On Wed, Aug 07, 2024 at 08:10:27AM -0400, Jeff Layton wrote: > Today, when opening a file we'll typically do a fast lookup, but if > O_CREAT is set, the kernel always takes the exclusive inode lock. I > assume this was done with the expectation that O_CREAT means that we > always expect to do the create, but that's often not the case. Many > programs set O_CREAT even in scenarios where the file already exists. > > This patch rearranges the pathwalk-for-open code to also attempt a > fast_lookup in certain O_CREAT cases. If a positive dentry is found, the > inode_lock can be avoided altogether, and if auditing isn't enabled, it > can stay in rcuwalk mode for the last step_into. > > One notable exception that is hopefully temporary: if we're doing an > rcuwalk and auditing is enabled, skip the lookup_fast. Legitimizing the > dentry in that case is more expensive than taking the i_rwsem for now. > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Thanks, Josef
