John Baldwin 7077c42623 Add a new file operations hook for mmap operations. File type-specific ... logic is now placed in the mmap hook implementation rather than requiring it to be placed in sys/vm/vm_mmap.c. This hook allows new file types to support mmap() as well as potentially allowing mmap() for existing file types that do not currently support any mapping. The vm_mmap() function is now split up into two functions. A new vm_mmap_object() function handles the "back half" of vm_mmap() and accepts a referenced VM object to map rather than a (handle, handle_type) tuple. vm_mmap() is now reduced to converting a (handle, handle_type) tuple to a a VM object and then calling vm_mmap_object() to handle the actual mapping. The vm_mmap() function remains for use by other parts of the kernel (e.g. device drivers and exec) but now only supports mapping vnodes, character devices, and anonymous memory. The mmap() system call invokes vm_mmap_object() directly with a NULL object for anonymous mappings. For mappings using a file descriptor, the descriptors fo_mmap() hook is invoked instead. The fo_mmap() hook is responsible for performing type-specific checks and adjustments to arguments as well as possibly modifying mapping parameters such as flags or the object offset. The fo_mmap() hook routines then call vm_mmap_object() to handle the actual mapping. The fo_mmap() hook is optional. If it is not set, then fo_mmap() will fail with ENODEV. A fo_mmap() hook is implemented for regular files, character devices, and shared memory objects (created via shm_open()). While here, consistently use the VM_PROT_* constants for the vm_prot_t type for the 'prot' variable passed to vm_mmap() and vm_mmap_object() as well as the vm_mmap_vnode() and vm_mmap_cdev() helper routines. Previously some places were using the mmap()-specific PROT_* constants instead. While this happens to work because PROT_xx == VM_PROT_xx, using VM_PROT_* is more correct. Differential Revision: https://reviews.freebsd.org/D2658 Reviewed by: alc (glanced over), kib MFC after: 1 month Sponsored by: Chelsio		2015-06-04 19:41:15 +00:00
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devfs_devs.c	Disable timestamping on devfs read/write operations by default.	2015-03-21 01:14:11 +00:00
devfs_dir.c
devfs_int.h	Stop enforcing additional reference on all cdevs, which was introduced	2015-01-19 17:36:52 +00:00
devfs_rule.c
devfs_vfsops.c
devfs_vnops.c	Add a new file operations hook for mmap operations. File type-specific	2015-06-04 19:41:15 +00:00
devfs.h