[PATCH 4.12 94/99] Clarify (and fix) MAX_LFS_FILESIZE macros

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 4.12 94/99] Clarify (and fix) MAX_LFS_FILESIZE macros
Date	2017-08-28 11:10 +0200
Message-ID	<ujodt-3Ju-31@gated-at.bofh.it> (permalink)
References	<ujnhn-38X-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@linux-foundation.org>

commit 0cc3b0ec23ce4c69e1e890ed2b8d2fa932b14aad upstream.

We have a MAX_LFS_FILESIZE macro that is meant to be filled in by
filesystems (and other IO targets) that know they are 64-bit clean and
don't have any 32-bit limits in their IO path.

It turns out that our 32-bit value for that limit was bogus.  On 32-bit,
the VM layer is limited by the page cache to only 32-bit index values,
but our logic for that was confusing and actually wrong.  We used to
define that value to

	(((loff_t)PAGE_SIZE << (BITS_PER_LONG-1))-1)

which is actually odd in several ways: it limits the index to 31 bits,
and then it limits files so that they can't have data in that last byte
of a page that has the highest 31-bit index (ie page index 0x7fffffff).

Neither of those limitations make sense.  The index is actually the full
32 bit unsigned value, and we can use that whole full page.  So the
maximum size of the file would logically be "PAGE_SIZE << BITS_PER_LONG".

However, we do wan tto avoid the maximum index, because we have code
that iterates over the page indexes, and we don't want that code to
overflow.  So the maximum size of a file on a 32-bit host should
actually be one page less than the full 32-bit index.

So the actual limit is ULONG_MAX << PAGE_SHIFT.  That means that we will
not actually be using the page of that last index (ULONG_MAX), but we
can grow a file up to that limit.

The wrong value of MAX_LFS_FILESIZE actually caused problems for Doug
Nazar, who was still using a 32-bit host, but with a 9.7TB 2 x RAID5
volume.  It turns out that our old MAX_LFS_FILESIZE was 8TiB (well, one
byte less), but the actual true VM limit is one page less than 16TiB.

This was invisible until commit c2a9737f45e2 ("vfs,mm: fix a dead loop
in truncate_inode_pages_range()"), which started applying that
MAX_LFS_FILESIZE limit to block devices too.

NOTE! On 64-bit, the page index isn't a limiter at all, and the limit is
actually just the offset type itself (loff_t), which is signed.  But for
clarity, on 64-bit, just use the maximum signed value, and don't make
people have to count the number of 'f' characters in the hex constant.

So just use LLONG_MAX for the 64-bit case.  That was what the value had
been before too, just written out as a hex constant.

Fixes: c2a9737f45e2 ("vfs,mm: fix a dead loop in truncate_inode_pages_range()")
Reported-and-tested-by: Doug Nazar <nazard@nazar.ca>
Cc: Andreas Dilger <adilger@dilger.ca>
Cc: Mark Fasheh <mfasheh@versity.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Dave Kleikamp <shaggy@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/linux/fs.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -891,9 +891,9 @@ static inline struct file *get_file(stru
 /* Page cache limit. The filesystems should put that into their s_maxbytes 
    limits, otherwise bad things can happen in VM. */ 
 #if BITS_PER_LONG==32
-#define MAX_LFS_FILESIZE	(((loff_t)PAGE_SIZE << (BITS_PER_LONG-1))-1)
+#define MAX_LFS_FILESIZE	((loff_t)ULONG_MAX << PAGE_SHIFT)
 #elif BITS_PER_LONG==64
-#define MAX_LFS_FILESIZE 	((loff_t)0x7fffffffffffffffLL)
+#define MAX_LFS_FILESIZE 	((loff_t)LLONG_MAX)
 #endif
 
