* [PATCH AUTOSEL 5.10 23/56] fs: make unlazy_walk() error handling consistent
[not found] <20210224125212.482485-1-sashal@kernel.org>
@ 2021-02-24 12:51 ` Sasha Levin
2021-03-05 12:40 ` Pavel Machek
0 siblings, 1 reply; 2+ messages in thread
From: Sasha Levin @ 2021-02-24 12:51 UTC (permalink / raw)
To: linux-kernel, stable; +Cc: Jens Axboe, Al Viro, Sasha Levin, linux-fsdevel
From: Jens Axboe <axboe@kernel.dk>
[ Upstream commit e36cffed20a324e116f329a94061ae30dd26fb51 ]
Most callers check for non-zero return, and assume it's -ECHILD (which
it always will be). One caller uses the actual error return. Clean this
up and make it fully consistent, by having unlazy_walk() return a bool
instead. Rename it to try_to_unlazy() and return true on success, and
failure on error. That's easier to read.
No functional changes in this patch.
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: Sasha Levin <sashal@kernel.org>
---
fs/namei.c | 43 +++++++++++++++++--------------------------
1 file changed, 17 insertions(+), 26 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index d4a6dd7723038..7af66d5a0c1bf 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -669,17 +669,17 @@ static bool legitimize_root(struct nameidata *nd)
*/
/**
- * unlazy_walk - try to switch to ref-walk mode.
+ * try_to_unlazy - try to switch to ref-walk mode.
* @nd: nameidata pathwalk data
- * Returns: 0 on success, -ECHILD on failure
+ * Returns: true on success, false on failure
*
- * unlazy_walk attempts to legitimize the current nd->path and nd->root
+ * try_to_unlazy attempts to legitimize the current nd->path and nd->root
* for ref-walk mode.
* Must be called from rcu-walk context.
- * Nothing should touch nameidata between unlazy_walk() failure and
+ * Nothing should touch nameidata between try_to_unlazy() failure and
* terminate_walk().
*/
-static int unlazy_walk(struct nameidata *nd)
+static bool try_to_unlazy(struct nameidata *nd)
{
struct dentry *parent = nd->path.dentry;
@@ -694,14 +694,14 @@ static int unlazy_walk(struct nameidata *nd)
goto out;
rcu_read_unlock();
BUG_ON(nd->inode != parent->d_inode);
- return 0;
+ return true;
out1:
nd->path.mnt = NULL;
nd->path.dentry = NULL;
out:
rcu_read_unlock();
- return -ECHILD;
+ return false;
}
/**
@@ -792,7 +792,7 @@ static int complete_walk(struct nameidata *nd)
*/
if (!(nd->flags & (LOOKUP_ROOT | LOOKUP_IS_SCOPED)))
nd->root.mnt = NULL;
- if (unlikely(unlazy_walk(nd)))
+ if (!try_to_unlazy(nd))
return -ECHILD;
}
@@ -1466,7 +1466,7 @@ static struct dentry *lookup_fast(struct nameidata *nd,
unsigned seq;
dentry = __d_lookup_rcu(parent, &nd->last, &seq);
if (unlikely(!dentry)) {
- if (unlazy_walk(nd))
+ if (!try_to_unlazy(nd))
return ERR_PTR(-ECHILD);
return NULL;
}
@@ -1567,10 +1567,8 @@ static inline int may_lookup(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU) {
int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
- if (err != -ECHILD)
+ if (err != -ECHILD || !try_to_unlazy(nd))
return err;
- if (unlazy_walk(nd))
- return -ECHILD;
}
return inode_permission(nd->inode, MAY_EXEC);
}
@@ -1592,7 +1590,7 @@ static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq)
// unlazy even if we fail to grab the link - cleanup needs it
bool grabbed_link = legitimize_path(nd, link, seq);
- if (unlazy_walk(nd) != 0 || !grabbed_link)
+ if (!try_to_unlazy(nd) != 0 || !grabbed_link)
