Let me count the ways in which I'd screwed up:
* when emitting a page, handling of gaps in coredump should happen
before fetching the current file position.
* fix for a problem that occurs on rather uncommon setups (and hadn't
been observed in the wild) had been sent very late in the cycle.
* ... with badly insufficient testing, introducing an easily
reproducible breakage. Without giving it time to soak in -next.
Fucked-up-by: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: "J. R. Okajima" <hooanon05g@gmail.com>
Tested-by: "J. R. Okajima" <hooanon05g@gmail.com>
Fixes: 06bbaa6dc5 "[coredump] don't use __kernel_write() on kmap_local_page()"
Cc: stable@kernel.org # v6.0-only
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull execve updates from Kees Cook:
"This removes a.out support globally; it has been disabled for a while
now.
- Remove a.out implementation globally (Eric W. Biederman)
- Remove unused linux_binprm::taso member (Lukas Bulwahn)"
* tag 'execve-v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
binfmt: remove taso from linux_binprm struct
a.out: Remove the a.out implementation
Mark
/proc/devices
/proc/kpagecount
/proc/kpageflags
/proc/kpagecgroup
/proc/loadavg
/proc/meminfo
/proc/softirqs
/proc/uptime
/proc/version
as permanent /proc entries, saving alloc/free and some list/spinlock ops
per use.
These files are never removed by the kernel so it is OK to mark them.
Link: https://lkml.kernel.org/r/Yyn527DzDMa+r0Yj@localhost.localdomain
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit 2e13ba54a2 ("fs, proc: introduce CONFIG_PROC_CHILDREN")
introduces the config PROC_CHILDREN to configure kernels to provide the
/proc/<pid>/task/<tid>/children file.
When one deselects PROC_FS for kernel builds without /proc/, the config
PROC_CHILDREN has no effect anymore, but is still visible in menuconfig.
Add the dependency on PROC_FS to make the PROC_CHILDREN option disappear
for kernel builds without /proc/.
Link: https://lkml.kernel.org/r/20220909122529.1941-1-lukas.bulwahn@gmail.com
Fixes: 2e13ba54a2 ("fs, proc: introduce CONFIG_PROC_CHILDREN")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Iago López Galeiras <iago@endocode.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The new hugetlb vma lock is used to address this race:
Faulting thread Unsharing thread
... ...
ptep = huge_pte_offset()
or
ptep = huge_pte_alloc()
...
i_mmap_lock_write
lock page table
ptep invalid <------------------------ huge_pmd_unshare()
Could be in a previously unlock_page_table
sharing process or worse i_mmap_unlock_write
...
The vma_lock is used as follows:
- During fault processing. The lock is acquired in read mode before
doing a page table lock and allocation (huge_pte_alloc). The lock is
held until code is finished with the page table entry (ptep).
- The lock must be held in write mode whenever huge_pmd_unshare is
called.
Lock ordering issues come into play when unmapping a page from all
vmas mapping the page. The i_mmap_rwsem must be held to search for the
vmas, and the vma lock must be held before calling unmap which will
call huge_pmd_unshare. This is done today in:
- try_to_migrate_one and try_to_unmap_ for page migration and memory
error handling. In these routines we 'try' to obtain the vma lock and
fail to unmap if unsuccessful. Calling routines already deal with the
failure of unmapping.
- hugetlb_vmdelete_list for truncation and hole punch. This routine
also tries to acquire the vma lock. If it fails, it skips the
unmapping. However, we can not have file truncation or hole punch
fail because of contention. After hugetlb_vmdelete_list, truncation
and hole punch call remove_inode_hugepages. remove_inode_hugepages
checks for mapped pages and call hugetlb_unmap_file_page to unmap them.
hugetlb_unmap_file_page is designed to drop locks and reacquire in the
correct order to guarantee unmap success.
Link: https://lkml.kernel.org/r/20220914221810.95771-9-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: James Houghton <jthoughton@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit c0d0381ade ("hugetlbfs: use i_mmap_rwsem for more pmd sharing
synchronization") added code to take i_mmap_rwsem in read mode for the
duration of fault processing. However, this has been shown to cause
performance/scaling issues. Revert the code and go back to only taking
the semaphore in huge_pmd_share during the fault path.