 #define FL_POSIX	1

Thread

[PATCH 4.12 00/99] 4.12.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 90/99] iio: magnetometer: st_magn: fix status register address for LSM303AGR Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 23/99] irda: do not leak initialized list.dev to userspace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 40/99] ALSA: firewire: fix NULL pointer dereference when releasing uninitialized data of iso-resource Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 38/99] ALSA: core: Fix unexpected error at replacing user TLV Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 20/99] ipv6: repair fib6 tree in failure case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 44/99] ARCv2: PAE40: set MSB even if !CONFIG_ARC_HAS_PAE40 but PAE exists in SoC Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 17/99] sctp: fully initialize the IPv6 address in sctp_v6_to_addr() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 68/99] cifs: Fix df output for users with quota limits Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 11/99] net: igmp: Use ingress interface rather than vrf device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 18/99] tipc: fix use-after-free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 13/99] ptr_ring: use kmalloc_array() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 36/99] KVM: x86: block guest protection keys unless the host has them enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 31/99] Input: ALPS - fix two-finger scroll breakage in right side on ALPS touchpad Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 10/99] bpf: fix bpf_trace_printk on 32 bit archs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 93/99] iommu: Fix wrong freeing of iommu_device->dev Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 75/99] timers: Fix excessive granularity of new timers after a nohz idle Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 79/99] netfilter: nat: fix src map lookup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 77/99] net: sunrpc: svcsock: fix NULL-pointer exception Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 99/99] powerpc/mm: Ensure cpumask update is ordered Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 81/99] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 91/99] iio: magnetometer: st_magn: remove ihl property for LSM303AGR Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 76/99] x86/mm: Fix use-after-free of ldt_struct Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 80/99] netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 69/99] cifs: return ENAMETOOLONG for overlong names in cifs_open()/cifs_lookup() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 96/99] ntb: transport shouldnt disable link due to bogus values in SPADs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 89/99] iio: hid-sensor-trigger: Fix the race with user space powering up sensors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 73/99] ftrace: Check for null ret_stack on profile function graph entry function Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 95/99] ntb: ntb_test: ensure the link is up before trying to configure the mws Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 63/99] tracing: Missing error code in tracer_alloc_buffers() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 82/99] Bluetooth: cmtp: fix possible might sleep error in cmtp_session Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 94/99] Clarify (and fix) MAX_LFS_FILESIZE macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 74/99] perf/core: Fix group {cpu,task} validation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 71/99] ring-buffer: Have ring_buffer_alloc_read_page() return error on offline CPU Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 35/99] KVM, pkeys: do not use PKRU value in vcpu->arch.guest_fpu.state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 83/99] Bluetooth: bnep: fix possible might sleep error in bnep_session Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 72/99] virtio_pci: fix cpu affinity support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 97/99] ACPI: APD: Fix HID for Hisilicon Hip07/08 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 87/99] ANDROID: binder: fix proc->tsk check. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 37/99] ALSA: usb-audio: Add delay quirk for H650e/Jabra 550a USB headsets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 85/99] binder: use group leader instead of open thread Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 78/99] netfilter: expect: fix crash when putting uninited expectation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 98/99] ACPI: EC: Fix regression related to wrong ECDT initialization order Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 70/99] nfsd: Limit end of page list when decoding NFSv4 WRITE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 39/99] ALSA: hda - Add stereo mic quirk for Lenovo G50-70 (17aa:3978) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 33/99] KVM: s390: sthyi: fix specification exception detection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 64/99] tracing: Fix kmemleak in tracing_map_array_free() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 52/99] arm64: fpsimd: Prevent registers leaking across exec Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 03/99] bonding: ratelimit failed speed/duplex update warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 07/99] ipv4: fix NULL dereference in free_fib_info_rcu() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 47/99] dax: fix deadlock due to misaligned PMD faults Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 57/99] drm/atomic: If the atomic check fails, return its value first Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 45/99] PM/hibernate: touch NMI watchdog when creating snapshot Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 43/99] ARCv2: PAE40: Explicitly set MSB counterpart of SLC region ops addresses Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 08/99] net_sched/sfq: update hierarchical backlog when drop packet Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 61/99] ACPI: device property: Fix node lookup in acpi_graph_get_child_prop_value() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 48/99] i2c: designware: Fix system suspend Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 66/99] RDMA/uverbs: Initialize cq_context appropriately Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 30/99] Input: elan_i2c - add ELAN0602 ACPI ID to support Lenovo Yoga310 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 46/99] mm, shmem: fix handling /sys/kernel/mm/transparent_hugepage/shmem_enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 60/99] Revert "drm/amdgpu: fix vblank_time when displays are off" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 32/99] KVM: s390: sthyi: fix sthyi inline assembly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 09/99] net_sched: remove warning from qdisc_hash_add Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 65/99] tracing: Fix freeing of filter in create_filter() when set_str is false Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 41/99] ALSA: firewire-motu: destroy stream data surely at failure of card initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 05/99] dccp: purge write queue in dccp_destroy_sock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 42/99] ARCv2: SLC: Make sure busy bit is set properly for region ops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 49/99] mm/madvise.c: fix freeing of locked page with MADV_FREE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 21/99] tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 12/99] openvswitch: fix skb_panic due to the incorrect actions attrlen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 16/99] tun: handle register_netdevice() failures properly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 24/99] net: sched: fix NULL pointer dereference when action calls some targets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 02/99] bonding: require speed/duplex only for 802.3ad, alb and tlb Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 28/99] bpf/verifier: fix min/max handling in BPF_SUB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 26/99] bpf, verifier: add additional patterns to evaluate_reg_imm_alu Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 14/99] ipv4: better IP_MAX_MTU enforcement Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 19/99] ipv6: reset fn->rr_ptr when replacing route Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  Re: [PATCH 4.12 00/99] 4.12.10-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-08-28 21:50 +0200
    Re: [PATCH 4.12 00/99] 4.12.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-29 07:00 +0200
  Re: [PATCH 4.12 00/99] 4.12.10-stable review Guenter Roeck <linux@roeck-us.net> - 2017-08-29 02:20 +0200
    Re: [PATCH 4.12 00/99] 4.12.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-29 07:00 +0200

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