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    SubjectRe: [patch 2/6] fs: no games with DCACHE_UNHASHED 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

    - 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 <>
    Cc: Al Viro <>
    Acked-by: "David S. Miller" <>
    Signed-off-by: Andrew Morton <>
    Signed-off-by: Linus Torvalds <>

    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 <>
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      Last update: 2009-10-15 09:53    [W:0.027 / U:39.280 seconds]
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