linux-toradex.git/mm/shmem.c, branch v4.10

shmem: fix sleeping from atomic context

2017-02-03T22:13:19+00:00

Syzkaller fuzzer managed to trigger this:

    BUG: sleeping function called from invalid context at mm/shmem.c:852
    in_atomic(): 1, irqs_disabled(): 0, pid: 529, name: khugepaged
    3 locks held by khugepaged/529:
     #0:  (shrinker_rwsem){++++..}, at: [] shrink_slab.part.59+0x121/0xd30 mm/vmscan.c:451
     #1:  (&type->s_umount_key#29){++++..}, at: [] trylock_super+0x20/0x100 fs/super.c:392
     #2:  (&(&sbinfo->shrinklist_lock)->rlock){+.+.-.}, at: [] spin_lock include/linux/spinlock.h:302 [inline]
     #2:  (&(&sbinfo->shrinklist_lock)->rlock){+.+.-.}, at: [] shmem_unused_huge_shrink+0x28e/0x1490 mm/shmem.c:427
    CPU: 2 PID: 529 Comm: khugepaged Not tainted 4.10.0-rc5+ #201
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    Call Trace:
       shmem_undo_range+0xb20/0x2710 mm/shmem.c:852
       shmem_truncate_range+0x27/0xa0 mm/shmem.c:939
       shmem_evict_inode+0x35f/0xca0 mm/shmem.c:1030
       evict+0x46e/0x980 fs/inode.c:553
       iput_final fs/inode.c:1515 [inline]
       iput+0x589/0xb20 fs/inode.c:1542
       shmem_unused_huge_shrink+0xbad/0x1490 mm/shmem.c:446
       shmem_unused_huge_scan+0x10c/0x170 mm/shmem.c:512
       super_cache_scan+0x376/0x450 fs/super.c:106
       do_shrink_slab mm/vmscan.c:378 [inline]
       shrink_slab.part.59+0x543/0xd30 mm/vmscan.c:481
       shrink_slab mm/vmscan.c:2592 [inline]
       shrink_node+0x2c7/0x870 mm/vmscan.c:2592
       shrink_zones mm/vmscan.c:2734 [inline]
       do_try_to_free_pages+0x369/0xc80 mm/vmscan.c:2776
       try_to_free_pages+0x3c6/0x900 mm/vmscan.c:2982
       __perform_reclaim mm/page_alloc.c:3301 [inline]
       __alloc_pages_direct_reclaim mm/page_alloc.c:3322 [inline]
       __alloc_pages_slowpath+0xa24/0x1c30 mm/page_alloc.c:3683
       __alloc_pages_nodemask+0x544/0xae0 mm/page_alloc.c:3848
       __alloc_pages include/linux/gfp.h:426 [inline]
       __alloc_pages_node include/linux/gfp.h:439 [inline]
       khugepaged_alloc_page+0xc2/0x1b0 mm/khugepaged.c:750
       collapse_huge_page+0x182/0x1fe0 mm/khugepaged.c:955
       khugepaged_scan_pmd+0xfdf/0x12a0 mm/khugepaged.c:1208
       khugepaged_scan_mm_slot mm/khugepaged.c:1727 [inline]
       khugepaged_do_scan mm/khugepaged.c:1808 [inline]
       khugepaged+0xe9b/0x1590 mm/khugepaged.c:1853
       kthread+0x326/0x3f0 kernel/kthread.c:227
       ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430

The iput() from atomic context was a bad idea: if after igrab() somebody
else calls iput() and we left with the last inode reference, our iput()
would lead to inode eviction and therefore sleeping.

This patch should fix the situation.

Link: http://lkml.kernel.org/r/20170131093141.GA15899@node.shutemov.name
Signed-off-by: Kirill A. Shutemov 
Reported-by: Dmitry Vyukov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Replace with globally

2016-12-24T19:46:01+00:00

This was entirely automated, using the script by Al:

  PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*'
  sed -i -e "s!$PATT!#include !" \
        $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)

to do the replacement at the end of the merge window.

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

Merge uncontroversial parts of branch 'readlink' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

2016-12-18T03:16:12+00:00

Pull partial readlink cleanups from Miklos Szeredi.

This is the uncontroversial part of the readlink cleanup patch-set that
simplifies the default readlink handling.

Miklos and Al are still discussing the rest of the series.

* git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  vfs: make generic_readlink() static
  vfs: remove ".readlink = generic_readlink" assignments
  vfs: default to generic_readlink()
  vfs: replace calling i_op->readlink with vfs_readlink()
  proc/self: use generic_readlink
  ecryptfs: use vfs_get_link()
  bad_inode: add missing i_op initializers

radix-tree: delete radix_tree_locate_item()

2016-12-15T00:04:10+00:00

This rather complicated function can be better implemented as an
iterator.  It has only one caller, so move the functionality to the only
place that needs it.  Update the test suite to follow the same pattern.

Link: http://lkml.kernel.org/r/1480369871-5271-56-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox 
Acked-by: Konstantin Khlebnikov 
Tested-by: Kirill A. Shutemov 
Cc: Ross Zwisler 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

radix-tree: improve multiorder iterators

2016-12-15T00:04:10+00:00

This fixes several interlinked problems with the iterators in the
presence of multiorder entries.

1. radix_tree_iter_next() would only advance by one slot, which would
   result in the iterators returning the same entry more than once if
   there were sibling entries.

