| Message ID | 20250319031545.2999807-4-neil@brown.name (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | tidy up various VFS lookup functions | expand |
On Wed, 2025-03-19 at 14:01 +1100, NeilBrown wrote: > From: NeilBrown <neilb@suse.de> > > cachefiles uses some VFS interfaces (such as vfs_mkdir) which take an > explicit mnt_idmap, and it passes &nop_mnt_idmap as cachefiles doesn't > yet support idmapped mounts. > > It also uses the lookup_one_len() family of functions which implicitly > use &nop_mnt_idmap. This mixture of implicit and explicit could be > confusing. When we eventually update cachefiles to support idmap mounts it Is that something we ever plan to do? > would be best if all places which need an idmap determined from the > mount point were similar and easily found. > > So this patch changes cachefiles to use lookup_one(), lookup_one_unlocked(), > and lookup_one_positive_unlocked(), passing &nop_mnt_idmap. > > This has the benefit of removing the remaining user of the > lookup_one_len functions where permission checking is actually needed. > Other callers don't care about permission checking and using these > function only where permission checking is needed is a valuable > simplification. > > This requires passing the name in a qstr. This is easily done with > QSTR() as the name is always nul terminated, and often strlen is used > anyway. ->d_name_len is removed as no longer useful. > > Signed-off-by: NeilBrown <neilb@suse.de> > --- > fs/cachefiles/internal.h | 1 - > fs/cachefiles/key.c | 1 - > fs/cachefiles/namei.c | 14 +++++++------- > 3 files changed, 7 insertions(+), 9 deletions(-) > > diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h > index 38c236e38cef..b62cd3e9a18e 100644 > --- a/fs/cachefiles/internal.h > +++ b/fs/cachefiles/internal.h > @@ -71,7 +71,6 @@ struct cachefiles_object { > int debug_id; > spinlock_t lock; > refcount_t ref; > - u8 d_name_len; /* Length of filename */ > enum cachefiles_content content_info:8; /* Info about content presence */ > unsigned long flags; > #define CACHEFILES_OBJECT_USING_TMPFILE 0 /* Have an unlinked tmpfile */ > diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c > index bf935e25bdbe..4927b533b9ae 100644 > --- a/fs/cachefiles/key.c > +++ b/fs/cachefiles/key.c > @@ -132,7 +132,6 @@ bool cachefiles_cook_key(struct cachefiles_object *object) > success: > name[len] = 0; > object->d_name = name; > - object->d_name_len = len; > _leave(" = %s", object->d_name); > return true; > } > diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c > index 83a60126de0f..4fc6f3efd3d9 100644 > --- a/fs/cachefiles/namei.c > +++ b/fs/cachefiles/namei.c > @@ -98,7 +98,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache, > retry: > ret = cachefiles_inject_read_error(); > if (ret == 0) > - subdir = lookup_one_len(dirname, dir, strlen(dirname)); > + subdir = lookup_one(&nop_mnt_idmap, QSTR(dirname), dir); > else > subdir = ERR_PTR(ret); > trace_cachefiles_lookup(NULL, dir, subdir); > @@ -337,7 +337,7 @@ int cachefiles_bury_object(struct cachefiles_cache *cache, > return -EIO; > } > > - grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer)); > + grave = lookup_one(&nop_mnt_idmap, QSTR(nbuffer), cache->graveyard); > if (IS_ERR(grave)) { > unlock_rename(cache->graveyard, dir); > trace_cachefiles_vfs_error(object, d_inode(cache->graveyard), > @@ -629,8 +629,8 @@ bool cachefiles_look_up_object(struct cachefiles_object *object) > /* Look up path "cache/vol/fanout/file". */ > ret = cachefiles_inject_read_error(); > if (ret == 0) > - dentry = lookup_positive_unlocked(object->d_name, fan, > - object->d_name_len); > + dentry = lookup_one_positive_unlocked(&nop_mnt_idmap, > + QSTR(object->d_name), fan); > else > dentry = ERR_PTR(ret); > trace_cachefiles_lookup(object, fan, dentry); > @@ -682,7 +682,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache, > inode_lock_nested(d_inode(fan), I_MUTEX_PARENT); > ret = cachefiles_inject_read_error(); > if (ret == 0) > - dentry = lookup_one_len(object->d_name, fan, object->d_name_len); > + dentry = lookup_one(&nop_mnt_idmap, QSTR(object->d_name), fan); > else > dentry = ERR_PTR(ret); > if (IS_ERR(dentry)) { > @@ -701,7 +701,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache, > dput(dentry); > ret = cachefiles_inject_read_error(); > if (ret == 0) > - dentry = lookup_one_len(object->d_name, fan, object->d_name_len); > + dentry = lookup_one(&nop_mnt_idmap, QSTR(object->d_name), fan); > else > dentry = ERR_PTR(ret); > if (IS_ERR(dentry)) { > @@ -750,7 +750,7 @@ static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache, > > inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); > > - victim = lookup_one_len(filename, dir, strlen(filename)); > + victim = lookup_one(&nop_mnt_idmap, QSTR(filename), dir); > if (IS_ERR(victim)) > goto lookup_error; > if (d_is_negative(victim)) Patch looks sane though. Reviewed-by: Jeff Layton <jlayton@kernel.org>
On Thu, Mar 20, 2025 at 06:22:08AM -0400, Jeff Layton wrote: > On Wed, 2025-03-19 at 14:01 +1100, NeilBrown wrote: > > From: NeilBrown <neilb@suse.de> > > > > cachefiles uses some VFS interfaces (such as vfs_mkdir) which take an > > explicit mnt_idmap, and it passes &nop_mnt_idmap as cachefiles doesn't > > yet support idmapped mounts. > > > > It also uses the lookup_one_len() family of functions which implicitly > > use &nop_mnt_idmap. This mixture of implicit and explicit could be > > confusing. When we eventually update cachefiles to support idmap mounts it > > Is that something we ever plan to do? It should be pretty easy to do. I just didn't see a reason to do it yet. Fwiw, the cache paths that cachefiles uses aren't private mounts like overlayfs does it, i.e., cachefiles doesn't do clone_private_mount() before stashing cache->mnt. That means properties of the mount can simply change beneath cachefilesd. And afaict cache->mnt isn't even opened for writing so the mount could suddenly go read-only behind cachefilesd's back. It probably will ignore that since it doesn't use mnt_want_write() apart for xattrs. > > > would be best if all places which need an idmap determined from the > > mount point were similar and easily found. > > > > So this patch changes cachefiles to use lookup_one(), lookup_one_unlocked(), > > and lookup_one_positive_unlocked(), passing &nop_mnt_idmap. > > > > This has the benefit of removing the remaining user of the > > lookup_one_len functions where permission checking is actually needed. > > Other callers don't care about permission checking and using these > > function only where permission checking is needed is a valuable > > simplification. > > > > This requires passing the name in a qstr. This is easily done with > > QSTR() as the name is always nul terminated, and often strlen is used > > anyway. ->d_name_len is removed as no longer useful. > > > > Signed-off-by: NeilBrown <neilb@suse.de> > > --- > > fs/cachefiles/internal.h | 1 - > > fs/cachefiles/key.c | 1 - > > fs/cachefiles/namei.c | 14 +++++++------- > > 3 files changed, 7 insertions(+), 9 deletions(-) > > > > diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h > > index 38c236e38cef..b62cd3e9a18e 100644 > > --- a/fs/cachefiles/internal.h > > +++ b/fs/cachefiles/internal.h > > @@ -71,7 +71,6 @@ struct cachefiles_object { > > int debug_id; > > spinlock_t lock; > > refcount_t ref; > > - u8 d_name_len; /* Length of filename */ > > enum cachefiles_content content_info:8; /* Info about content presence */ > > unsigned long flags; > > #define CACHEFILES_OBJECT_USING_TMPFILE 0 /* Have an unlinked tmpfile */ > > diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c > > index bf935e25bdbe..4927b533b9ae 100644 > > --- a/fs/cachefiles/key.c > > +++ b/fs/cachefiles/key.c > > @@ -132,7 +132,6 @@ bool cachefiles_cook_key(struct cachefiles_object *object) > > success: > > name[len] = 0; > > object->d_name = name; > > - object->d_name_len = len; > > _leave(" = %s", object->d_name); > > return true; > > } > > diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c > > index 83a60126de0f..4fc6f3efd3d9 100644 > > --- a/fs/cachefiles/namei.c > > +++ b/fs/cachefiles/namei.c > > @@ -98,7 +98,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache, > > retry: > > ret = cachefiles_inject_read_error(); > > if (ret == 0) > > - subdir = lookup_one_len(dirname, dir, strlen(dirname)); > > + subdir = lookup_one(&nop_mnt_idmap, QSTR(dirname), dir); > > else > > subdir = ERR_PTR(ret); > > trace_cachefiles_lookup(NULL, dir, subdir); > > @@ -337,7 +337,7 @@ int cachefiles_bury_object(struct cachefiles_cache *cache, > > return -EIO; > > } > > > > - grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer)); > > + grave = lookup_one(&nop_mnt_idmap, QSTR(nbuffer), cache->graveyard); > > if (IS_ERR(grave)) { > > unlock_rename(cache->graveyard, dir); > > trace_cachefiles_vfs_error(object, d_inode(cache->graveyard), > > @@ -629,8 +629,8 @@ bool cachefiles_look_up_object(struct cachefiles_object *object) > > /* Look up path "cache/vol/fanout/file". */ > > ret = cachefiles_inject_read_error(); > > if (ret == 0) > > - dentry = lookup_positive_unlocked(object->d_name, fan, > > - object->d_name_len); > > + dentry = lookup_one_positive_unlocked(&nop_mnt_idmap, > > + QSTR(object->d_name), fan); > > else > > dentry = ERR_PTR(ret); > > trace_cachefiles_lookup(object, fan, dentry); > > @@ -682,7 +682,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache, > > inode_lock_nested(d_inode(fan), I_MUTEX_PARENT); > > ret = cachefiles_inject_read_error(); > > if (ret == 0) > > - dentry = lookup_one_len(object->d_name, fan, object->d_name_len); > > + dentry = lookup_one(&nop_mnt_idmap, QSTR(object->d_name), fan); > > else > > dentry = ERR_PTR(ret); > > if (IS_ERR(dentry)) { > > @@ -701,7 +701,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache, > > dput(dentry); > > ret = cachefiles_inject_read_error(); > > if (ret == 0) > > - dentry = lookup_one_len(object->d_name, fan, object->d_name_len); > > + dentry = lookup_one(&nop_mnt_idmap, QSTR(object->d_name), fan); > > else > > dentry = ERR_PTR(ret); > > if (IS_ERR(dentry)) { > > @@ -750,7 +750,7 @@ static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache, > > > > inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); > > > > - victim = lookup_one_len(filename, dir, strlen(filename)); > > + victim = lookup_one(&nop_mnt_idmap, QSTR(filename), dir); > > if (IS_ERR(victim)) > > goto lookup_error; > > if (d_is_negative(victim)) > > Patch looks sane though. > > Reviewed-by: Jeff Layton <jlayton@kernel.org>
Christian Brauner <brauner@kernel.org> wrote: > > > It also uses the lookup_one_len() family of functions which implicitly > > > use &nop_mnt_idmap. This mixture of implicit and explicit could be > > > confusing. When we eventually update cachefiles to support idmap mounts > > > it > > > > Is that something we ever plan to do? > > It should be pretty easy to do. I just didn't see a reason to do it yet. > > Fwiw, the cache paths that cachefiles uses aren't private mounts like > overlayfs does it, i.e., cachefiles doesn't do clone_private_mount() before > stashing cache->mnt. ... This is probably something cachefilesd needs to do in userspace before telling the kernel through /dev/cachefiles where to find the cache. David
On Thu, Mar 20, 2025 at 01:49:25PM +0000, David Howells wrote: > Christian Brauner <brauner@kernel.org> wrote: > > > > > It also uses the lookup_one_len() family of functions which implicitly > > > > use &nop_mnt_idmap. This mixture of implicit and explicit could be > > > > confusing. When we eventually update cachefiles to support idmap mounts > > > > it > > > > > > Is that something we ever plan to do? > > > > It should be pretty easy to do. I just didn't see a reason to do it yet. > > > > Fwiw, the cache paths that cachefiles uses aren't private mounts like > > overlayfs does it, i.e., cachefiles doesn't do clone_private_mount() before > > stashing cache->mnt. ... > > This is probably something cachefilesd needs to do in userspace before telling > the kernel through /dev/cachefiles where to find the cache. Afaict, I don't think it matters whether the mount is actually attached to a mount namespace so cachefilesd could just do: fd_tree = open_tree(AT_FDCWD, "/path/to/cache", AT_EMPTY_PATH | OPEN_TREE_CLONE); and use the detached mount for all cachefilesd interactions.
