Commit 834f82e2 authored by Cyrill Gorcunov's avatar Cyrill Gorcunov Committed by Linus Torvalds
Browse files

procfs: add VmFlags field in smaps output 



During c/r sessions we've found that there is no way at the moment to
fetch some VMA associated flags, such as mlock() and madvise().

This leads us to a problem -- we don't know if we should call for mlock()
and/or madvise() after restore on the vma area we're bringing back to
life.

This patch intorduces a new field into "smaps" output called VmFlags,
where all set flags associated with the particular VMA is shown as two
letter mnemonics.

[ Strictly speaking for c/r we only need mlock/madvise bits but it has been
  said that providing just a few flags looks somehow inconsistent.  So all
  flags are here now. ]

This feature is made available on CONFIG_CHECKPOINT_RESTORE=n kernels, as
other applications may start to use these fields.

The data is encoded in a somewhat awkward two letters mnemonic form, to
encourage userspace to be prepared for fields being added or removed in
the future.

[a.p.zijlstra@chello.nl: props to use for_each_set_bit]
[sfr@canb.auug.org.au: props to use array instead of struct]
[akpm@linux-foundation.org: overall redesign and simplification]
[akpm@linux-foundation.org: remove unneeded braces per sfr, avoid using bloaty for_each_set_bit()]
Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7b9a7ec5

Documentation/filesystems/proc.txt

+38 −2
Original line number Diff line number Diff line
@@ -142,7 +142,7 @@ Table 1-1: Process specific entries in /proc 
 pagemap	Page table

 stack		Report full stack trace, enable via CONFIG_STACKTRACE

 smaps		a extension based on maps, showing the memory consumption of

		each mapping

		each mapping and flags associated with it

..............................................................................



For example, to get the status information of a process, all you have to do is
@@ -415,8 +415,9 @@ Swap: 0 kB 
KernelPageSize:        4 kB

MMUPageSize:           4 kB

Locked:              374 kB

VmFlags: rd ex mr mw me de



The first of these lines shows the same information as is displayed for the

the first of these lines shows the same information as is displayed for the

mapping in /proc/PID/maps.  The remaining lines show the size of the mapping

(size), the amount of the mapping that is currently resident in RAM (RSS), the

process' proportional share of this mapping (PSS), the number of clean and
@@ -430,6 +431,41 @@ and a page is modified, the file page is replaced by a private anonymous copy. 
"Swap" shows how much would-be-anonymous memory is also used, but out on

swap.



"VmFlags" field deserves a separate description. This member represents the kernel

flags associated with the particular virtual memory area in two letter encoded

manner. The codes are the following:

    rd  - readable

    wr  - writeable

    ex  - executable

    sh  - shared

    mr  - may read

    mw  - may write

    me  - may execute

    ms  - may share

    gd  - stack segment growns down

    pf  - pure PFN range

    dw  - disabled write to the mapped file

    lo  - pages are locked in memory

    io  - memory mapped I/O area

    sr  - sequential read advise provided

    rr  - random read advise provided

    dc  - do not copy area on fork

    de  - do not expand area on remapping

    ac  - area is accountable

    nr  - swap space is not reserved for the area

    ht  - area uses huge tlb pages

    nl  - non-linear mapping

    ar  - architecture specific flag

    dd  - do not include area into core dump

    mm  - mixed map area

    hg  - huge page advise flag

    nh  - no-huge page advise flag

    mg  - mergable advise flag



Note that there is no guarantee that every flag and associated mnemonic will

be present in all further kernel releases. Things get changed, the flags may

be vanished or the reverse -- new added.



This file is only present if the CONFIG_MMU kernel configuration option is

enabled.

fs/proc/task_mmu.c

+53 −0
Original line number Diff line number Diff line
@@ -526,6 +526,57 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 
	return 0;

}



static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)

{

	/*

	 * Don't forget to update Documentation/ on changes.

	 */

	static const char mnemonics[BITS_PER_LONG][2] = {

		/*

		 * In case if we meet a flag we don't know about.

		 */

		[0 ... (BITS_PER_LONG-1)] = "??",



		[ilog2(VM_READ)]	= "rd",

		[ilog2(VM_WRITE)]	= "wr",

		[ilog2(VM_EXEC)]	= "ex",

		[ilog2(VM_SHARED)]	= "sh",

		[ilog2(VM_MAYREAD)]	= "mr",

		[ilog2(VM_MAYWRITE)]	= "mw",

		[ilog2(VM_MAYEXEC)]	= "me",

		[ilog2(VM_MAYSHARE)]	= "ms",

		[ilog2(VM_GROWSDOWN)]	= "gd",

		[ilog2(VM_PFNMAP)]	= "pf",

		[ilog2(VM_DENYWRITE)]	= "dw",

		[ilog2(VM_LOCKED)]	= "lo",

		[ilog2(VM_IO)]		= "io",

		[ilog2(VM_SEQ_READ)]	= "sr",

		[ilog2(VM_RAND_READ)]	= "rr",

		[ilog2(VM_DONTCOPY)]	= "dc",

		[ilog2(VM_DONTEXPAND)]	= "de",

		[ilog2(VM_ACCOUNT)]	= "ac",

		[ilog2(VM_NORESERVE)]	= "nr",

		[ilog2(VM_HUGETLB)]	= "ht",

		[ilog2(VM_NONLINEAR)]	= "nl",

		[ilog2(VM_ARCH_1)]	= "ar",

		[ilog2(VM_DONTDUMP)]	= "dd",

		[ilog2(VM_MIXEDMAP)]	= "mm",

		[ilog2(VM_HUGEPAGE)]	= "hg",

		[ilog2(VM_NOHUGEPAGE)]	= "nh",

		[ilog2(VM_MERGEABLE)]	= "mg",

	};

	size_t i;



	seq_puts(m, "VmFlags: ");

	for (i = 0; i < BITS_PER_LONG; i++) {

		if (vma->vm_flags & (1UL << i)) {

			seq_printf(m, "%c%c ",

				   mnemonics[i][0], mnemonics[i][1]);

		}

	}

	seq_putc(m, '\n');

}



static int show_smap(struct seq_file *m, void *v, int is_pid)

{

	struct proc_maps_private *priv = m->private;
@@ -581,6 +632,8 @@ static int show_smap(struct seq_file *m, void *v, int is_pid) 
		seq_printf(m, "Nonlinear:      %8lu kB\n",

				mss.nonlinear >> 10);



	show_smap_vma_flags(m, vma);



	if (m->count < m->size)  /* vma is copied successfully */

		m->version = (vma != get_gate_vma(task->mm))

			? vma->vm_start : 0;

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