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linux/mm
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Brian Foster 52aecaee1c mm: zero range of eof folio exposed by inode size extension 
On some filesystems, it is currently possible to create a transient
data inconsistency between pagecache and on-disk state. For example,
on a 1k block size ext4 filesystem:

$ xfs_io -fc "pwrite 0 2k" -c "mmap 0 4k" -c "mwrite 2k 2k" \
	  -c "truncate 8k" -c "fiemap -v" -c "pread -v 2k 16" <file>
...
 EXT: FILE-OFFSET      BLOCK-RANGE      TOTAL FLAGS
   0: [0..3]:          17410..17413         4   0x1
   1: [4..15]:         hole                12
00000800:  58 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58  XXXXXXXXXXXXXXXX
$ umount <mnt>; mount <dev> <mnt>
$ xfs_io -c "pread -v 2k 16" <file>
00000800:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

This allocates and writes two 1k blocks, map writes to the post-eof
portion of the (4k) eof folio, extends the file, and then shows that
the post-eof data is not cleared before the file size is extended.
The result is pagecache with a clean and uptodate folio over a hole
that returns non-zero data. Once reclaimed, pagecache begins to
return valid data.

Some filesystems avoid this problem by flushing the EOF folio before
inode size extension. This triggers writeback time partial post-eof
zeroing. XFS explicitly zeroes newly exposed file ranges via
iomap_zero_range(), but this includes a hack to flush dirty but
hole-backed folios, which means writeback actually does the zeroing
in this particular case as well. bcachefs explicitly flushes the eof
folio on truncate extension to the same effect, but doesn't handle
the analogous write extension case (i.e., replace "truncate 8k" with
"pwrite 4k 4k" in the above example command to reproduce the same
problem on bcachefs). btrfs doesn't seem to support subpage block
sizes.

The two main options to avoid this behavior are to either flush or
do the appropriate zeroing during size extending operations. Zeroing
is only required when the size change exposes ranges of the file
that haven't been directly written, such as a write or truncate that
starts beyond the current eof. The pagecache_isize_extended() helper
is already used for this particular scenario. It currently cleans
any pte's for the eof folio to ensure preexisting mappings fault and
allow the filesystem to take action based on the updated inode size.
This is required to ensure the folio is fully backed by allocated
blocks, for example, but this also happens to be the same scenario
zeroing is required.

Update pagecache_isize_extended() to zero the post-eof range of the
eof folio if it is dirty at the time of the size change, since
writeback now won't have the chance. If non-dirty, the folio has
either not been written or the post-eof portion was zeroed by
writeback.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Link: https://patch.msgid.link/20240919160741.208162-3-bfoster@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2024-11-12 23:54:14 -05:00
..
damon mm/damon/tests/sysfs-kunit.h: fix memory leak in damon_sysfs_test_add_targets() 2024-10-17 00:28:08 -07:00
kasan Rust changes for v6.12 2024-09-25 10:25:40 -07:00
kfence mm: kfence: fix elapsed time for allocated/freed track 2024-09-26 14:01:44 -07:00
kmsan kmsan: do not pass NULL pointers as 0 2024-07-03 19:30:26 -07:00
backing-dev.c writeback: support retrieving per group debug writeback stats of bdi 2024-05-05 17:53:51 -07:00
balloon_compaction.c mm: remove MIGRATE_SYNC_NO_COPY mode 2024-07-03 19:30:00 -07:00
bootmem_info.c bootmem: use kmemleak_free_part_phys in put_page_bootmem 2023-10-25 16:47:13 -07:00
cma_debug.c
cma_sysfs.c mm/cma: add sysfs file 'release_pages_success' 2024-02-22 10:24:57 -08:00
cma.c mm/cma: add cma_{alloc,free}_folio() 2024-09-03 21:15:36 -07:00
cma.h mm/cma: add sysfs file 'release_pages_success' 2024-02-22 10:24:57 -08:00
compaction.c mm:page_alloc: fix the NULL ac->nodemask in __alloc_pages_slowpath() 2024-09-03 21:15:47 -07:00
debug_page_alloc.c mm: page_alloc: consolidate free page accounting 2024-04-25 20:56:04 -07:00
debug_page_ref.c
debug_vm_pgtable.c mm/debug_vm_pgtable: Use pxdp_get() for accessing page table entries 2024-09-17 01:07:01 -07:00
debug.c mm: support only one page_type per page 2024-09-03 21:15:43 -07:00
dmapool_test.c mm/dmapool: add MODULE_DESCRIPTION() 2024-07-03 19:29:58 -07:00
dmapool.c mm/mempool/dmapool: remove CONFIG_DEBUG_SLAB ifdefs 2023-12-05 11:17:58 +01:00
early_ioremap.c
execmem.c mm/execmem, arch: convert remaining overrides of module_alloc to execmem 2024-05-14 00:31:43 -07:00
fadvise.c introduce fd_file(), convert all accessors to it. 2024-08-12 22:00:43 -04:00
fail_page_alloc.c fault-inject: improve build for CONFIG_FAULT_INJECTION=n 2024-09-01 20:43:33 -07:00
failslab.c fault-inject: improve build for CONFIG_FAULT_INJECTION=n 2024-09-01 20:43:33 -07:00
filemap.c mm/filemap: fix filemap_get_folios_contig THP panic 2024-09-26 14:01:43 -07:00
folio-compat.c mm: remove putback_lru_page() 2024-09-09 16:38:59 -07:00
gup_test.c
gup_test.h
gup.c mm/hugetlb: simplify refs in memfd_alloc_folio 2024-09-26 14:01:44 -07:00
highmem.c mm/highmem: make nr_free_highpages() return "unsigned long" 2024-07-03 19:30:06 -07:00
hmm.c mm: provide mm_struct and address to huge_ptep_get() 2024-07-12 15:52:15 -07:00
huge_memory.c mm: huge_memory: add vma_thp_disabled() and thp_disabled_by_hw() 2024-10-17 00:28:10 -07:00
hugetlb_cgroup.c mm: memcg: don't call propagate_protected_usage() needlessly 2024-09-01 20:25:50 -07:00
hugetlb_vmemmap.c mm/hugetlb_vmemmap: don't synchronize_rcu() without HVO 2024-09-01 20:25:45 -07:00
hugetlb_vmemmap.h mm: hugetlb_vmemmap: fix reference to nonexistent file 2023-10-25 16:47:14 -07:00
hugetlb.c mm/hugetlb: fix memfd_pin_folios resv_huge_pages leak 2024-09-26 14:01:43 -07:00
hwpoison-inject.c mm/hwpoison: add MODULE_DESCRIPTION() 2024-07-03 19:29:58 -07:00
init-mm.c mm: Deprecate pasid field 2023-12-12 10:11:32 +01:00
internal.h ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
interval_tree.c
io-mapping.c
ioremap.c
Kconfig mm: make SPLIT_PTE_PTLOCKS depend on SMP 2024-09-26 14:01:43 -07:00
Kconfig.debug slub: Introduce CONFIG_SLUB_RCU_DEBUG 2024-08-27 14:12:51 +02:00
khugepaged.c mm: khugepaged: fix the incorrect statistics when collapsing large file folios 2024-10-17 00:28:10 -07:00
kmemleak.c mm/kmemleak: use IS_ERR_PCPU() for pointer in the percpu address space 2024-09-03 21:15:38 -07:00
ksm.c mm: remove PageSwapCache 2024-09-03 21:15:44 -07:00
list_lru.c mm: list_lru: fix UAF for memory cgroup 2024-08-07 18:33:56 -07:00
maccess.c
madvise.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
Makefile mm: introduce numa_emulation 2024-09-03 21:15:31 -07:00
mapping_dirty_helpers.c mm: fix clean_record_shared_mapping_range kernel-doc 2023-08-24 16:20:30 -07:00
memblock.c memblock: updates for 6.12-rc1 2024-09-25 11:35:19 -07:00
memcontrol-v1.c struct fd layout change (and conversion to accessor helpers) 2024-09-23 09:35:36 -07:00
memcontrol-v1.h memcg: cleanup with !CONFIG_MEMCG_V1 2024-09-17 01:07:00 -07:00
memcontrol.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
memfd.c mm/hugetlb: simplify refs in memfd_alloc_folio 2024-09-26 14:01:44 -07:00
memory_hotplug.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
