linux-stable.git/include/linux/shmem_fs.h, branch v6.0.2

mm/shmem: fix chattr fsflags support in tmpfs

2022-08-20T22:17:45+00:00

ext[234] have always allowed unimplemented chattr flags to be set, but
other filesystems have tended to be stricter.  Follow the stricter
approach for tmpfs: I don't want to have to explain why csu attributes
don't actually work, and we won't need to update the chattr(1) manpage;
and it's never wrong to start off strict, relaxing later if persuaded. 
Allow only a (append only) i (immutable) A (no atime) and d (no dump).

Although lsattr showed 'A' inherited, the NOATIME behavior was not being
inherited: because nothing sync'ed FS_NOATIME_FL to S_NOATIME.  Add
shmem_set_inode_flags() to sync the flags, using inode_set_flags() to
avoid that instant of lost immutablility during fileattr_set().

But that change switched generic/079 from passing to failing: because
FS_IMMUTABLE_FL and FS_APPEND_FL had been unconventionally included in the
INHERITED fsflags: remove them and generic/079 is back to passing.

Link: https://lkml.kernel.org/r/2961dcb0-ddf3-b9f0-3268-12a4ff996856@google.com
Fixes: e408e695f5f1 ("mm/shmem: support FS_IOC_[SG]ETFLAGS in tmpfs")
Signed-off-by: Hugh Dickins 
Cc: "Theodore Ts'o" 
Cc: Radoslaw Burny 
Cc: "Darrick J. Wong" 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

mm/shmem: support FS_IOC_[SG]ETFLAGS in tmpfs

2022-07-30T01:07:15+00:00

This allows userspace to set flags like FS_APPEND_FL, FS_IMMUTABLE_FL,
FS_NODUMP_FL, etc., like all other standard Linux file systems.

[akpm@linux-foundation.org: fix CONFIG_TMPFS_XATTR=n warnings]
Link: https://lkml.kernel.org/r/20220715015912.2560575-1-tytso@mit.edu
Signed-off-by: Theodore Ts'o 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton

mm/shmem: take care of UFFDIO_COPY_MODE_WP

2022-05-13T14:20:10+00:00

Pass wp_copy into shmem_mfill_atomic_pte() through the stack, then apply
the UFFD_WP bit properly when the UFFDIO_COPY on shmem is with
UFFDIO_COPY_MODE_WP.  wp_copy lands mfill_atomic_install_pte() finally.

Note: we must do pte_wrprotect() if !writable in
mfill_atomic_install_pte(), as mk_pte() could return a writable pte (e.g.,
when VM_SHARED on a shmem file).

Link: https://lkml.kernel.org/r/20220405014841.14185-1-peterx@redhat.com
Signed-off-by: Peter Xu 
Cc: Alistair Popple 
Cc: Andrea Arcangeli 
Cc: Axel Rasmussen 
Cc: David Hildenbrand 
Cc: Hugh Dickins 
Cc: Jerome Glisse 
Cc: "Kirill A . Shutemov" 
Cc: Matthew Wilcox 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Nadav Amit 
Signed-off-by: Andrew Morton

mm: shmem: make shmem_init return void

2022-04-29T06:15:58+00:00

The return value of shmem_init is never used.  So we can make it return
void now.

[akpm@linux-foundation.org: remove `return;' from void-returning function, per Muchun Song]
Link: https://lkml.kernel.org/r/20220328112707.22217-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Cc: Muchun Song 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton

tmpfs: support for file creation time

2022-03-22T22:57:01+00:00

Various filesystems (including ext4) now support file creation time.
This adds such support for tmpfs-based filesystems.

Note that using shmem_getattr() on other file types than regular
requires that shmem_is_huge() check type, to stop incorrect
HPAGE_PMD_SIZE blksize.

[hughd@google.com: three tweaks to creation time patch]
  Link: https://lkml.kernel.org/r/b954973a-b8d1-cab8-63bd-6ea8063de3@google.com

Link: https://lkml.kernel.org/r/20220314211150.GA123458@xavier-xps
Link: https://lkml.kernel.org/r/b954973a-b8d1-cab8-63bd-6ea8063de3@google.com
Link: https://lkml.kernel.org/r/20220211213628.GA1919658@xavier-xps
Signed-off-by: Xavier Roche 
Signed-off-by: Hugh Dickins 
Tested-by: Jean Delvare 
Tested-by: Sylvain Bellone 
Reported-by: Xavier Grand 
Reviewed-by: Jean Delvare 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: simplify try_to_unuse

2022-01-22T06:33:38+00:00

Remove the unused frontswap and pages_to_unuse arguments, and mark the
function static now that the caller in frontswap is gone.

