diff options
| -rw-r--r-- | include/linux/page-flags.h | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 547aac7696cd..d276a4e2f825 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h | |||
| @@ -48,8 +48,20 @@ | |||
| 48 | 48 | ||
| 49 | /* | 49 | /* |
| 50 | * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break | 50 | * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break |
| 51 | * locked- and dirty-page accounting. The top eight bits of page->flags are | 51 | * locked- and dirty-page accounting. |
| 52 | * used for page->zone, so putting flag bits there doesn't work. | 52 | * |
| 53 | * The page flags field is split into two parts, the main flags area | ||
| 54 | * which extends from the low bits upwards, and the fields area which | ||
| 55 | * extends from the high bits downwards. | ||
| 56 | * | ||
| 57 | * | FIELD | ... | FLAGS | | ||
| 58 | * N-1 ^ 0 | ||
| 59 | * (N-FLAGS_RESERVED) | ||
| 60 | * | ||
| 61 | * The fields area is reserved for fields mapping zone, node and SPARSEMEM | ||
| 62 | * section. The boundry between these two areas is defined by | ||
| 63 | * FLAGS_RESERVED which defines the width of the fields section | ||
| 64 | * (see linux/mmzone.h). New flags must _not_ overlap with this area. | ||
| 53 | */ | 65 | */ |
| 54 | #define PG_locked 0 /* Page is locked. Don't touch. */ | 66 | #define PG_locked 0 /* Page is locked. Don't touch. */ |
| 55 | #define PG_error 1 | 67 | #define PG_error 1 |