On Thu, Oct 15, 2009 at 09:44:35AM +0200, Eric Dumazet wrote: > npiggin@xxxxxxx a écrit : > > (this is in -mm) > > > > Filesystems outside the regular namespace do not have to clear DCACHE_UNHASHED > > in order to have a working /proc/$pid/fd/XXX. Nothing in proc prevents the > > fd link from being used if its dentry is not in the hash. > > > > Also, it does not get put into the dcache hash if DCACHE_UNHASHED is clear; > > that depends on the filesystem calling d_add or d_rehash. > > > > So delete the misleading comments and needless code. > > > > This was added in commit 304e61e6fbadec586dfe002b535f169a04248e49 > > [PATCH] net: don't insert socket dentries into dentry_hashtable > > We currently insert socket dentries into the global dentry hashtable. This > is suboptimal because there is currently no way these entries can be used > for a lookup(). (/proc/xxx/fd/xxx uses a different mechanism). Inserting > them in dentry hashtable slows dcache lookups. > > To let __dpath() still work correctly (ie not adding a " (deleted)") after > dentry name, we do : > > - Right after d_alloc(), pretend they are hashed by clearing the > DCACHE_UNHASHED bit. > > - Call d_instantiate() instead of d_add() : dentry is not inserted in > hash table. > > __dpath() & friends work as intended during dentry lifetime. > > - At dismantle time, once dput() must clear the dentry, setting again > DCACHE_UNHASHED bit inside the custom d_delete() function provided by > socket code, so that dput() can just kill_it. > > Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Acked-by: "David S. Miller" <davem@xxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxx> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxx> > > > > Back in 2006, we had to perform this hack in order to not leak '(deleted)' in __d_path() > > if (!IS_ROOT(dentry) && d_unhashed(dentry) && > (prepend(&end, &buflen, " (deleted)", 10) != 0)) > goto Elong; > > In current kernel this part became : > > if (d_unlinked(dentry) && > (prepend(&end, &buflen, " (deleted)", 10) != 0)) > goto Elong; > > > So your cleanup seems good, thanks ! > > Acked-by: Eric Dumazet <dada1@xxxxxxxxxxxxx> Ahh, hmm d_unlinked() is exactly the same code. OK, so I think this shows why I'm an idiot. I didn't think about the __d_path output. Though the comments are still misleading, in my defence (and my test programs did not use any anoninode fds)... Now both sockets and pipes define a d_dname so they are OK, but anon_inodes does not. I think they should probably be made to just provide a d_dname anyway so we can have the familiar format of "pseudofs:[ino]" rather than "[pseudofs]" that we have now. That should make this patch work for anon_inodes.c as well. -- 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
