fscache: Fix hanging wait on page discarded by writeback

[Daniel Axtens]

== SRU Justification ==

[Impact]
Under heavy NFS + FSCache load, a user sometimes observes a hang in __fscache_wait_on_page_write+0x5f/0xa0.

Example traces:
[<ffffffffc009f1bf>] __fscache_wait_on_page_write+0x5f/0xa0 [fscache]
[<ffffffffc009f6da>] __fscache_uncache_all_inode_pages+0xba/0x120 [fscache]
[<ffffffffc0419ece>] nfs_fscache_open_file+0x4e/0xc0 [nfs]

[<ffffffffc034f1bf>] __fscache_wait_on_page_write+0x5f/0xa0 [fscache]
[<ffffffffc04104dc>] __nfs_fscache_invalidate_page+0x2c/0x80 [nfs]
[<ffffffffc03fb543>] nfs_invalidate_page+0x63/0x90 [nfs]
[<ffffffff811925c0>] truncate_inode_page+0x80/0x90

[Fix]
Cherry-pick 2c98425720233ae3e135add0c7e869b32913502f from upstream, which is a patch from the FSCache maintainer.

[Testcase]
The user has run a NFS stress-test with a similar home-grown patch, and will run a stress test on the proposed kernel.

[Regression Potential]
Patch is limited to FSCache, so regression potential is limited.

[Dan Streetman (ddstreet)]

Note, this merged into Xenial via bug 1775771 by standard upstream stable merge process; it landed in Xenial commit 25ef67b828ea16b768ce2c549c2c92b9cad79ceb which is included starting at kernel 4.4.0-129.155.

[Dan Streetman (ddstreet)]

marking fix released for Xenial, based on explanation above.

[Andy Whitcroft (apw)]

This bug was nominated against a series that is no longer supported, ie artful. The bug task representing the artful nomination is being closed as Won't Fix.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Brad Figg (brad-figg)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-trusty' to 'verification-done-trusty'. If the problem still exists, change the tag 'verification-needed-trusty' to 'verification-failed-trusty'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Brad Figg (brad-figg)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.15.0-33.36

---------------
linux (4.15.0-33.36) bionic; urgency=medium

  * linux: 4.15.0-33.36 -proposed tracker (LP: #1787149)

  * RTNL assertion failure on ipvlan (LP: #1776927)
    - ipvlan: drop ipv6 dependency
    - ipvlan: use per device spinlock to protect addrs list updates
    - SAUCE: fix warning from "ipvlan: drop ipv6 dependency"

  * ubuntu_bpf_jit test failed on Bionic s390x systems (LP: #1753941)
    - test_bpf: flag tests that cannot be jited on s390

  * HDMI/DP audio can't work on the laptop of Dell Latitude 5495 (LP: #1782689)
    - drm/nouveau: fix nouveau_dsm_get_client_id()'s return type
    - drm/radeon: fix radeon_atpx_get_client_id()'s return type
    - drm/amdgpu: fix amdgpu_atpx_get_client_id()'s return type
    - platform/x86: apple-gmux: fix gmux_get_client_id()'s return type
    - ALSA: hda: use PCI_BASE_CLASS_DISPLAY to replace PCI_CLASS_DISPLAY_VGA
    - vga_switcheroo: set audio client id according to bound GPU id

  * locking sockets broken due to missing AppArmor socket mediation patches
    (LP: #1780227)
    - UBUNTU SAUCE: apparmor: fix apparmor mediating locking non-fs, unix sockets

  * Update2 for ocxl driver (LP: #1781436)
    - ocxl: Fix page fault handler in case of fault on dying process

  * netns: unable to follow an interface that moves to another netns
    (LP: #1774225)
    - net: core: Expose number of link up/down transitions
    - dev: always advertise the new nsid when the netns iface changes
    - dev: advertise the new ifindex when the netns iface changes

  * [Bionic] Disk IO hangs when using BFQ as io scheduler (LP: #1780066)
    - block, bfq: fix occurrences of request finish method's old name
    - block, bfq: remove batches of confusing ifdefs
    - block, bfq: add requeue-request hook

  * HP ProBook 455 G5 needs mute-led-gpio fixup (LP: #1781763)
    - ALSA: hda: add mute led support for HP ProBook 455 G5

  * [Bionic] bug fixes to improve stability of the ThunderX2 i2c driver
    (LP: #1781476)
    - i2c: xlp9xx: Fix issue seen when updating receive length
    - i2c: xlp9xx: Make sure the transfer size is not more than
      I2C_SMBUS_BLOCK_SIZE

  * x86/kvm: fix LAPIC timer drift when guest uses periodic mode (LP: #1778486)
    - x86/kvm: fix LAPIC timer drift when guest uses periodic mode

