diff options
author | Eric Dumazet <dada1@cosmosbay.com> | 2006-12-06 20:38:45 -0800 |
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committer | Linus Torvalds <torvalds@woody.osdl.org> | 2006-12-07 08:39:41 -0800 |
commit | d18de5a2721f84ffd6a5d637915746ed47becc1c (patch) | |
tree | 85fa93f5a2003746792931463ed41b7a19cc8632 /fs | |
parent | 1c69d921ed9cc6593ad4f60c0f9951cb0d62b0b4 (diff) | |
download | linux-d18de5a2721f84ffd6a5d637915746ed47becc1c.tar.bz2 |
[PATCH] don't insert pipe dentries into dentry_hashtable.
We currently insert pipe 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
pipe code, so that dput() can just kill_it.
This patch, combined with (avoid RCU for never hashed dentries) reduced
time of { pipe(p); close(p[0]); close(p[1]);} on my UP machine (1.6GHz
Pentium-M) from 3.23 us to 2.86 us (But this patch does not depend on other
patches, only bench results)
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/pipe.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index b1626f269a34..ae36b89b1a37 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -830,7 +830,14 @@ void free_pipe_info(struct inode *inode) static struct vfsmount *pipe_mnt __read_mostly; static int pipefs_delete_dentry(struct dentry *dentry) { - return 1; + /* + * At creation time, we pretended this dentry was hashed + * (by clearing DCACHE_UNHASHED bit in d_flags) + * At delete time, we restore the truth : not hashed. + * (so that dput() can proceed correctly) + */ + dentry->d_flags |= DCACHE_UNHASHED; + return 0; } static struct dentry_operations pipefs_dentry_operations = { @@ -891,17 +898,22 @@ struct file *create_write_pipe(void) if (!inode) goto err_file; - sprintf(name, "[%lu]", inode->i_ino); + this.len = sprintf(name, "[%lu]", inode->i_ino); this.name = name; - this.len = strlen(name); - this.hash = inode->i_ino; /* will go */ + this.hash = 0; err = -ENOMEM; dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this); if (!dentry) goto err_inode; dentry->d_op = &pipefs_dentry_operations; - d_add(dentry, inode); + /* + * We dont want to publish this dentry into global dentry hash table. + * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED + * This permits a working /proc/$pid/fd/XXX on pipes + */ + dentry->d_flags &= ~DCACHE_UNHASHED; + d_instantiate(dentry, inode); f->f_vfsmnt = mntget(pipe_mnt); f->f_dentry = dentry; f->f_mapping = inode->i_mapping; |