)]}' { "commit": "8feae13110d60cc6287afabc2887366b0eb226c2", "tree": "b3188986faab70e753e00ea8670a11ba8ec844c0", "parents": [ "41836382ebb415d68d3ebc4525e78e871fe58baf" ], "author": { "name": "David Howells", "email": "dhowells@redhat.com", "time": "Thu Jan 08 12:04:47 2009 +0000" }, "committer": { "name": "David Howells", "email": "dhowells@redhat.com", "time": "Thu Jan 08 12:04:47 2009 +0000" }, "message": "NOMMU: Make VMAs per MM as for MMU-mode linux\n\nMake VMAs per mm_struct as for MMU-mode linux. This solves two problems:\n\n (1) In SYSV SHM where nattch for a segment does not reflect the number of\n shmat\u0027s (and forks) done.\n\n (2) In mmap() where the VMA\u0027s vm_mm is set to point to the parent mm by an\n exec\u0027ing process when VM_EXECUTABLE is specified, regardless of the fact\n that a VMA might be shared and already have its vm_mm assigned to another\n process or a dead process.\n\nA new struct (vm_region) is introduced to track a mapped region and to remember\nthe circumstances under which it may be shared and the vm_list_struct structure\nis discarded as it\u0027s no longer required.\n\nThis patch makes the following additional changes:\n\n (1) Regions are now allocated with alloc_pages() rather than kmalloc() and\n with no recourse to __GFP_COMP, so the pages are not composite. Instead,\n each page has a reference on it held by the region. Anything else that is\n interested in such a page will have to get a reference on it to retain it.\n When the pages are released due to unmapping, each page is passed to\n put_page() and will be freed when the page usage count reaches zero.\n\n (2) Excess pages are trimmed after an allocation as the allocation must be\n made as a power-of-2 quantity of pages.\n\n (3) VMAs are added to the parent MM\u0027s R/B tree and mmap lists. As an MM may\n end up with overlapping VMAs within the tree, the VMA struct address is\n appended to the sort key.\n\n (4) Non-anonymous VMAs are now added to the backing inode\u0027s prio list.\n\n (5) Holes may be punched in anonymous VMAs with munmap(), releasing parts of\n the backing region. The VMA and region structs will be split if\n necessary.\n\n (6) sys_shmdt() only releases one attachment to a SYSV IPC shared memory\n segment instead of all the attachments at that addresss. Multiple\n shmat()\u0027s return the same address under NOMMU-mode instead of different\n virtual addresses as under MMU-mode.\n\n (7) Core dumping for ELF-FDPIC requires fewer exceptions for NOMMU-mode.\n\n (8) /proc/maps is now the global list of mapped regions, and may list bits\n that aren\u0027t actually mapped anywhere.\n\n (9) /proc/meminfo gains a line (tagged \"MmapCopy\") that indicates the amount\n of RAM currently allocated by mmap to hold mappable regions that can\u0027t be\n mapped directly. These are copies of the backing device or file if not\n anonymous.\n\nThese changes make NOMMU mode more similar to MMU mode. The downside is that\nNOMMU mode requires some extra memory to track things over NOMMU without this\npatch (VMAs are no longer shared, and there are now region structs).\n\nSigned-off-by: David Howells \u003cdhowells@redhat.com\u003e\nTested-by: Mike Frysinger \u003cvapier.adi@gmail.com\u003e\nAcked-by: Paul Mundt \u003clethal@linux-sh.org\u003e\n", "tree_diff": [ { "type": "modify", "old_id": "7714f57caad5b4312e7289761c0561c68b822049", "old_mode": 33188, "old_path": "Documentation/nommu-mmap.txt", "new_id": "02b89dcf38ac599c1dcca687f1ba763912232017", "new_mode": 33188, "new_path": "Documentation/nommu-mmap.txt" }, { "type": "modify", "old_id": "53099d4ee4211d072741841a6513aebf74161a54", "old_mode": 33188, "old_path": "arch/arm/include/asm/mmu.h", "new_id": "b561584d04a18ef6c631d1e05d69f6ff4b22d194", "new_mode": 33188, "new_path": "arch/arm/include/asm/mmu.h" }, { "type": "modify", "old_id": "757e43906ed4b45b5b3bf410ecb24db3f946ef0b", "old_mode": 33188, "old_path": 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