[akpm@linux-foundation.org: fix shmem_unuse() stub, per Matthew]

Link: https://lkml.kernel.org/r/20211224062246.1258487-9-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Cc: Naresh Kamboju 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

huge tmpfs: shmem_is_huge(vma, inode, index)

2021-09-03T16:58:12+00:00

Extend shmem_huge_enabled(vma) to shmem_is_huge(vma, inode, index), so
that a consistent set of checks can be applied, even when the inode is
accessed through read/write syscalls (with NULL vma) instead of mmaps (the
index argument is seldom of interest, but required by mount option
"huge=within_size").  Clean up and rearrange the checks a little.

This then replaces the checks which shmem_fault() and shmem_getpage_gfp()
were making, and eliminates the SGP_HUGE and SGP_NOHUGE modes.

Replace a couple of 0s by explicit SHMEM_HUGE_NEVERs; and replace the
obscure !shmem_mapping() symlink check by explicit S_ISLNK() - nothing
else needs that symlink check, so leave it there in shmem_getpage_gfp().

Link: https://lkml.kernel.org/r/23a77889-2ddc-b030-75cd-44ca27fd4d1@google.com
Signed-off-by: Hugh Dickins 
Reviewed-by: Yang Shi 
Cc: "Kirill A. Shutemov" 
Cc: Matthew Wilcox 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Kravetz 
Cc: Rik van Riel 
Cc: Shakeel Butt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

huge tmpfs: SGP_NOALLOC to stop collapse_file() on race

2021-09-03T16:58:12+00:00

khugepaged's collapse_file() currently uses SGP_NOHUGE to tell
shmem_getpage() not to try allocating a huge page, in the very unlikely
event that a racing hole-punch removes the swapped or fallocated page as
soon as i_pages lock is dropped.

We want to consolidate shmem's huge decisions, removing SGP_HUGE and
SGP_NOHUGE; but cannot quite persuade ourselves that it's okay to regress
the protection in this case - Yang Shi points out that the huge page would
remain indefinitely, charged to root instead of the intended memcg.

collapse_file() should not even allocate a small page in this case: why
proceed if someone is punching a hole?  SGP_READ is almost the right flag
here, except that it optimizes away from a fallocated page, with NULL to
tell caller to fill with zeroes (like a hole); whereas collapse_file()'s
sequence relies on using a cache page.  Add SGP_NOALLOC just for this.

There are too many consecutive "if (page"s there in shmem_getpage_gfp():
group it better; and fix the outdated "bring it back from swap" comment.

Link: https://lkml.kernel.org/r/1355343b-acf-4653-ef79-6aee40214ac5@google.com
Signed-off-by: Hugh Dickins 
Reviewed-by: Yang Shi 
Cc: "Kirill A. Shutemov" 
Cc: Matthew Wilcox 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Kravetz 
Cc: Rik van Riel 
Cc: Shakeel Butt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

huge tmpfs: fix split_huge_page() after FALLOC_FL_KEEP_SIZE

2021-09-03T16:58:11+00:00

A successful shmem_fallocate() guarantees that the extent has been
reserved, even beyond i_size when the FALLOC_FL_KEEP_SIZE flag was used.
But that guarantee is broken by shmem_unused_huge_shrink()'s attempts to
split huge pages and free their excess beyond i_size; and by other uses of
split_huge_page() near i_size.

It's sad to add a shmem inode field just for this, but I did not find a
better way to keep the guarantee.  A flag to say KEEP_SIZE has been used
would be cheaper, but I'm averse to unclearable flags.  The fallocend
field is not perfect either (many disjoint ranges might be fallocated),
but good enough; and gains another use later on.

Link: https://lkml.kernel.org/r/ca9a146-3a59-6cd3-7f28-e9a044bb1052@google.com
Fixes: 779750d20b93 ("shmem: split huge pages beyond i_size under memory pressure")
Signed-off-by: Hugh Dickins 
Reviewed-by: Yang Shi 
Cc: "Kirill A. Shutemov" 
Cc: Matthew Wilcox 
Cc: Miaohe Lin 
Cc: Michal Hocko 
Cc: Mike Kravetz 
Cc: Rik van Riel 
Cc: Shakeel Butt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

shmem: use raw_spinlock_t for ->stat_lock

2021-09-03T16:58:11+00:00

Each CPU has SHMEM_INO_BATCH inodes available in `->ino_batch' which is
per-CPU.  Access here is serialized by disabling preemption.  If the pool
is empty, it gets reloaded from `->next_ino'.  Access here is serialized
by ->stat_lock which is a spinlock_t and can not be acquired with disabled
preemption.

One way around it would make per-CPU ino_batch struct containing the inode
number a local_lock_t.

Another solution is to promote ->stat_lock to a raw_spinlock_t.  The
critical sections are short.  The mpol_put() must be moved outside of the
critical section to avoid invoking the destructor with disabled
preemption.

Link: https://lkml.kernel.org/r/20210806142916.jdwkb5bx62q5fwfo@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds