From a02f76c34d7d6d30b63ac64a8b34dea68593e8da Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 23 Feb 2008 15:14:28 +0000 Subject: [PATCH] get stack footprint of pathname resolution back to relative sanity Somebody had put struct nameidata in stack frame of link_path_walk(). Unfortunately, there are certain realities to deal with: * It's in the middle of recursion. Depth is equal to the nesting depth of symlinks, i.e. up to 8. * struct namiedata is, even if one discards the intent junk, at least 12 pointers + 5 ints. * moreover, adding a stack frame is not free in that situation. * there are fs methods called on top of that, and they also have stack footprint. * kernel stack is not infinite. The thing is, even if one chooses to deal with -ESTALE that way (and it's one hell of an overkill), the only thing that needs to be preserved is vfsmount + dentry, not the entire struct nameidata. Signed-off-by: Al Viro --- fs/namei.c | 63 +++++++++++++++++++++++++++++++------------------------------- 1 file changed, 32 insertions(+), 31 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 941c8e8228c0..7346e99d9283 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -106,7 +106,7 @@ * any extra contention... */ -static int link_path_walk(const char *name, struct nameidata *nd); +static int __link_path_walk(const char *name, struct nameidata *nd); /* In order to reduce some races, while at the same time doing additional * checking and hopefully speeding things up, we copy filenames to the @@ -563,6 +563,37 @@ walk_init_root(const char *name, struct nameidata *nd) return 1; } +/* + * Wrapper to retry pathname resolution whenever the underlying + * file system returns an ESTALE. + * + * Retry the whole path once, forcing real lookup requests + * instead of relying on the dcache. + */ +static __always_inline int link_path_walk(const char *name, struct nameidata *nd) +{ + struct path save = nd->path; + int result; + + /* make sure the stuff we saved doesn't go away */ + dget(save.dentry); + mntget(save.mnt); + + result = __link_path_walk(name, nd); + if (result == -ESTALE) { + /* nd->path had been dropped */ + nd->path = save; + dget(nd->path.dentry); + mntget(nd->path.mnt); + nd->flags |= LOOKUP_REVAL; + result = __link_path_walk(name, nd); + } + + path_put(&save); + + return result; +} + static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link) { int res = 0; @@ -1020,36 +1051,6 @@ return_err: return err; } -/* - * Wrapper to retry pathname resolution whenever the underlying - * file system returns an ESTALE. - * - * Retry the whole path once, forcing real lookup requests - * instead of relying on the dcache. - */ -static int link_path_walk(const char *name, struct nameidata *nd) -{ - struct nameidata save = *nd; - int result; - - /* make sure the stuff we saved doesn't go away */ - dget(save.path.dentry); - mntget(save.path.mnt); - - result = __link_path_walk(name, nd); - if (result == -ESTALE) { - *nd = save; - dget(nd->path.dentry); - mntget(nd->path.mnt); - nd->flags |= LOOKUP_REVAL; - result = __link_path_walk(name, nd); - } - - path_put(&save.path); - - return result; -} - static int path_walk(const char *name, struct nameidata *nd) { current->total_link_count = 0; -- cgit v1.2.2