2. radix_tree_next_slot() could return an internal pointer instead of
   a user pointer if a tagged multiorder entry was immediately followed by
   an entry of lower order.

3. radix_tree_next_slot() expanded to a lot more code than it used to
   when multiorder support was compiled in.  And I wasn't comfortable with
   entry_to_node() being in a header file.

Fixing radix_tree_iter_next() for the presence of sibling entries
necessarily involves examining the contents of the radix tree, so we now
need to pass 'slot' to radix_tree_iter_next(), and we need to change the
calling convention so it is called *before* dropping the lock which
protects the tree.  Also rename it to radix_tree_iter_resume(), as some
people thought it was necessary to call radix_tree_iter_next() each time
around the loop.

radix_tree_next_slot() becomes closer to how it looked before multiorder
support was introduced.  It only checks to see if the next entry in the
chunk is a sibling entry or a pointer to a node; this should be rare
enough that handling this case out of line is not a performance impact
(and such impact is amortised by the fact that the entry we just
processed was a multiorder entry).  Also, radix_tree_next_slot() used to
force a new chunk lookup for untagged entries, which is more expensive
than the out of line sibling entry skipping.

Link: http://lkml.kernel.org/r/1480369871-5271-55-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox 
Tested-by: Kirill A. Shutemov 
Cc: Konstantin Khlebnikov 
Cc: Ross Zwisler 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

lib: radix-tree: update callback for changing leaf nodes

2016-12-13T02:55:08+00:00

Support handing __radix_tree_replace() a callback that gets invoked for
all leaf nodes that change or get freed as a result of the slot
replacement, to assist users tracking nodes with node->private_list.

This prepares for putting page cache shadow entries into the radix tree
root again and drastically simplifying the shadow tracking.

Link: http://lkml.kernel.org/r/20161117193134.GD23430@cmpxchg.org
Signed-off-by: Johannes Weiner 
Suggested-by: Jan Kara 
Reviewed-by: Jan Kara 
Cc: Kirill A. Shutemov 
Cc: Hugh Dickins 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

lib: radix-tree: native accounting of exceptional entries

2016-12-13T02:55:08+00:00

The way the page cache is sneaking shadow entries of evicted pages into
the radix tree past the node entry accounting and tracking them manually
in the upper bits of node->count is fraught with problems.

These shadow entries are marked in the tree as exceptional entries,
which are a native concept to the radix tree.  Maintain an explicit
counter of exceptional entries in the radix tree node.  Subsequent
patches will switch shadow entry tracking over to that counter.

DAX and shmem are the other users of exceptional entries.  Since slot
replacements that change the entry type from regular to exceptional must
now be accounted, introduce a __radix_tree_replace() function that does
replacement and accounting, and switch DAX and shmem over.

The increase in radix tree node size is temporary.  A followup patch
switches the shadow tracking to this new scheme and we'll no longer need
the upper bits in node->count and shrink that back to one byte.

Link: http://lkml.kernel.org/r/20161117192945.GA23430@cmpxchg.org
Signed-off-by: Johannes Weiner 
Reviewed-by: Jan Kara 
Cc: Kirill A. Shutemov 
Cc: Hugh Dickins 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

shmem: fix compilation warnings on unused functions

2016-12-13T02:55:08+00:00

Compiling shmem.c with SHMEM and TRANSAPRENT_HUGE_PAGECACHE enabled
raises warnings on two unused functions when CONFIG_TMPFS and
CONFIG_SYSFS are both disabled:

  mm/shmem.c:390:20: warning: `shmem_format_huge' defined but not used [-Wunused-function]
   static const char *shmem_format_huge(int huge)
                      ^~~~~~~~~~~~~~~~~
  mm/shmem.c:373:12: warning: `shmem_parse_huge' defined but not used [-Wunused-function]
   static int shmem_parse_huge(const char *str)
               ^~~~~~~~~~~~~~~~

A conditional compilation on tmpfs or sysfs removes the warnings.

Link: http://lkml.kernel.org/r/20161118055749.11313-1-jeremy.lefaure@lse.epita.fr
Signed-off-by: Jérémy Lefaure 
Acked-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

shmem: avoid maybe-uninitialized warning

2016-12-13T02:55:07+00:00

After enabling -Wmaybe-uninitialized warnings, we get a false-postive
warning for shmem:

  mm/shmem.c: In function `shmem_getpage_gfp':
  include/linux/spinlock.h:332:21: error: `info' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This can be easily avoided, since the correct 'info' pointer is known at
the time we first enter the function, so we can simply move the
initialization up.  Moving it before the first label avoids the warning
and lets us remove two later initializations.

Note that the function is so hard to read that it not only confuses the
compiler, but also most readers and without this patch it could\ easily
break if one of the 'goto's changed.

Link: https://www.spinics.net/lists/kernel/msg2368133.html
Link: http://lkml.kernel.org/r/20161024205725.786455-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann 
Acked-by: Michal Hocko 
Acked-by: Kirill A. Shutemov 
Acked-by: Vlastimil Babka 
Cc: Hugh Dickins 
Cc: Andreas Gruenbacher 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vfs: remove ".readlink = generic_readlink" assignments

2016-12-09T15:45:04+00:00

If .readlink == NULL implies generic_readlink().

Generated by:

to_del="\.readlink.*=.*generic_readlink"
for i in `git grep -l $to_del`; do sed -i "/$to_del"/d $i; done

Signed-off-by: Miklos Szeredi