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Many struct inode_operations in the kernel can be "const". Marking them const
moves these to the .rodata section, which avoids false sharing with potential
dirty data. In addition it'll catch accidental writes at compile time to
these shared resources.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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As pointed out by Hugh, ramfs would also benefit from using the new
set_page_dirty aop method for memory backed file systems.
Signed-off-by: Ken Chen <kenchen@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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ramfs doesn't provide the .set_dirty_page a_op, and when the BLOCK layer is
not configured in, 'set_page_dirty' makes a call via a NULL pointer.
Signed-off-by: Dimitri Gorokhovik <dimitri.gorokhovik@free.fr>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Signed-off-by: Josef Sipek <jsipek@fsl.cs.sunysb.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch cleans up generic_file_*_read/write() interfaces. Christoph
Hellwig gave me the idea for this clean ups.
In a nutshell, all filesystems should set .aio_read/.aio_write methods and use
do_sync_read/ do_sync_write() as their .read/.write methods. This allows us
to cleanup all variants of generic_file_* routines.
Final available interfaces:
generic_file_aio_read() - read handler
generic_file_aio_write() - write handler
generic_file_aio_write_nolock() - no lock write handler
__generic_file_aio_write_nolock() - internal worker routine
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix execution through the FDPIC binfmt of programs stored on ramfs by
preventing the ramfs mmap() returning successfully on a private mapping of
a ramfs file. This causes NOMMU mmap to make a copy of the mapped portion
of the file and map that instead.
This could be improved by granting direct mapping access to read-only
private mappings for which the data is stored on a contiguous run of pages.
However, this is only likely to be the case if the file was extended with
truncate before being written.
ramfs is left to map the file directly for shared mappings so that SYSV IPC
and POSIX shared memory both still work.
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Same as with already do with the file operations: keep them in .rodata and
prevents people from doing runtime patching.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Steven French <sfrench@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This is a conversion to make the various file_operations structs in fs/
const. Basically a regexp job, with a few manual fixups
The goal is both to increase correctness (harder to accidentally write to
shared datastructures) and reducing the false sharing of cachelines with
things that get dirty in .data (while .rodata is nicely read only and thus
cache clean)
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Now that compound page handling is properly fixed in the VM, move nommu
over to using compound pages rather than rolling their own refcounting.
nommu vm page refcounting is broken anyway, but there is no need to have
divergent code in the core VM now, nor when it gets fixed.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: David Howells <dhowells@redhat.com>
(Needs testing, please).
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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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>
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