return -ECHILD;
if (nd_alloc_stack(nd))
@@ -1634,7 +1632,7 @@ static const char *pick_link(struct nameidata *nd, struct path *link,
touch_atime(&last->link);
cond_resched();
} else if (atime_needs_update(&last->link, inode)) {
- if (unlikely(unlazy_walk(nd)))
+ if (!try_to_unlazy(nd))
return ERR_PTR(-ECHILD);
touch_atime(&last->link);
}
@@ -1651,11 +1649,8 @@ static const char *pick_link(struct nameidata *nd, struct path *link,
get = inode->i_op->get_link;
if (nd->flags & LOOKUP_RCU) {
res = get(NULL, inode, &last->done);
- if (res == ERR_PTR(-ECHILD)) {
- if (unlikely(unlazy_walk(nd)))
- return ERR_PTR(-ECHILD);
+ if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
res = get(link->dentry, inode, &last->done);
- }
} else {
res = get(link->dentry, inode, &last->done);
}
@@ -2193,7 +2188,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
}
if (unlikely(!d_can_lookup(nd->path.dentry))) {
if (nd->flags & LOOKUP_RCU) {
- if (unlazy_walk(nd))
+ if (!try_to_unlazy(nd))
return -ECHILD;
}
return -ENOTDIR;
@@ -3127,7 +3122,6 @@ static const char *open_last_lookups(struct nameidata *nd,
struct inode *inode;
struct dentry *dentry;
const char *res;
- int error;
nd->flags |= op->intent;
@@ -3151,9 +3145,8 @@ static const char *open_last_lookups(struct nameidata *nd,
} else {
/* create side of things */
if (nd->flags & LOOKUP_RCU) {
- error = unlazy_walk(nd);
- if (unlikely(error))
- return ERR_PTR(error);
+ if (!try_to_unlazy(nd))
+ return ERR_PTR(-ECHILD);
}
audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
/* trailing slashes? */
@@ -3162,9 +3155,7 @@ static const char *open_last_lookups(struct nameidata *nd,
}
if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
- error = mnt_want_write(nd->path.mnt);
- if (!error)
- got_write = true;
+ got_write = !mnt_want_write(nd->path.mnt);
/*
* do _not_ fail yet - we might not need that or fail with
* a different error; let lookup_open() decide; we'll be
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH AUTOSEL 5.10 23/56] fs: make unlazy_walk() error handling consistent
2021-02-24 12:51 ` [PATCH AUTOSEL 5.10 23/56] fs: make unlazy_walk() error handling consistent Sasha Levin
@ 2021-03-05 12:40 ` Pavel Machek
0 siblings, 0 replies; 2+ messages in thread
From: Pavel Machek @ 2021-03-05 12:40 UTC (permalink / raw)
To: Sasha Levin; +Cc: linux-kernel, stable, Jens Axboe, Al Viro, linux-fsdevel
[-- Attachment #1: Type: text/plain, Size: 716 bytes --]
On Wed 2021-02-24 07:51:39, Sasha Levin wrote:
> From: Jens Axboe <axboe@kernel.dk>
>
> [ Upstream commit e36cffed20a324e116f329a94061ae30dd26fb51 ]
>
> Most callers check for non-zero return, and assume it's -ECHILD (which
> it always will be). One caller uses the actual error return. Clean this
> up and make it fully consistent, by having unlazy_walk() return a bool
> instead. Rename it to try_to_unlazy() and return true on success, and
> failure on error. That's easier to read.
>
> No functional changes in this patch.
Easier to read, but not fixing bug. I don't believe this is suitable
for stable.
Best regards,
Pavel
--
http://www.livejournal.com/~pavelmachek
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2021-02-24 12:51 ` [PATCH AUTOSEL 5.10 23/56] fs: make unlazy_walk() error handling consistent Sasha Levin
2021-03-05 12:40 ` Pavel Machek
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