linux.git/mm/page-writeback.c, branch v6.11

sysctl: treewide: constify the ctl_table argument of proc_handlers

2024-07-24T18:59:29+00:00

const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.

This patch has been generated by the following coccinelle script:

```
  virtual patch

  @r1@
  identifier ctl, write, buffer, lenp, ppos;
  identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

  @r2@
  identifier func, ctl, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos)
  { ... }

  @r3@
  identifier func;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int , void *, size_t *, loff_t *);

  @r4@
  identifier func, ctl;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int , void *, size_t *, loff_t *);

  @r5@
  identifier func, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

```

* Code formatting was adjusted in xfs_sysctl.c to comply with code
  conventions. The xfs_stats_clear_proc_handler,
  xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
  adjusted.

* The ctl_table argument in proc_watchdog_common was const qualified.
  This is called from a proc_handler itself and is calling back into
  another proc_handler, making it necessary to change it as part of the
  proc_handler migration.

Co-developed-by: Thomas Weißschuh 
Signed-off-by: Thomas Weißschuh 
Co-developed-by: Joel Granados 
Signed-off-by: Joel Granados

mm: avoid overflows in dirty throttling logic

2024-07-04T02:30:15+00:00

The dirty throttling logic is interspersed with assumptions that dirty
limits in PAGE_SIZE units fit into 32-bit (so that various multiplications
fit into 64-bits).  If limits end up being larger, we will hit overflows,
possible divisions by 0 etc.  Fix these problems by never allowing so
large dirty limits as they have dubious practical value anyway.  For
dirty_bytes / dirty_background_bytes interfaces we can just refuse to set
so large limits.  For dirty_ratio / dirty_background_ratio it isn't so
simple as the dirty limit is computed from the amount of available memory
which can change due to memory hotplug etc.  So when converting dirty
limits from ratios to numbers of pages, we just don't allow the result to
exceed UINT_MAX.

This is root-only triggerable problem which occurs when the operator
sets dirty limits to >16 TB.

Link: https://lkml.kernel.org/r/20240621144246.11148-2-jack@suse.cz
Signed-off-by: Jan Kara 
Reported-by: Zach O'Keefe 
Reviewed-By: Zach O'Keefe 
Cc: 
Signed-off-by: Andrew Morton

Revert "mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again"

2024-07-04T02:30:15+00:00

Patch series "mm: Avoid possible overflows in dirty throttling".

Dirty throttling logic assumes dirty limits in page units fit into
32-bits.  This patch series makes sure this is true (see patch 2/2 for
more details).


This patch (of 2):

This reverts commit 9319b647902cbd5cc884ac08a8a6d54ce111fc78.

The commit is broken in several ways.  Firstly, the removed (u64) cast
from the multiplication will introduce a multiplication overflow on 32-bit
archs if wb_thresh * bg_thresh >= 1<<32 (which is actually common - the
default settings with 4GB of RAM will trigger this).  Secondly, the
div64_u64() is unnecessarily expensive on 32-bit archs.  We have
div64_ul() in case we want to be safe & cheap.  Thirdly, if dirty
thresholds are larger than 1<<32 pages, then dirty balancing is going to
blow up in many other spectacular ways anyway so trying to fix one
possible overflow is just moot.

Link: https://lkml.kernel.org/r/20240621144017.30993-1-jack@suse.cz
Link: https://lkml.kernel.org/r/20240621144246.11148-1-jack@suse.cz
Fixes: 9319b647902c ("mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again")
Signed-off-by: Jan Kara 
Reviewed-By: Zach O'Keefe 
Cc: 
Signed-off-by: Andrew Morton

writeback: factor out balance_wb_limits to remove repeated code

2024-07-04T02:29:54+00:00

Factor out balance_wb_limits to remove repeated code

[shikemeng@huaweicloud.com: add comment]
  Link: https://lkml.kernel.org/r/20240606033547.344376-1-shikemeng@huaweicloud.com
[akpm@linux-foundation.org: s/fileds/fields/ in comment]
Link: https://lkml.kernel.org/r/20240514125254.142203-9-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi 
Cc: Matthew Wilcox (Oracle) 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton

writeback: factor out wb_dirty_exceeded to remove repeated code

2024-07-04T02:29:54+00:00

Factor out wb_dirty_exceeded to remove repeated code

Link: https://lkml.kernel.org/r/20240514125254.142203-8-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi 
Acked-by: Tejun Heo 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

writeback: factor out balance_domain_limits to remove repeated code

2024-07-04T02:29:54+00:00

Factor out balance_domain_limits to remove repeated code.

Link: https://lkml.kernel.org/r/20240514125254.142203-7-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi 
Acked-by: Tejun Heo 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

writeback: factor out wb_dirty_freerun to remove more repeated freerun code

2024-07-04T02:29:54+00:00

Factor out wb_dirty_freerun to remove more repeated freerun code.

Link: https://lkml.kernel.org/r/20240514125254.142203-6-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi 
Acked-by: Tejun Heo 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

writeback: factor out code of freerun to remove repeated code

2024-07-04T02:29:54+00:00

Factor out code of freerun into new helper functions domain_poll_intv and
domain_dirty_freerun to remove repeated code.

Link: https://lkml.kernel.org/r/20240514125254.142203-5-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi 
Acked-by: Tejun Heo 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

writeback: factor out domain_over_bg_thresh to remove repeated code

2024-07-04T02:29:54+00:00

Factor out domain_over_bg_thresh from wb_over_bg_thresh to remove repeated
code.

Link: https://lkml.kernel.org/r/20240514125254.142203-4-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi 
Acked-by: Tejun Heo 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

writeback: add general function domain_dirty_avail to calculate dirty and avail of domain

2024-07-04T02:29:53+00:00

Add general function domain_dirty_avail to calculate dirty and avail for
either dirty limit or background writeback in either global domain or wb
domain.

Link: https://lkml.kernel.org/r/20240514125254.142203-3-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi 
Acked-by: Tejun Heo 
Cc: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton