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| author | Rich Felker <dalias@libc.org> | 2016-05-21 01:57:47 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-21 02:58:30 +0200 |
| commit | 63678c32e209bd165f33432bbed72b2954ce5ae4 (patch) | |
| tree | 8e94976dbe50b78ca23292fe9cf5d69c580e3170 /init/do_mounts.h | |
| parent | mm: enable RLIMIT_DATA by default with workaround for valgrind (diff) | |
| download | linux-63678c32e209bd165f33432bbed72b2954ce5ae4.tar.xz linux-63678c32e209bd165f33432bbed72b2954ce5ae4.zip | |
tmpfs/ramfs: fix VM_MAYSHARE mappings for NOMMU
The nommu do_mmap expects f_op->get_unmapped_area to either succeed or
return -ENOSYS for VM_MAYSHARE (e.g. private read-only) mappings.
Returning addr in the non-MAP_SHARED case was completely wrong, and only
happened to work because addr was 0. However, it prevented VM_MAYSHARE
mappings from sharing backing with the fs cache, and forced such
mappings (including shareable program text) to be copied whenever the
number of mappings transitioned from 0 to 1, impacting performance and
memory usage. Subsequent mappings beyond the first still correctly
shared memory with the first.
Instead, treat VM_MAYSHARE identically to VM_SHARED at the file ops level;
do_mmap already handles the semantic differences between them.
Signed-off-by: Rich Felker <dalias@libc.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Greg Ungerer <gerg@uclinux.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'init/do_mounts.h')
0 files changed, 0 insertions, 0 deletions