diff options
| author | Andrew Morton <akpm@osdl.org> | 2005-07-27 11:43:54 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-07-27 16:25:53 -0700 |
| commit | 1aaf18ff9de1f37bf674236fc0779c3aaa65b998 (patch) | |
| tree | 53df4d3dd0fbd81b79d5cdb63cf0d11853307a6b /mm/memory.c | |
| parent | 0cfc11ed45e4c00750039e5a18c0fc0d681e19db (diff) | |
[PATCH] check_user_page_readable() deadlock fix
Fix bug identifued by Richard Purdie <rpurdie@rpsys.net>.
oprofile calls check_user_page_readable() from interrupt context, so we
deadlock over various VFS locks.
But check_user_page_readable() doesn't imply either a read or a write of the
page's contents. Change __follow_page() so that check_user_page_readable()
can tell __follow_page() that we're not accessing the page's contents, and use
that info to avoid the troublesome lock-takings.
Also, make follow_page() inline for the single callsite in memory.c to save a
bit of stack space.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 25 |
1 files changed, 15 insertions, 10 deletions
diff --git a/mm/memory.c b/mm/memory.c index beabdefa6254..6fe77acbc1cd 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -776,8 +776,8 @@ unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address, * Do a quick page-table lookup for a single page. * mm->page_table_lock must be held. */ -static struct page * -__follow_page(struct mm_struct *mm, unsigned long address, int read, int write) +static struct page *__follow_page(struct mm_struct *mm, unsigned long address, + int read, int write, int accessed) { pgd_t *pgd; pud_t *pud; @@ -818,9 +818,11 @@ __follow_page(struct mm_struct *mm, unsigned long address, int read, int write) pfn = pte_pfn(pte); if (pfn_valid(pfn)) { page = pfn_to_page(pfn); - if (write && !pte_dirty(pte) && !PageDirty(page)) - set_page_dirty(page); - mark_page_accessed(page); + if (accessed) { + if (write && !pte_dirty(pte) &&!PageDirty(page)) + set_page_dirty(page); + mark_page_accessed(page); + } return page; } } @@ -829,16 +831,19 @@ out: return NULL; } -struct page * +inline struct page * follow_page(struct mm_struct *mm, unsigned long address, int write) { - return __follow_page(mm, address, /*read*/0, write); + return __follow_page(mm, address, 0, write, 1); } -int -check_user_page_readable(struct mm_struct *mm, unsigned long address) +/* + * check_user_page_readable() can be called frm niterrupt context by oprofile, + * so we need to avoid taking any non-irq-safe locks + */ +int check_user_page_readable(struct mm_struct *mm, unsigned long address) { - return __follow_page(mm, address, /*read*/1, /*write*/0) != NULL; + return __follow_page(mm, address, 1, 0, 0) != NULL; } EXPORT_SYMBOL(check_user_page_readable); |