On 8 May 2012 00:28, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > Nick Piggin <npiggin@xxxxxxxxx> writes: > >> On 25 April 2012 22:44, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: >>> From: Miklos Szeredi <mszeredi@xxxxxxx> >>> >>> Use helper variable instead of path->dentry->d_inode before complete_walk(). >>> This will allow this code to be used in RCU mode. >> >> What do you mean, allow it to be used? > > I mean allow the code to be shared between RCU and non-RCU mode. See > 10/16. > >> >>> >>> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx> >>> --- >>> fs/namei.c | 7 ++++--- >>> 1 files changed, 4 insertions(+), 3 deletions(-) >>> >>> diff --git a/fs/namei.c b/fs/namei.c >>> index 46d4bf6..f21ddb3 100644 >>> --- a/fs/namei.c >>> +++ b/fs/namei.c >>> @@ -2360,15 +2360,16 @@ static struct file *do_last(struct nameidata *nd, struct path *path, >>> if (error) >>> nd->flags |= LOOKUP_JUMPED; >>> >>> + inode = path->dentry->d_inode ; >>> error = -ENOENT; >>> - if (!path->dentry->d_inode) >>> + if (!inode) >>> goto exit_dput; >>> >>> - if (path->dentry->d_inode->i_op->follow_link) >>> + if (inode->i_op->follow_link) >>> return NULL; >>> >>> path_to_nameidata(path, nd); >>> - nd->inode = path->dentry->d_inode; >>> + nd->inode = inode; >>> /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ >>> error = complete_walk(nd); >>> if (error) >> >> In rcu-walk mode, dentry->d_inode should not be accessed at all, >> outside of the core lookup code that (should) have the correct >> barriers and sequence locks. >> >> That logic should not escape into here, so I'm just not sure what >> you're doing here. > > Right, dentry->d_inode is *not* going to be dereferenced in RCU mode. > In RCU mode it will jump to the place just after the "inode = > path->dentry->d_inode;" line. See patch 10/16. Hmm, OK, I admittedly didn't apply all patches and look at the result. I wonder if that's getting too hairy... I'm sure consolidation is worthwhile though. Perhaps comment or even a BUG_ON to ensure it is not in rcu-walk mode, at points where you load the inode? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
