Messages in this thread | | | Date | Thu, 15 Oct 2009 09:44:35 +0200 | From | Eric Dumazet <> | Subject | Re: [patch 2/6] fs: no games with DCACHE_UNHASHED |
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npiggin@suse.de 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@cosmosbay.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Acked-by: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@cosmosbay.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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