David Howells 642fb4d1f1 [PATCH] NOMMU: Provide shared-writable mmap support on ramfs ... The attached patch makes ramfs support shared-writable mmaps by: (1) Attempting to perform a contiguous block allocation to the requested size when truncate attempts to increase the file from zero size, such as happens when: fd = shm_open("/file/on/ramfs", ...): ftruncate(fd, size_requested); addr = mmap(NULL, subsize, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED, fd, offset); (2) Permitting any shared-writable mapping over any contiguous set of extant pages. get_unmapped_area() will return the address into the actual ramfs pages. The mapping may start anywhere and be of any size, but may not go over the end of file. Multiple mappings may overlap in any way. (3) Not permitting a file to be shrunk if it would truncate any shared mappings (private mappings are copied). Thus this patch provides support for POSIX shared memory on NOMMU kernels, with certain limitations such as there being a large enough block of pages available to support the allocation and it only working on directly mappable filesystems. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>		2006-01-06 08:33:32 -08:00
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file-mmu.c	[PATCH] NOMMU: Provide shared-writable mmap support on ramfs	2006-01-06 08:33:32 -08:00
file-nommu.c	[PATCH] NOMMU: Provide shared-writable mmap support on ramfs	2006-01-06 08:33:32 -08:00
inode.c	[PATCH] NOMMU: Provide shared-writable mmap support on ramfs	2006-01-06 08:33:32 -08:00
internal.h	[PATCH] NOMMU: Provide shared-writable mmap support on ramfs	2006-01-06 08:33:32 -08:00
Makefile	[PATCH] NOMMU: Provide shared-writable mmap support on ramfs	2006-01-06 08:33:32 -08:00