| From: Andy Whitcroft <apw@canonical.com> |
| Subject: [PATCH] MMAP_EXTEND mode requires we extend in full system page increments |
| Date: Wed, 12 Mar 2014 11:58:31 +0100 |
| |
| When extending a mmap file we must ensure we extend by full system pages, |
| otherwise there is a risk (when the filesystem page size is smaller than |
| the system page size) that we will not allocate disk extents to store |
| the memory and it will be lost resulting in data loss. |
| |
| Signed-off-by: Andy Whitcroft <apw@canonical.com> |
| Signed-off-by: Cédric Le Goater <clg@fr.ibm.com> |
| |
| --- |
| env_file.c | 9 +++++++++ |
| 1 file changed, 9 insertions(+) |
| |
| --- a/src/env/env_file.c |
| +++ b/src/env/env_file.c |
| @@ -28,6 +28,15 @@ __db_file_extend(env, fhp, size) |
| int ret; |
| char buf; |
| |
| +#ifdef HAVE_MMAP_EXTEND |
| + /* |
| + * We have to ensure we extend a mmap'd segment a full memory page at |
| + * a time or risk the end of the page not having any filesystem blocks |
| + * associated resulting in the data loss. |
| + */ |
| + size = DB_ALIGN(size, getpagesize()) - 1; |
| +#endif |
| + |
| buf = '\0'; |
| /* |
| * Extend the file by writing the last page. If the region is >4Gb, |