memory-failure.c mm: migrate: add isolate_folio_to_list() 2024-09-03 21:15:59 -07:00
memory-tiers.c memory tiers: use default_dram_perf_ref_source in log message 2024-09-26 14:01:44 -07:00
memory.c mm: fix follow_pfnmap API lockdep assert 2024-10-18 09:50:05 -07:00
mempolicy.c mm,memcg: provide per-cgroup counters for NUMA balancing operations 2024-09-03 21:15:36 -07:00
mempool.c mm: fix xyz_noprof functions calling profiled functions 2024-06-05 19:19:26 -07:00
memremap.c mm: convert put_devmap_managed_page_refs() to put_devmap_managed_folio_refs() 2024-05-05 17:53:49 -07:00
memtest.c memtest: use {READ,WRITE}_ONCE in memory scanning 2024-03-13 12:12:21 -07:00
migrate_device.c mm: remap unused subpages to shared zeropage when splitting isolated thp 2024-09-09 16:39:03 -07:00
migrate.c mm: migrate: annotate data-race in migrate_folio_unmap() 2024-09-26 14:01:44 -07:00
mincore.c mm: provide mm_struct and address to huge_ptep_get() 2024-07-12 15:52:15 -07:00
mlock.c Random number generator updates for Linux 6.11-rc1. 2024-07-24 10:29:50 -07:00
mm_init.c mm: drop CONFIG_HAVE_ARCH_NODEDATA_EXTENSION 2024-09-03 21:15:28 -07:00
mm_slot.h
mmap_lock.c mm: mmap_lock: replace get_memcg_path_buf() with on-stack buffer 2024-07-03 19:30:26 -07:00
mmap.c mm/mmap: correct error handling in mmap_region() 2024-10-17 00:28:05 -07:00
mmu_gather.c mm/mmu_gather: improve cond_resched() handling with large folios and expensive page freeing 2024-02-22 15:27:17 -08:00
mmu_notifier.c mm: move internal core VMA manipulation functions to own file 2024-09-01 20:25:54 -07:00
mmzone.c mm: improve code consistency with zonelist_* helper functions 2024-09-01 20:25:55 -07:00
mprotect.c mm/mprotect: replace can_modify_mm with can_modify_vma 2024-09-03 21:15:41 -07:00
mremap.c mm/mremap: fix move_normal_pmd/retract_page_tables race 2024-10-17 00:28:07 -07:00
mseal.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
msync.c
nommu.c mm: remove follow_page() 2024-09-01 20:26:01 -07:00
numa_emulation.c mm: introduce numa_emulation 2024-09-03 21:15:31 -07:00
numa_memblks.c mm: make range-to-target_node lookup facility a part of numa_memblks 2024-09-03 21:15:32 -07:00
numa.c mm: make range-to-target_node lookup facility a part of numa_memblks 2024-09-03 21:15:32 -07:00
oom_kill.c memory: remove the now superfluous sentinel element from ctl_table array 2024-04-25 20:56:32 -07:00
page_alloc.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
page_counter.c mm, memcg: cg2 memory{.swap,}.peak write handlers 2024-09-01 20:25:53 -07:00
page_ext.c mm: don't account memmap per-node 2024-08-15 22:16:14 -07:00
page_idle.c
page_io.c mm: fix swap_read_folio_zeromap() for large folios with partial zeromap 2024-09-17 01:07:01 -07:00
page_isolation.c mm: remove migration for HugePage in isolate_single_pageblock() 2024-09-03 21:15:40 -07:00
page_owner.c mm/page-owner: use gfp_nested_mask() instead of open coded masking 2024-05-19 14:40:44 -07:00
page_poison.c mm/page_poison: replace kmap_atomic() with kmap_local_page() 2023-12-10 16:51:50 -08:00
page_reporting.c mm, treewide: rename MAX_ORDER to MAX_PAGE_ORDER 2024-01-08 15:27:15 -08:00
page_reporting.h
page_table_check.c mm/page_table_check: fix crash on ZONE_DEVICE 2024-06-15 10:43:04 -07:00
page_vma_mapped.c mm: make page_mapped_in_vma conditional on CONFIG_MEMORY_FAILURE 2024-05-05 17:53:45 -07:00
page-writeback.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
pagewalk.c mm/pagewalk: check pfnmap for folio_walk_start() 2024-09-17 01:06:58 -07:00
percpu-internal.h mm: remove CONFIG_MEMCG_KMEM 2024-07-10 12:14:54 -07:00
percpu-km.c
percpu-stats.c
percpu-vm.c percpu: clean up all mappings when pcpu_map_pages() fails 2024-04-25 20:55:49 -07:00
