Rich Felker 63678c32e2 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 <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

2016-05-20 17:58:30 -07:00

..

file-mmu.c

make new_sync_{read,write}() static

2015-04-11 22:29:40 -04:00

file-nommu.c

tmpfs/ramfs: fix VM_MAYSHARE mappings for NOMMU

2016-05-20 17:58:30 -07:00

inode.c

mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros

2016-04-04 10:41:08 -07:00

internal.h

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Makefile

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