> And there is one more lowmem driver developed by Nokia for Nokia 8xx > tablets it seems. CCed Tony Lindgren, Juha and Viktor. > > http://git.kernel.org/?p=linux/kernel/git/tmlind/linux-omap-2.6.git;a=blob;f=security/lowmem.c;h=ae78a530af39703e335ad769f1e6f097f63ec6dd;hb=HEAD quick review. > 325 static struct security_operations lowmem_security_ops = { > 326 /* Use the capability functions for some of the hooks */ > 327 .ptrace_may_access = cap_ptrace_may_access, > 328 .ptrace_traceme = cap_ptrace_traceme, > 329 .capget = cap_capget, > 330 .capset_check = cap_capset_check, > 331 .capset_set = cap_capset_set, > 332 .capable = cap_capable, > 333 > 334 .bprm_apply_creds = cap_bprm_apply_creds, > 335 .bprm_set_security = cap_bprm_set_security, > 336 > 337 .task_post_setuid = cap_task_post_setuid, > 338 .task_reparent_to_init = cap_task_reparent_to_init, > 339 .vm_enough_memory = low_vm_enough_memory, > 340 }; .vm_enough_memory is the hook of virtual memory accounting, not rss. modern almost linux application and glibc largely use virtual address space than actual resident memory. then, vm_enough_memory don't provide proper hook. > 57 static ctl_table lowmem_table[] = { > 58 { > 59 .ctl_name = VM_LOWMEM_DENY_PAGES, > 60 .procname = "lowmem_deny_watermark_pages", > 61 .data = &deny_pages, > 62 .maxlen = sizeof(long), > 63 .mode = 0644, > 64 .child = NULL, > 65 .proc_handler = &proc_dointvec, > 66 .strategy = &sysctl_intvec, > 67 }, { you can set .ctl_name to CTL_UNNUMBERED. > 249 static int low_vm_enough_memory(struct mm_struct *mm, long pages) > 250 { > 251 unsigned long free, allowed; > 252 int cap_sys_admin = 0, notify; > 253 > 254 if (cap_capable(current, CAP_SYS_ADMIN) == 0) > 255 cap_sys_admin = 1; > 256 > 257 allowed = totalram_pages - hugetlb_total_pages(); > 258 allowed_pages = allowed; > 259 > 260 /* We activate ourselves only after both parameters have been > 261 * configured. */ > 262 if (deny_pages == 0 || notify_low_pages == 0 || notify_high_pages == 0) > 263 return __vm_enough_memory(mm, pages, cap_sys_admin); > 264 > 265 vm_acct_memory(pages); > 266 > 267 /* Easily freed pages when under VM pressure or direct reclaim */ > 268 free = global_page_state(NR_FILE_PAGES); this line assume file page can evictable. but it is not true. we should consider mlocked file page. > 269 free += nr_swap_pages; > 270 free += global_page_state(NR_SLAB_RECLAIMABLE); > 271 > 272 if (likely(free > notify_low_pages)) > 273 goto enough_memory; > 274 > 275 /* No luck, lets make it more expensive and try again.. */ > 276 free += nr_free_pages(); > 277 > 278 if (free < deny_pages) { > 279 int i; > 280 > 281 lowmem_free_pages = free; > 282 low_watermark_state(1); > 283 high_watermark_state(1); > 284 /* Memory allocations by root are always allowed */ > 285 if (cap_sys_admin) > 286 return 0; > 287 > 288 /* OOM unkillable process is allowed to consume memory */ > 289 if (current->oomkilladj == OOM_DISABLE) > 290 return 0; No generic assumption. > 292 /* uids from allowed_uids vector are also allowed no matter what */ > 293 for (i = 0; i < LOWMEM_MAX_UIDS && allowed_uids[i]; i++) > 294 if (current->uid == allowed_uids[i]) > 295 return 0; Oops, LOWMEM_MAX_UIDS is ugly restriction. > 297 vm_unacct_memory(pages); > 298 if (printk_ratelimit()) { > 299 printk(MY_NAME ": denying memory allocation to process %d (%s> )\n", > 300 current->pid, current->comm); > 301 } > 302 return -ENOMEM; > 303 } > 304 > 305 enough_memory: > 306 /* See if we need to notify level 1 */ > 307 low_watermark_state(free < notify_low_pages); > 308 > 309 /* > 310 * In the level 2 notification case things are more complicated, > 311 * as the level that we drop the state and send a notification > 312 * should be lower than when it is first triggered. Having this > 313 * on the same watermark level ends up bouncing back and forth > 314 * when applications are being stupid. > 315 */ > 316 notify = free < notify_high_pages; > 317 if (notify || free - nr_decay_pages > notify_high_pages) > 318 high_watermark_state(notify); > 319 > 320 /* We have plenty of memory */ > 321 lowmem_free_pages = free; It seems racy. if this code run on smp, lowmem_free_pages can hold unproper value. > 322 return 0; > 323 } then, In my first look, this code deeply depend on embedded and nokia process management policy. I don't think it can merge mainline. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
