linux.git/mm/frontswap.c, branch master

mm: kill frontswap

2023-08-21T20:37:26+00:00

The only user of frontswap is zswap, and has been for a long time.  Have
swap call into zswap directly and remove the indirection.

[hannes@cmpxchg.org: remove obsolete comment, per Yosry]
  Link: https://lkml.kernel.org/r/20230719142832.GA932528@cmpxchg.org
[fengwei.yin@intel.com: don't warn if none swapcache folio is passed to zswap_load]
  Link: https://lkml.kernel.org/r/20230810095652.3905184-1-fengwei.yin@intel.com
Link: https://lkml.kernel.org/r/20230717160227.GA867137@cmpxchg.org
Signed-off-by: Johannes Weiner 
Signed-off-by: Yin Fengwei 
Acked-by: Konrad Rzeszutek Wilk 
Acked-by: Nhat Pham 
Acked-by: Yosry Ahmed 
Acked-by: Christoph Hellwig 
Cc: Domenico Cerasuolo 
Cc: Matthew Wilcox (Oracle) 
Cc: Vitaly Wool 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

mm: zswap: support exclusive loads

2023-06-19T23:19:05+00:00

Commit 71024cb4a0bf ("frontswap: remove frontswap_tmem_exclusive_gets")
removed support for exclusive loads from frontswap as it was not used. 
Bring back exclusive loads support to frontswap by adding an "exclusive"
output parameter to frontswap_ops->load.

On the zswap side, add a module parameter to enable/disable exclusive
loads, and a config option to control the boot default value.  Refactor
zswap entry invalidation in zswap_frontswap_invalidate_page() into
zswap_invalidate_entry() to reuse it in zswap_frontswap_load() if
exclusive loads are enabled.

With exclusive loads, we avoid having two copies of the same page in
memory (compressed & uncompressed) after faulting it in from zswap.  On
the other hand, if the page is to be reclaimed again without being
dirtied, it will be re-compressed.  Compression is not usually slow, and a
page that was just faulted in is less likely to be reclaimed again soon.

Link: https://lkml.kernel.org/r/20230607195143.1473802-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed 
Suggested-by: Yu Zhao 
Acked-by: Johannes Weiner 
Cc: Dan Streetman 
Cc: Domenico Cerasuolo 
Cc: Konrad Rzeszutek Wilk 
Cc: Nhat Pham 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton

frontswap: don't call ->init if no ops are registered

2022-09-26T19:14:34+00:00

If no frontswap module (i.e.  zswap) was registered, frontswap_ops will be
NULL.  In such situation, swapon crashes with the following stack trace:

  Unable to handle kernel access to user memory outside uaccess routines at virtual address 0000000000000000
  Mem abort info:
    ESR = 0x0000000096000004
    EC = 0x25: DABT (current EL), IL = 32 bits
    SET = 0, FnV = 0
    EA = 0, S1PTW = 0
    FSC = 0x04: level 0 translation fault
  Data abort info:
    ISV = 0, ISS = 0x00000004
    CM = 0, WnR = 0
  user pgtable: 4k pages, 48-bit VAs, pgdp=00000020a4fab000
  [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
  Internal error: Oops: 96000004 [#1] SMP
  Modules linked in: zram fsl_dpaa2_eth pcs_lynx phylink ahci_qoriq crct10dif_ce ghash_ce sbsa_gwdt fsl_mc_dpio nvme lm90 nvme_core at803x xhci_plat_hcd rtc_fsl_ftm_alarm xgmac_mdio ahci_platform i2c_imx ip6_tables ip_tables fuse
  Unloaded tainted modules: cppc_cpufreq():1
  CPU: 10 PID: 761 Comm: swapon Not tainted 6.0.0-rc2-00454-g22100432cf14 #1
  Hardware name: SolidRun Ltd. SolidRun CEX7 Platform, BIOS EDK II Jun 21 2022
  pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  pc : frontswap_init+0x38/0x60
  lr : __do_sys_swapon+0x8a8/0x9f4
  sp : ffff80000969bcf0
  x29: ffff80000969bcf0 x28: ffff37bee0d8fc00 x27: ffff80000a7f5000
  x26: fffffcdefb971e80 x25: ffffaba797453b90 x24: 0000000000000064
  x23: ffff37c1f209d1a8 x22: ffff37bee880e000 x21: ffffaba797748560
  x20: ffff37bee0d8fce4 x19: ffffaba797748488 x18: 0000000000000014
  x17: 0000000030ec029a x16: ffffaba795a479b0 x15: 0000000000000000
  x14: 0000000000000000 x13: 0000000000000030 x12: 0000000000000001
  x11: ffff37c63c0aba18 x10: 0000000000000000 x9 : ffffaba7956b8c88
  x8 : ffff80000969bcd0 x7 : 0000000000000000 x6 : 0000000000000000
  x5 : 0000000000000001 x4 : 0000000000000000 x3 : ffffaba79730f000
  x2 : ffff37bee0d8fc00 x1 : 0000000000000000 x0 : 0000000000000000
  Call trace:
  frontswap_init+0x38/0x60
  __do_sys_swapon+0x8a8/0x9f4
  __arm64_sys_swapon+0x28/0x3c
  invoke_syscall+0x78/0x100
  el0_svc_common.constprop.0+0xd4/0xf4
  do_el0_svc+0x38/0x4c
  el0_svc+0x34/0x10c
  el0t_64_sync_handler+0x11c/0x150
  el0t_64_sync+0x190/0x194
  Code: d000e283 910003fd f9006c41 f946d461 (f9400021)
  ---[ end trace 0000000000000000 ]---

Link: https://lkml.kernel.org/r/20220909130829.3262926-1-hch@lst.de
Fixes: 1da0d94a3ec8 ("frontswap: remove support for multiple ops")
Reported-by: Nathan Chancellor 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Liu Shixin 
Cc: Konrad Rzeszutek Wilk 
Cc: 
Signed-off-by: Andrew Morton

docs: rename Documentation/vm to Documentation/mm

2022-06-27T19:52:53+00:00

so it will be consistent with code mm directory and with
Documentation/admin-guide/mm and won't be confused with virtual machines.

Signed-off-by: Mike Rapoport 
Suggested-by: Matthew Wilcox 
Tested-by: Ira Weiny 
Acked-by: Jonathan Corbet 
Acked-by: Wu XiangCheng

frontswap: remove support for multiple ops

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

There is only a single instance of frontswap ops in the kernel, so
simplify the frontswap code by removing support for multiple operations.

Link: https://lkml.kernel.org/r/20211224062246.1258487-13-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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: simplify frontswap_register_ops

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

Given that frontswap_register_ops must be called from built-in code,
there is no need to handle the case of swapfiles coming online before or
during it, so delete the code that deals with that case.

Link: https://lkml.kernel.org/r/20211224062246.1258487-11-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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove frontswap_test

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

frontswap_test is unused now, remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-10-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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove the frontswap exports

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

None of the frontswap API is called from modular code.

Link: https://lkml.kernel.org/r/20211224062246.1258487-8-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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: simplify frontswap_init

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

Just use IS_ENABLED() and remove the __frontswap_init indirection.

Also remove the unused export.

Link: https://lkml.kernel.org/r/20211224062246.1258487-7-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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove frontswap_curr_pages

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

frontswap_curr_pages is never called, so remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-6-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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds