and written out.

In the next segment construction, the data for the file is written out
and nilfs_bmap_propagate() updates the b-tree.  Eventually the bmap root
is written into the i_bh block, which is not dirty, because it was
written out in another segment construction.

As a result the bmap update can be lost, which leads to file system
corruption.  Either the virtual block address points to an unallocated
DAT block, or the DAT entry will be reused for something different.

The error can remain undetected for a long time.  A typical error
message would be one of the "bad btree" errors or a warning that a DAT
entry could not be found.

This bug can be reproduced reliably by a simple benchmark that creates
and overwrites millions of 4k files.

Link: http://lkml.kernel.org/r/1509367935-3086-2-git-send-email-konishi.ryusuke@lab.ntt.co.jp
Signed-off-by: Andreas Rohner 
Signed-off-by: Ryusuke Konishi 
Tested-by: Andreas Rohner 
Tested-by: Ryusuke Konishi 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs/nilfs2: convert timers to use timer_setup()

2017-11-18T00:10:03+00:00

In preparation for unconditionally passing the struct timer_list pointer
to all timer callbacks, switch to using the new timer_setup() and
from_timer() to pass the timer pointer explicitly.  This requires adding
a pointer to hold the timer's target task, as the lifetime of sc_task
doesn't appear to match the timer's task.

Link: http://lkml.kernel.org/r/20171016235900.GA102729@beast
Signed-off-by: Kees Cook 
Acked-by: Ryusuke Konishi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, pagevec: remove cold parameter for pagevecs

2017-11-16T02:21:06+00:00

Every pagevec_init user claims the pages being released are hot even in
cases where it is unlikely the pages are hot.  As no one cares about the
hotness of pages being released to the allocator, just ditch the
parameter.

No performance impact is expected as the overhead is marginal.  The
parameter is removed simply because it is a bit stupid to have a useless
parameter copied everywhere.

Link: http://lkml.kernel.org/r/20171018075952.10627-6-mgorman@techsingularity.net
Signed-off-by: Mel Gorman 
Acked-by: Vlastimil Babka 
Cc: Andi Kleen 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Jan Kara 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: remove nr_pages argument from pagevec_lookup_{,range}_tag()

2017-11-16T02:21:04+00:00

All users of pagevec_lookup() and pagevec_lookup_range() now pass
PAGEVEC_SIZE as a desired number of pages.  Just drop the argument.

Link: http://lkml.kernel.org/r/20171009151359.31984-15-jack@suse.cz
Signed-off-by: Jan Kara 
Reviewed-by: Daniel Jordan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nilfs2: use pagevec_lookup_range_tag()

2017-11-16T02:21:04+00:00

We want only pages from given range in nilfs_lookup_dirty_data_buffers().
Use pagevec_lookup_range_tag() instead of pagevec_lookup_tag() and
remove unnecessary code.

Link: http://lkml.kernel.org/r/20171009151359.31984-10-jack@suse.cz
Signed-off-by: Jan Kara 
Reviewed-by: Daniel Jordan 
Acked-by: Ryusuke Konishi 
Cc: Ryusuke Konishi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming

2017-06-20T10:19:14+00:00

So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.

Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.

To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:

	struct wait_queue_head::task_list	=> ::head
	struct wait_queue_entry::task_list	=> ::entry

For example, this code:

	rqw->wait.task_list.next != &wait->task_list

... is was pretty unclear (to me) what it's doing, while now it's written this way:

	rqw->wait.head.next != &wait->entry

... which makes it pretty clear that we are iterating a list until we see the head.

Other examples are:

	list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
	list_for_each_entry(wq, &fence->wait.task_list, task_list) {

... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:

	list_for_each_entry_safe(pos, next, &x->head, entry) {
	list_for_each_entry(wq, &fence->wait.head, entry) {

Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar