At 05:05 09/02/06, Andrew Morton wrote: >On Tue, 03 Feb 2009 17:04:40 +0900 >Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx> wrote: > >> I removed i_mutex from generic_file_llseek. >> I think that the reason of protecting lseek with i_mutex is just >> touching i_size atomically. >> >> So I introduce i_size_read here so i_mutex is no longer needed. >> >> Following patch removes i_mutex from generic_file_llseek, and deletes >> generic_file_llseek_nolock totally. >> >> Currently there is i_mutex contention not only around lseek, but also >fsync or write. >> So, I think we can mitigate i_mutex contention between fsync lseek and >write by >> removing i_mutex. > >Prior to this change, generic_file_llseek() modified file->f_pos >atomically with respect to other i_mutex holders. > >After this change, it doesn't. Hi Andrew. Even before this change is applied, file->f_pos access is not atomic. sys_read change f_pos value through file_pos_write without i_mutex. I think seqlock is needed to make f_pos access atomic. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