Keep the code that takes i_mmap_rwsem in write mode before calling
try_to_unmap as this is required if huge_pmd_unshare is called.
NOTE: Reverting this code does expose the following race condition.
Faulting thread Unsharing thread
... ...
ptep = huge_pte_offset()
or
ptep = huge_pte_alloc()
...
i_mmap_lock_write
lock page table
ptep invalid <------------------------ huge_pmd_unshare()
Could be in a previously unlock_page_table
sharing process or worse i_mmap_unlock_write
...
ptl = huge_pte_lock(ptep)
get/update pte
set_pte_at(pte, ptep)
It is unknown if the above race was ever experienced by a user. It was
discovered via code inspection when initially addressed.
In subsequent patches, a new synchronization mechanism will be added to
coordinate pmd sharing and eliminate this race.
Link: https://lkml.kernel.org/r/20220914221810.95771-3-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: James Houghton <jthoughton@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "hugetlb: Use new vma lock for huge pmd sharing
synchronization", v2.
hugetlb fault scalability regressions have recently been reported [1].
This is not the first such report, as regressions were also noted when
commit c0d0381ade ("hugetlbfs: use i_mmap_rwsem for more pmd sharing
synchronization") was added [2] in v5.7. At that time, a proposal to
address the regression was suggested [3] but went nowhere.
The regression and benefit of this patch series is not evident when
using the vm_scalability benchmark reported in [2] on a recent kernel.
Results from running,
"./usemem -n 48 --prealloc --prefault -O -U 3448054972"
48 sample Avg
next-20220913 next-20220913 next-20220913
unmodified revert i_mmap_sema locking vma sema locking, this series
-----------------------------------------------------------------------------
498150 KB/s 501934 KB/s 504793 KB/s
The recent regression report [1] notes page fault and fork latency of
shared hugetlb mappings. To measure this, I created two simple programs:
1) map a shared hugetlb area, write fault all pages, unmap area
Do this in a continuous loop to measure faults per second
2) map a shared hugetlb area, write fault a few pages, fork and exit
Do this in a continuous loop to measure forks per second
These programs were run on a 48 CPU VM with 320GB memory. The shared
mapping size was 250GB. For comparison, a single instance of the program
was run. Then, multiple instances were run in parallel to introduce
lock contention. Changing the locking scheme results in a significant
performance benefit.
test instances unmodified revert vma
--------------------------------------------------------------------------
faults per sec 1 393043 395680 389932
faults per sec 24 71405 81191 79048
forks per sec 1 2802 2747 2725
forks per sec 24 439 536 500
Combined faults 24 1621 68070 53662
Combined forks 24 358 67 142
Combined test is when running both faulting program and forking program
simultaneously.
Patches 1 and 2 of this series revert c0d0381ade and 87bf91d39b which
depends on c0d0381ade. Acquisition of i_mmap_rwsem is still required in
the fault path to establish pmd sharing, so this is moved back to
huge_pmd_share. With c0d0381ade reverted, this race is exposed:
Faulting thread Unsharing thread
... ...
ptep = huge_pte_offset()
or
ptep = huge_pte_alloc()
...
i_mmap_lock_write
lock page table
ptep invalid <------------------------ huge_pmd_unshare()
Could be in a previously unlock_page_table
sharing process or worse i_mmap_unlock_write
...
ptl = huge_pte_lock(ptep)
get/update pte
set_pte_at(pte, ptep)
Reverting 87bf91d39b exposes races in page fault/file truncation. When
the new vma lock is put to use in patch 8, this will handle the fault/file
truncation races. This is explained in patch 9 where code associated with
these races is cleaned up.
Patches 3 - 5 restructure existing code in preparation for using the new
vma lock (rw semaphore) for pmd sharing synchronization. The idea is that
this semaphore will be held in read mode for the duration of fault
processing, and held in write mode for unmap operations which may call
huge_pmd_unshare. Acquiring i_mmap_rwsem is also still required to
synchronize huge pmd sharing. However it is only required in the fault
path when setting up sharing, and will be acquired in huge_pmd_share().
