kernel/linux.git/fs/kernfs, branch v5.16

Merge 5.15-rc6 into driver-core-next

2021-10-18T07:43:37+00:00

We need the driver-core fixes in here as well. Signed-off-by: Greg Kroah-Hartman

fs/kernfs/symlink.c: replace S_IRWXUGO with 0777 on kernfs_create_link()

2021-10-05T14:21:16+00:00

If one ends up extending this line checkpatch will complain about the use of S_IRWXUGO suggesting it is not preferred and that 0777 should be used instead. Take the tip from checkpatch and do that change before we do our subsequent changes. This makes no functional changes. Signed-off-by: Luis Chamberlain Link: https://lore.kernel.org/r/20210927163805.808907-8-mcgrof@kernel.org Signed-off-by: Greg Kroah-Hartman

kernfs: don't create a negative dentry if inactive node exists

2021-10-04T08:27:18+00:00

It's been reported that doing stress test for module insertion and removal can result in an ENOENT from libkmod for a valid module. In kernfs_iop_lookup() a negative dentry is created if there's no kernfs node associated with the dentry or the node is inactive. But inactive kernfs nodes are meant to be invisible to the VFS and creating a negative dentry for these can have unexpected side effects when the node transitions to an active state. The point of creating negative dentries is to avoid the expensive alloc/free cycle that occurs if there are frequent lookups for kernfs attributes that don't exist. So kernfs nodes that are not yet active should not result in a negative dentry being created so when they transition to an active state VFS lookups can create an associated dentry is a natural way. It's also been reported that https://github.com/osandov/blktests.git test block/001 hangs during the test. It was suggested that recent changes to blktests might have caused it but applying this patch resolved the problem without change to blktests. Fixes: c7e7c04274b1 ("kernfs: use VFS negative dentry caching") Tested-by: Yi Zhang ACKed-by: Al Viro Signed-off-by: Ian Kent Link: https://lore.kernel.org/r/163330943316.19450.15056895533949392922.stgit@mickey.themaw.net Signed-off-by: Greg Kroah-Hartman

kernfs: also call kernfs_set_rev() for positive dentry

2021-09-28T16:18:15+00:00

A KMSAN warning is reported by Alexander Potapenko: BUG: KMSAN: uninit-value in kernfs_dop_revalidate+0x61f/0x840 fs/kernfs/dir.c:1053 kernfs_dop_revalidate+0x61f/0x840 fs/kernfs/dir.c:1053 d_revalidate fs/namei.c:854 lookup_dcache fs/namei.c:1522 __lookup_hash+0x3a6/0x590 fs/namei.c:1543 filename_create+0x312/0x7c0 fs/namei.c:3657 do_mkdirat+0x103/0x930 fs/namei.c:3900 __do_sys_mkdir fs/namei.c:3931 __se_sys_mkdir fs/namei.c:3929 __x64_sys_mkdir+0xda/0x120 fs/namei.c:3929 do_syscall_x64 arch/x86/entry/common.c:51 It seems a positive dentry in kernfs becomes a negative dentry directly through d_delete() in vfs_rmdir(). dentry->d_time is uninitialized when accessing it in kernfs_dop_revalidate(), because it is only initialized when created as negative dentry in kernfs_iop_lookup(). The problem can be reproduced by the following command: cd /sys/fs/cgroup/pids && mkdir hi && stat hi && rmdir hi && stat hi A simple fixes seems to be initializing d->d_time for positive dentry in kernfs_iop_lookup() as well. The downside is the negative dentry will be revalidated again after it becomes negative in d_delete(), because the revison of its parent must have been increased due to its removal. Alternative solution is implement .d_iput for kernfs, and assign d_time for the newly-generated negative dentry in it. But we may need to take kernfs_rwsem to protect again the concurrent kernfs_link_sibling() on the parent directory, it is a little over-killing. Now the simple fix is chosen. Link: https://marc.info/?l=linux-fsdevel&m=163249838610499 Fixes: c7e7c04274b1 ("kernfs: use VFS negative dentry caching") Reported-by: Alexander Potapenko Signed-off-by: Hou Tao Link: https://lore.kernel.org/r/20210928140750.1274441-1-houtao1@huawei.com Signed-off-by: Greg Kroah-Hartman

kernfs: dont call d_splice_alias() under kernfs node lock

2021-07-27T07:29:15+00:00

The call to d_splice_alias() in kernfs_iop_lookup() doesn't depend on any kernfs node so there's no reason to hold the kernfs node lock when calling it. Reviewed-by: Miklos Szeredi Signed-off-by: Ian Kent Link: https://lore.kernel.org/r/162642772000.63632.10672683419693513226.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman

kernfs: use i_lock to protect concurrent inode updates

2021-07-27T07:29:15+00:00

The inode operations .permission() and .getattr() use the kernfs node write lock but all that's needed is the read lock to protect against partial updates of these kernfs node fields which are all done under the write lock. And .permission() is called frequently during path walks and can cause quite a bit of contention between kernfs node operations and path walks when the number of concurrent walks is high. To change kernfs_iop_getattr() and kernfs_iop_permission() to take the rw sem read lock instead of the write lock an additional lock is needed to protect against multiple processes concurrently updating the inode attributes and link count in kernfs_refresh_inode(). The inode i_lock seems like the sensible thing to use to protect these inode attribute updates so use it in kernfs_refresh_inode(). The last hunk in the patch, applied to kernfs_fill_super(), is possibly not needed but taking the lock was present originally. I prefer to continue to take it to protect against a partial update of the source kernfs fields during the call to kernfs_refresh_inode() made by kernfs_get_inode(). Reviewed-by: Miklos Szeredi Signed-off-by: Ian Kent Link: https://lore.kernel.org/r/162642771474.63632.16295959115893904470.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman

kernfs: switch kernfs to use an rwsem

2021-07-27T07:29:15+00:00

The kernfs global lock restricts the ability to perform kernfs node lookup operations in parallel during path walks. Change the kernfs mutex to an rwsem so that, when opportunity arises, node searches can be done in parallel with path walk lookups. Reviewed-by: Miklos Szeredi Signed-off-by: Ian Kent Link: https://lore.kernel.org/r/162642770946.63632.2218304587223241374.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman

kernfs: use VFS negative dentry caching

2021-07-27T07:29:14+00:00

If there are many lookups for non-existent paths these negative lookups can lead to a lot of overhead during path walks. The VFS allows dentries to be created as negative and hashed, and caches them so they can be used to reduce the fairly high overhead alloc/free cycle that occurs during these lookups. Use the kernfs node parent revision to identify if a change has been made to the containing directory so that the negative dentry can be discarded and the lookup redone. Reviewed-by: Miklos Szeredi Signed-off-by: Ian Kent Link: https://lore.kernel.org/r/162642770420.63632.15791924970508867106.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman

kernfs: add a revision to identify directory node changes

2021-07-27T07:29:14+00:00

Add a revision counter to kernfs directory nodes so it can be used to detect if a directory node has changed during negative dentry revalidation. There's an assumption that sizeof(unsigned long) <= sizeof(pointer) on all architectures and as far as I know that assumption holds. So adding a revision counter to the struct kernfs_elem_dir variant of the kernfs_node type union won't increase the size of the kernfs_node struct. This is because struct kernfs_elem_dir is at least sizeof(pointer) smaller than the largest union variant. It's tempting to make the revision counter a u64 but that would increase the size of kernfs_node on archs where sizeof(pointer) is smaller than the revision counter. Reviewed-by: Miklos Szeredi Signed-off-by: Ian Kent Link: https://lore.kernel.org/r/162642769895.63632.8356662784964509867.stgit@web.messagingengine.com Signed-off-by: Greg Kroah-Hartman

Merge tag 'driver-core-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

2021-07-05T20:51:41+00:00

Pull driver core changes from Greg KH: "Here is the small set of driver core and debugfs updates for 5.14-rc1. Included in here are: - debugfs api cleanups (touched some drivers) - devres updates - tiny driver core updates and tweaks Nothing major in here at all, and all have been in linux-next for a while with no reported issues" * tag 'driver-core-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (27 commits) docs: ABI: testing: sysfs-firmware-memmap: add some memmap types. devres: Enable trace events devres: No need to call remove_nodes() when there none present devres: Use list_for_each_safe_from() in remove_nodes() devres: Make locking straight forward in release_nodes() kernfs: move revalidate to be near lookup drivers/base: Constify static attribute_group structs firmware_loader: remove unneeded 'comma' macro devcoredump: remove contact information driver core: Drop helper devm_platform_ioremap_resource_wc() component: Rename 'dev' to 'parent' component: Drop 'dev' argument to component_match_realloc() device property: Don't check for NULL twice in the loops driver core: auxiliary bus: Fix typo in the docs drivers/base/node.c: make CACHE_ATTR define static DEVICE_ATTR_RO debugfs: remove return value of debugfs_create_ulong() debugfs: remove return value of debugfs_create_bool() scsi: snic: debugfs: remove local storage of debugfs files b43: don't save dentries for debugfs b43legacy: don't save dentries for debugfs ...