Thanks again Ravi, The IPC array I talked about is the structure ipc_ids ... which is used as shm_ids for shared memory regions, sem_ids for semaphores and msg_ids for messages. Hope we are going right here!!! Asmita from MAASK >From: Ravi <kravi26@yahoo.com> >To: MAASK Group <maask12345@hotmail.com>, kernelnewbies@nl.linux.org >Subject: Re: usage of vm_area_struct in shared memory >Date: Sat, 19 Oct 2002 15:15:26 -0700 (PDT) > > > > We are aware that the shared memory structure in the IPC array, > > has a pointer to the inode which has a cyclic link list of > > vm_area_structs of all processes that have attached to that shared > > region. Is this array (vm_next_share or vm_next_prev) really used > > apart from update_mmu_cache or vmtruncate_list?? > >The vm_next_share and vm_pprev_share pointers are not for shared >memory only. They are used to keep track of shared file mappings also. >And vmtruncate_list() is a _real_ use for them: if more than one >process >is mapping the same file and the file got modified (truncated in this >case) >some way of updating the vma's of all those processes is needed. > >BTW, I didn't get which IPC array you are refering to. > > > Also when and where are the shmem_file_operations like > > shmem_file_read, shmem_file_map, etc invoked?? Are they by any > > chance related to accessing the shared memory used in shmget, > > shmat??? Or shm_open, shm_link?? > > If you are using shmget(), shmat(), etc. shmem_file_opearations are >not used. sys_shmget() does get an inode from the shm filesystem, but >it replaces the file operations with shm_file_operations. >I guess anonymous mmaps (mmapping /dev/zero) and creating/using files >in >/dev/shm will use shmem_file_operations. > >Hope this helps, >Ravi. > >__________________________________________________ >Do you Yahoo!? >Y! Web Hosting - Let the expert host your web site >http://webhosting.yahoo.com/ >-- >Kernelnewbies: Help each other learn about the Linux kernel. >Archive: http://mail.nl.linux.org/kernelnewbies/ >FAQ: http://kernelnewbies.org/faq/ _________________________________________________________________ Unlimited Internet access for only $21.95/month. Try MSN! http://resourcecenter.msn.com/access/plans/2monthsfree.asp -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