  * Please include ax88179_178a and r8152 modules in d-i udeb (LP: #1771823)
    - [Config:] d-i: Add ax88179_178a and r8152 to nic-modules

  * Nvidia fails after switching its mode (LP: #1778658)
    - PCI: Restore config space on runtime resume despite being unbound

  * Kernel error "task zfs:pid blocked for more than 120 seconds" (LP: #1781364)
    - SAUCE: (noup) zfs to 0.7.5-1ubuntu16.3

  * CVE-2018-12232
    - PATCH 1/1] socket: close race condition between sock_close() and
      sockfs_setattr()

  * CVE-2018-10323
    - xfs: set format back to extents if xfs_bmap_extents_to_btree

  * change front mic location for more lenovo m7/8/9xx machines (LP: #1781316)
    - ALSA: hda/realtek - Fix the problem of two front mics on more machines
    - ALSA: hda/realtek - two more lenovo models need fixup of MIC_LOCATION

  * Cephfs + fscache: unab...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.13.0-157.207

---------------
linux (3.13.0-157.207) trusty; urgency=medium

  * linux: 3.13.0-157.207 -proposed tracker (LP: #1787982)

  * CVE-2017-5715 (Spectre v2 retpoline)
    - SAUCE: Fix "x86/retpoline/entry: Convert entry assembler indirect jumps"

  * CVE-2017-2583
    - KVM: x86: fix emulation of "MOV SS, null selector"

  * CVE-2017-7518
    - KVM: x86: fix singlestepping over syscall

  * CVE-2017-18270
    - KEYS: prevent creating a different user's keyrings

  * Update to upstream's implementation of Spectre v1 mitigation (LP: #1774181)
    - Documentation: Document array_index_nospec
    - array_index_nospec: Sanitize speculative array de-references
    - x86: Implement array_index_mask_nospec
    - x86: Introduce barrier_nospec
    - x86/get_user: Use pointer masking to limit speculation
    - x86/syscall: Sanitize syscall table de-references under speculation
    - vfs, fdtable: Prevent bounds-check bypass via speculative execution
    - nl80211: Sanitize array index in parse_txq_params
    - x86/spectre: Report get_user mitigation for spectre_v1
    - x86/kvm: Update spectre-v1 mitigation
    - nospec: Allow index argument to have const-qualified type
    - nospec: Move array_index_nospec() parameter checking into separate macro
    - nospec: Kill array_index_nospec_mask_check()
    - SAUCE: Replace osb() calls with array_index_nospec()
    - SAUCE: Rename osb() to barrier_nospec()
    - SAUCE: x86: Use barrier_nospec in arch/x86/um/asm/barrier.h

  * Prevent speculation on user controlled pointer (LP: #1775137)
    - x86: reorganize SMAP handling in user space accesses
    - x86: fix SMAP in 32-bit environments
    - x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec
    - x86/usercopy: Replace open coded stac/clac with __uaccess_{begin, end}
    - x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec

  * CVE-2016-10208
    - ext4: validate s_first_meta_bg at mount time
    - ext4: fix fencepost in s_first_meta_bg validation

  * CVE-2018-10323
    - xfs: set format back to extents if xfs_bmap_extents_to_btree

  * CVE-2017-16911
    - usbip: prevent vhci_hcd driver from leaking a socket pointer address

  * CVE-2018-13406
    - video: uvesafb: Fix integer overflow in allocation

  * CVE-2018-10877
    - ext4: verify the depth of extent tree in ext4_find_extent()

  * CVE-2018-10881
    - ext4: clear i_data in ext4_inode_info when removing inline data

  * CVE-2018-1092
    - ext4: fail ext4_iget for root directory if unallocated

  * CVE-2018-1093
    - ext4: fix block bitmap validation when bigalloc, ^flex_bg
    - ext4: add validity checks for bitmap block numbers

  * CVE-2018-12233
    - jfs: Fix inconsistency between memory allocation and ea_buf->max_size

  * CVE-2017-16912
    - usbip: fix stub_rx: get_pipe() to validate endpoint number

  * CVE-2018-10675
    - mm/mempolicy: fix use after free when calling get_mempolicy

  * CVE-2017-8831
    - saa7164: fix sparse warnings
    - saa7164: fix double fetch PCIe access condition

  * CVE-2017-16533
    - HID: usbhid: fix out-of-bounds bug

  * CVE-2017-16538
    - media: dvb-usb-v2: lmedm04: move ts2...

[Andy Whitcroft (apw)]

This bug was erroneously marked for verification in bionic; verification is not required and verification-needed-bionic is being removed.