diff options
| author |   Jens Axboe <axboe@kernel.dk> | 2020-12-17 09:19:09 -0700 |
|---|---|---|
| committer |   Al Viro <viro@zeniv.linux.org.uk> | 2021-01-04 11:42:21 -0500 |
| commit | 6c6ec2b0a3e0381d886d531bd1471dfdb1509237 (patch) | |
| tree | 87edec0a250e14b3929f970917f34547a316c850 /fs/namei.c | |
| parent | saner calling conventions for unlazy_child() (diff) | |
| download | linux-dev-6c6ec2b0a3e0381d886d531bd1471dfdb1509237.tar.xz linux-dev-6c6ec2b0a3e0381d886d531bd1471dfdb1509237.zip | |
fs: add support for LOOKUP_CACHED
io_uring always punts opens to async context, since there's no control
over whether the lookup blocks or not. Add LOOKUP_CACHED to support
just doing the fast RCU based lookups, which we know will not block. If
we can do a cached path resolution of the filename, then we don't have
to always punt lookups for a worker.
During path resolution, we always do LOOKUP_RCU first. If that fails and
we terminate LOOKUP_RCU, then fail a LOOKUP_CACHED attempt as well.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c index 2ee219497460..4cae88733a5c 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -686,6 +686,8 @@ static bool try_to_unlazy(struct nameidata *nd) BUG_ON(!(nd->flags & LOOKUP_RCU)); nd->flags &= ~LOOKUP_RCU; + if (nd->flags & LOOKUP_CACHED) + goto out1; if (unlikely(!legitimize_links(nd))) goto out1; if (unlikely(!legitimize_path(nd, &nd->path, nd->seq))) @@ -722,6 +724,8 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi BUG_ON(!(nd->flags & LOOKUP_RCU)); nd->flags &= ~LOOKUP_RCU; + if (nd->flags & LOOKUP_CACHED) + goto out2; if (unlikely(!legitimize_links(nd))) goto out2; if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq))) @@ -792,6 +796,7 @@ static int complete_walk(struct nameidata *nd) */ if (!(nd->flags & (LOOKUP_ROOT | LOOKUP_IS_SCOPED))) nd->root.mnt = NULL; + nd->flags &= ~LOOKUP_CACHED; if (!try_to_unlazy(nd)) return -ECHILD; } @@ -2204,6 +2209,10 @@ static const char *path_init(struct nameidata *nd, unsigned flags) int error; const char *s = nd->name->name; + /* LOOKUP_CACHED requires RCU, ask caller to retry */ + if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED) + return ERR_PTR(-EAGAIN); + if (!*s) flags &= ~LOOKUP_RCU; if (flags & LOOKUP_RCU) |