percpu.c percpu: remove pcpu_alloc_size() 2024-09-01 20:26:04 -07:00
pgalloc-track.h
pgtable-generic.c mm: fix race between __split_huge_pmd_locked() and GUP-fast 2024-05-07 10:37:00 -07:00
process_vm_access.c mm: fix process_vm_rw page counts 2023-12-10 16:51:39 -08:00
ptdump.c mm: ptdump: add check_wx_pages debugfs attribute 2024-02-22 10:24:47 -08:00
readahead.c struct fd layout change (and conversion to accessor helpers) 2024-09-23 09:35:36 -07:00
rmap.c mm: introduce a pageflag for partially mapped folios 2024-09-09 16:39:04 -07:00
rodata_test.c
secretmem.c secretmem: disable memfd_secret() if arch cannot set direct map 2024-10-09 12:47:19 -07:00
shmem_quota.c shmem_quota: build the object file conditionally to the config option 2024-09-01 20:25:45 -07:00
shmem.c mm: huge_memory: add vma_thp_disabled() and thp_disabled_by_hw() 2024-10-17 00:28:10 -07:00
show_mem.c mm/show_mem.c: report alloc tags in human readable units 2024-09-17 01:07:00 -07:00
shrinker_debug.c mm: shrinker: use min() to improve shrinker_debugfs_scan_write() 2024-09-03 21:15:40 -07:00
shrinker.c mm: shrinker: use kvzalloc_node() from expand_one_shrinker_info() 2024-01-05 09:58:32 -08:00
shuffle.c
shuffle.h mm, treewide: rename MAX_ORDER to MAX_PAGE_ORDER 2024-01-08 15:27:15 -08:00
slab_common.c mm, slab: suppress warnings in test_leak_destroy kunit test 2024-10-02 16:28:46 +02:00
slab.h mm, slab: suppress warnings in test_leak_destroy kunit test 2024-10-02 16:28:46 +02:00
slub.c mm, slab: suppress warnings in test_leak_destroy kunit test 2024-10-02 16:28:46 +02:00
sparse-vmemmap.c mm: don't account memmap per-node 2024-08-15 22:16:14 -07:00
sparse.c A set of X86 fixes: 2024-09-01 14:43:08 -07:00
swap_cgroup.c mm: attempt to batch free swap entries for zap_pte_range() 2024-09-03 21:15:33 -07:00
swap_slots.c mm: swap: update get_swap_pages() to take folio order 2024-04-25 20:56:37 -07:00
swap_state.c mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios 2024-09-17 01:07:01 -07:00
swap.c mm: remove isolate_lru_page() 2024-09-09 16:38:59 -07:00
swap.h mm: fix swap_read_folio_zeromap() for large folios with partial zeromap 2024-09-17 01:07:01 -07:00
swapfile.c mm/swapfile: skip HugeTLB pages for unuse_vma 2024-10-17 00:28:11 -07:00
truncate.c mm: zero range of eof folio exposed by inode size extension 2024-11-12 23:54:14 -05:00
usercopy.c
userfaultfd.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
util.c mm: only enforce minimum stack gap size if it's sensible 2024-09-01 20:26:02 -07:00
vma_internal.h mm: remove duplicated include in vma_internal.h 2024-09-01 20:26:02 -07:00
vma.c mm/vma: return the exact errno in vms_gather_munmap_vmas() 2024-09-17 01:07:00 -07:00
vma.h mm: make vma_prepare() and friends static and internal to vma.c 2024-09-03 21:15:54 -07:00
vmalloc.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
vmpressure.c eventfd: simplify eventfd_signal() 2023-11-28 14:08:38 +01:00
vmscan.c mm/mglru: only clear kswapd_failures if reclaimable 2024-10-17 00:28:12 -07:00
vmstat.c mm: split underused THPs 2024-09-09 16:39:04 -07:00
workingset.c cachestat: do not flush stats in recency check 2024-07-03 22:40:37 -07:00
z3fold.c mm/z3fold: add __percpu annotation to *unbuddied pointer in struct z3fold_pool 2024-09-01 20:25:56 -07:00
zbud.c mm: zpool: return pool size in pages 2024-04-25 20:55:48 -07:00
zpool.c mm: zpool: return pool size in pages 2024-04-25 20:55:48 -07:00
zsmalloc.c ALong with the usual shower of singleton patches, notable patch series in 2024-09-21 07:29:05 -07:00
zswap.c mm: zswap: delete comments for "value" member of 'struct zswap_entry'. 2024-10-09 12:47:19 -07:00