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    Subject[PATCH v2 1/9] mm, debug: fix wrongly filtered flags in dump_vma()
    Date
    The dump_vma() function uses dump_flags() for printing the flags as symbolic
    names. That function however does a page-flags specific filtering of bits
    higher than NR_PAGEFLAGS in order to remove the zone id part. For dump_vma()
    this results in removing several VM_* flags from the symbolic translation.

    Fix this by refactoring dump_flags() to dump_flag_names(), which only prints
    the symbolic names in parentheses. Printing the raw flag value with a prefix,
    and any filtering is left to the caller. In addition to fixing the bug, this
    allows better flexibility, which will be useful to print gfp_flags by a later
    patch.

    Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
    ---
    mm/debug.c | 32 ++++++++++++++++++++------------
    1 file changed, 20 insertions(+), 12 deletions(-)

    diff --git a/mm/debug.c b/mm/debug.c
    index 8362765..d9718fc 100644
    --- a/mm/debug.c
    +++ b/mm/debug.c
    @@ -46,17 +46,14 @@ static const struct trace_print_flags pageflag_names[] = {
    #endif
    };

    -static void dump_flags(unsigned long flags,
    +static void dump_flag_names(unsigned long flags,
    const struct trace_print_flags *names, int count)
    {
    const char *delim = "";
    unsigned long mask;
    int i;

    - pr_emerg("flags: %#lx(", flags);
    -
    - /* remove zone id */
    - flags &= (1UL << NR_PAGEFLAGS) - 1;
    + pr_cont("(");

    for (i = 0; i < count && flags; i++) {

    @@ -79,6 +76,8 @@ static void dump_flags(unsigned long flags,
    void dump_page_badflags(struct page *page, const char *reason,
    unsigned long badflags)
    {
    + unsigned long printflags = page->flags;
    +
    pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",
    page, atomic_read(&page->_count), page_mapcount(page),
    page->mapping, page->index);
    @@ -86,13 +85,19 @@ void dump_page_badflags(struct page *page, const char *reason,
    pr_cont(" compound_mapcount: %d", compound_mapcount(page));
    pr_cont("\n");
    BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS);
    - dump_flags(page->flags, pageflag_names, ARRAY_SIZE(pageflag_names));
    +
    + pr_emerg("flags: %#lx", printflags);
    + /* remove zone id */
    + printflags &= (1UL << NR_PAGEFLAGS) - 1;
    + dump_flag_names(printflags, pageflag_names, ARRAY_SIZE(pageflag_names));
    +
    if (reason)
    pr_alert("page dumped because: %s\n", reason);
    if (page->flags & badflags) {
    - pr_alert("bad because of flags:\n");
    - dump_flags(page->flags & badflags,
    - pageflag_names, ARRAY_SIZE(pageflag_names));
    + printflags = page->flags & badflags;
    + pr_alert("bad because of flags: %#lx:", printflags);
    + dump_flag_names(printflags, pageflag_names,
    + ARRAY_SIZE(pageflag_names));
    }
    #ifdef CONFIG_MEMCG
    if (page->mem_cgroup)
    @@ -162,7 +167,9 @@ void dump_vma(const struct vm_area_struct *vma)
    (unsigned long)pgprot_val(vma->vm_page_prot),
    vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
    vma->vm_file, vma->vm_private_data);
    - dump_flags(vma->vm_flags, vmaflags_names, ARRAY_SIZE(vmaflags_names));
    + pr_emerg("flags: %#lx", vma->vm_flags);
    + dump_flag_names(vma->vm_flags, vmaflags_names,
    + ARRAY_SIZE(vmaflags_names));
    }
    EXPORT_SYMBOL(dump_vma);

    @@ -233,8 +240,9 @@ void dump_mm(const struct mm_struct *mm)
    "" /* This is here to not have a comma! */
    );

    - dump_flags(mm->def_flags, vmaflags_names,
    - ARRAY_SIZE(vmaflags_names));
    + pr_emerg("def_flags: %#lx(", mm->def_flags);
    + dump_flag_names(mm->def_flags, vmaflags_names,
    + ARRAY_SIZE(vmaflags_names));
    }

    #endif /* CONFIG_DEBUG_VM */
    --
    2.6.3


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