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h index 38c236e38cef..b62cd3e9a18e 100644 --- a/fs/cachefiles/internal.h +++ b/fs/cachefiles/internal.h @@ -71,7 +71,6 @@ struct cachefiles_object { int debug_id; spinlock_t lock; refcount_t ref; - u8 d_name_len; /* Length of filename */ enum cachefiles_content content_info:8; /* Info about content presence */ unsigned long flags; #define CACHEFILES_OBJECT_USING_TMPFILE 0 /* Have an unlinked tmpfile */ diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c index bf935e25bdbe..4927b533b9ae 100644 --- a/fs/cachefiles/key.c +++ b/fs/cachefiles/key.c @@ -132,7 +132,6 @@ bool cachefiles_cook_key(struct cachefiles_object *object) success: name[len] = 0; object->d_name = name; - object->d_name_len = len; _leave(" = %s", object->d_name); return true; } diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c index 83a60126de0f..4fc6f3efd3d9 100644 --- a/fs/cachefiles/namei.c +++ b/fs/cachefiles/namei.c @@ -98,7 +98,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache, retry: ret = cachefiles_inject_read_error(); if (ret == 0) - subdir = lookup_one_len(dirname, dir, strlen(dirname)); + subdir = lookup_one(&nop_mnt_idmap, QSTR(dirname), dir); else subdir = ERR_PTR(ret); trace_cachefiles_lookup(NULL, dir, subdir); @@ -337,7 +337,7 @@ int cachefiles_bury_object(struct cachefiles_cache *cache, return -EIO; } - grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer)); + grave = lookup_one(&nop_mnt_idmap, QSTR(nbuffer), cache->graveyard); if (IS_ERR(grave)) { unlock_rename(cache->graveyard, dir); trace_cachefiles_vfs_error(object, d_inode(cache->graveyard), @@ -629,8 +629,8 @@ bool cachefiles_look_up_object(struct cachefiles_object *object) /* Look up path "cache/vol/fanout/file". */ ret = cachefiles_inject_read_error(); if (ret == 0) - dentry = lookup_positive_unlocked(object->d_name, fan, - object->d_name_len); + dentry = lookup_one_positive_unlocked(&nop_mnt_idmap, + QSTR(object->d_name), fan); else dentry = ERR_PTR(ret); trace_cachefiles_lookup(object, fan, dentry); @@ -682,7 +682,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache, inode_lock_nested(d_inode(fan), I_MUTEX_PARENT); ret = cachefiles_inject_read_error(); if (ret == 0) - dentry = lookup_one_len(object->d_name, fan, object->d_name_len); + dentry = lookup_one(&nop_mnt_idmap, QSTR(object->d_name), fan); else dentry = ERR_PTR(ret); if (IS_ERR(dentry)) { @@ -701,7 +701,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache, dput(dentry); ret = cachefiles_inject_read_error(); if (ret == 0) - dentry = lookup_one_len(object->d_name, fan, object->d_name_len); + dentry = lookup_one(&nop_mnt_idmap, QSTR(object->d_name), fan); else dentry = ERR_PTR(ret); if (IS_ERR(dentry)) { @@ -750,7 +750,7 @@ static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache, inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); - victim = lookup_one_len(filename, dir, strlen(filename)); + victim = lookup_one(&nop_mnt_idmap, QSTR(filename), dir); if (IS_ERR(victim)) goto lookup_error; if (d_is_negative(victim))