From: Jens Axboe axboe@kernel.dk
stable inclusion from stable-v5.10.162 commit c1fe7bd3e1aa85865396b464b31f28b094a4353c category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6BTWC
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v...
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[ Upstream commit 6c6ec2b0a3e0381d886d531bd1471dfdb1509237 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Conflict: fs/namei.c
Signed-off-by: Li Lingfeng lilingfeng3@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Reviewed-by: Wang Weiyang wangweiyang2@huawei.com Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- fs/namei.c | 9 +++++++++ include/linux/namei.h | 1 + 2 files changed, 10 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c index 07c00ade4c1a..98e24fdb22c1 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -691,6 +691,8 @@ 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))) @@ -727,6 +729,8 @@ static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned se 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))) @@ -798,6 +802,7 @@ static int complete_walk(struct nameidata *nd) if (!(nd->state & ND_ROOT_PRESET)) if (!(nd->flags & LOOKUP_IS_SCOPED)) nd->root.mnt = NULL; + nd->flags &= ~LOOKUP_CACHED; if (!try_to_unlazy(nd)) return -ECHILD; } @@ -2210,6 +2215,10 @@ 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) diff --git a/include/linux/namei.h b/include/linux/namei.h index ca94eb5d2b16..be9a2b349ca7 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -43,6 +43,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT}; #define LOOKUP_NO_XDEV 0x040000 /* No mountpoint crossing. */ #define LOOKUP_BENEATH 0x080000 /* No escaping from starting point. */ #define LOOKUP_IN_ROOT 0x100000 /* Treat dirfd as fs root. */ +#define LOOKUP_CACHED 0x200000 /* Only do cached lookup */ /* LOOKUP_* flags which do scope-related checks based on the dirfd. */ #define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)