Patch 6 adds the new vma lock and all supporting routines, but does not
actually change code to use the new lock.
Patch 7 refactors code in preparation for using the new lock. And, patch
8 finally adds code to make use of this new vma lock. Unfortunately, the
fault code and truncate/hole punch code would naturally take locks in the
opposite order which could lead to deadlock. Since the performance of
page faults is more important, the truncation/hole punch code is modified
to back out and take locks in the correct order if necessary.
[1] https://lore.kernel.org/linux-mm/43faf292-245b-5db5-cce9-369d8fb6bd21@infradead.org/
[2] https://lore.kernel.org/lkml/20200622005551.GK5535@shao2-debian/
[3] https://lore.kernel.org/linux-mm/20200706202615.32111-1-mike.kravetz@oracle.com/
This patch (of 9):
Commit c0d0381ade ("hugetlbfs: use i_mmap_rwsem for more pmd sharing
synchronization") added code to take i_mmap_rwsem in read mode for the
duration of fault processing. The use of i_mmap_rwsem to prevent
fault/truncate races depends on this. However, this has been shown to
cause performance/scaling issues. As a result, that code will be
reverted. Since the use i_mmap_rwsem to address page fault/truncate races
depends on this, it must also be reverted.
In a subsequent patch, code will be added to detect the fault/truncate
race and back out operations as required.
Link: https://lkml.kernel.org/r/20220914221810.95771-1-mike.kravetz@oracle.com
Link: https://lkml.kernel.org/r/20220914221810.95771-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: James Houghton <jthoughton@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
NFSv4 mandates a change attribute to avoid problems with timestamp
granularity, which Linux implements using the i_version counter. This is
particularly important when the underlying filesystem is fast.
Give tmpfs an i_version counter. Since it doesn't have to be persistent,
we can just turn on SB_I_VERSION and sprinkle some inode_inc_iversion
calls in the right places.
Also, while there is no formal spec for xattrs, most implementations
update the ctime on setxattr. Fix shmem_xattr_handler_set to update the
ctime and bump the i_version appropriately.
Link: https://lkml.kernel.org/r/20220909130031.15477-1-jlayton@kernel.org
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Changed .iterate to .iterate_shared in orangefs_dir_operations. I
didn't change anything else, there were no xfstests regressions
and no problem with any of my other tests...
Signed-off-by: Mike Marshall <hubcap@omnibond.com>
We want to ensure that the server never misses the layout stats when
we're closing the file, so that it knows whether or not to update its
internal state. Otherwise, if we were racing with a layout stat, we
might cause the server to invalidate its layout before the layout stat
got processed.
Fixes: 06946c6a3d ("pNFS/flexfiles: Only send layoutstats updates for mirrors that were updated")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Commit 064109db53 ("NFS: remove redundant code in nfs_file_write()")
identifies that filemap_fdatawait_range() will always return 0 and removes
a dead error-handling case in nfs_file_write(). With this change however,
assigning the return of filemap_fdatawait_range() to the result variable is
a dead store.
Remove this needless assignment.
No functional change. No change in object code.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Use ida_alloc()/ida_free() instead of
ida_simple_get()/ida_simple_remove().
The latter is deprecated and more verbose.
Signed-off-by: Bo Liu <liubo03@inspur.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Add a new tracepoint so we can see what mapping the filesystem returns
to writeback a dirty page.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
For scan loop must ensure that at least EXT4_FC_TAG_BASE_LEN space. If remain
space less than EXT4_FC_TAG_BASE_LEN which will lead to out of bound read
when mounting corrupt file system image.
ADD_RANGE/HEAD/TAIL is needed to add extra check when do journal scan, as this
three tags will read data during scan, tag length couldn't less than data length
which will read.
Cc: stable@kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Link: https://lore.kernel.org/r/20220924075233.2315259-4-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Now we load the super block from the disk in two steps. First we load
the super block with the default block size(EXT4_MIN_BLOCK_SIZE). Second
we load the super block with the real block size. The second step is a
little far from the first step. This patch move these two steps together
in a new function.
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220916141527.1012715-15-yanaijie@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
