kernel/linux.git/fs/cachefiles/interface.c, branch v6.19.11

VFS: introduce start_removing_dentry()

2025-11-14T12:15:57+00:00

start_removing_dentry() is similar to start_removing() but instead of providing a name for lookup, the target dentry is given. start_removing_dentry() checks that the dentry is still hashed and in the parent, and if so it locks and increases the refcount so that end_removing() can be used to finish the operation. This is used in cachefiles, overlayfs, smb/server, and apparmor. There will be other users including ecryptfs. As start_removing_dentry() takes an extra reference to the dentry (to be put by end_removing()), there is no need to explicitly take an extra reference to stop d_delete() from using dentry_unlink_inode() to negate the dentry - as in cachefiles_delete_object(), and ksmbd_vfs_unlink(). cachefiles_bury_object() now gets an extra ref to the victim, which is drops. As it includes the needed end_removing() calls, the caller doesn't need them. Reviewed-by: Amir Goldstein Reviewed-by: Namjae Jeon Reviewed-by: Jeff Layton Signed-off-by: NeilBrown Link: https://patch.msgid.link/20251113002050.676694-9-neilb@ownmail.net Signed-off-by: Christian Brauner

cachefiles: Fix NULL pointer dereference in object->file

2024-11-11T13:39:38+00:00

At present, the object->file has the NULL pointer dereference problem in ondemand-mode. The root cause is that the allocated fd and object->file lifetime are inconsistent, and the user-space invocation to anon_fd uses object->file. Following is the process that triggers the issue: [write fd] [umount] cachefiles_ondemand_fd_write_iter fscache_cookie_state_machine cachefiles_withdraw_cookie if (!file) return -ENOBUFS cachefiles_clean_up_object cachefiles_unmark_inode_in_use fput(object->file) object->file = NULL // file NULL pointer dereference! __cachefiles_write(..., file, ...) Fix this issue by add an additional reference count to the object->file before write/llseek, and decrement after it finished. Fixes: c8383054506c ("cachefiles: notify the user daemon when looking up cookie") Signed-off-by: Zizhi Wo Link: https://lore.kernel.org/r/20241107110649.3980193-5-wozizhi@huawei.com Reviewed-by: David Howells Signed-off-by: Christian Brauner

cachefiles: extract ondemand info field from cachefiles_object

2023-11-25T15:03:57+00:00

We'll introduce a @work_struct field for @object in subsequent patches, it will enlarge the size of @object. As the result of that, this commit extracts ondemand info field from @object. Signed-off-by: Jia Zhu Link: https://lore.kernel.org/r/20231120041422.75170-3-zhujia.zj@bytedance.com Reviewed-by: Jingbo Xu Reviewed-by: David Howells Signed-off-by: Christian Brauner

fs: port vfs_*() helpers to struct mnt_idmap

2023-01-18T16:51:45+00:00

Convert to struct mnt_idmap. Last cycle we merged the necessary infrastructure in 256c8aed2b42 ("fs: introduce dedicated idmap type for mounts"). This is just the conversion to struct mnt_idmap. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate namespaces that are relevant on the filesystem with namespaces that are relevent on the mount level. Especially for non-vfs developers without detailed knowledge in this area this can be a potential source for bugs. Once the conversion to struct mnt_idmap is done all helpers down to the really low-level helpers will take a struct mnt_idmap argument instead of two namespace arguments. This way it becomes impossible to conflate the two eliminating the possibility of any bugs. All of the vfs and all filesystems only operate on struct mnt_idmap. Acked-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft)

cachefiles: notify the user daemon when withdrawing cookie

2022-05-17T16:11:17+00:00

Notify the user daemon that cookie is going to be withdrawn, providing a hint that the associated anonymous fd can be closed. Be noted that this is only a hint. The user daemon may close the associated anonymous fd when receiving the CLOSE request, then it will receive another anonymous fd when the cookie gets looked up. Or it may ignore the CLOSE request, and keep writing data through the anonymous fd. However the next time the cookie gets looked up, the user daemon will still receive another new anonymous fd. Signed-off-by: Jeffle Xu Acked-by: David Howells Link: https://lore.kernel.org/r/20220425122143.56815-5-jefflexu@linux.alibaba.com Signed-off-by: Gao Xiang

cachefiles: Fix incorrect length to fallocate()

2022-03-03T19:35:21+00:00

When cachefiles_shorten_object() calls fallocate() to shape the cache file to match the DIO size, it passes the total file size it wants to achieve, not the amount of zeros that should be inserted. Since this is meant to preallocate that amount of storage for the file, it can cause the cache to fill up the disk and hit ENOSPC. Fix this by passing the length actually required to go from the current EOF to the desired EOF. Fixes: 7623ed6772de ("cachefiles: Implement cookie resize for truncate") Reported-by: Jeffle Xu Signed-off-by: David Howells Tested-by: Jeff Layton Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/164630854858.3665356.17419701804248490708.stgit@warthog.procyon.org.uk # v1 Signed-off-by: Linus Torvalds

cachefiles: Implement cookie resize for truncate

2022-01-07T13:42:50+00:00

Implement resizing an object, using truncate and/or fallocate to adjust the object. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819646631.215744.13819016478175576761.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906952877.143852.4140962906331914859.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967162168.1823006.5941985259926902274.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021560394.640689.9972155785508094960.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Implement begin and end I/O operation

2022-01-07T13:42:44+00:00

Implement the methods for beginning and ending an I/O operation. When called to begin an I/O operation, we are guaranteed that the cookie has reached a certain stage (we're called by fscache after it has done a suitable wait). If a file is available, we paste a ref over into the cache resources for the I/O routines to use. This means that the object can be invalidated whilst the I/O is ongoing without the need to synchronise as the file pointer in the object is replaced, but the file pointer in the cache resources is unaffected. Ending the operation just requires ditching any refs we have and dropping the access guarantee that fscache got for us on the cookie. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819645033.215744.2199344081658268312.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906951916.143852.9531384743995679857.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967161222.1823006.4461476204800357263.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021559030.640689.3684291785218094142.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Implement backing file wrangling

2022-01-07T13:42:40+00:00

Implement the wrangling of backing files, including the following pieces: (1) Lookup and creation of a file on disk, using a tmpfile if the file isn't yet present. The file is then opened, sized for DIO and the file handle is attached to the cachefiles_object struct. The inode is marked to indicate that it's in use by a kernel service. (2) Invalidation of an object, creating a tmpfile and switching the file pointer in the cachefiles object. (3) Committing a file to disk, including setting the coherency xattr on it and, if necessary, creating a hard link to it. Note that this would be a good place to use Omar Sandoval's vfs_link() with AT_LINK_REPLACE[1] as I may have to unlink an old file before I can link a tmpfile into place. (4) Withdrawal of open objects when a cache is being withdrawn or a cookie is relinquished. This involves committing or discarding the file. Changes ======= ver #2: - Fix logging of wrong error[1]. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/20211203094950.GA2480@kili/ [1] Link: https://lore.kernel.org/r/163819644097.215744.4505389616742411239.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906949512.143852.14222856795032602080.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967158526.1823006.17482695321424642675.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021557060.640689.16373541458119269871.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Implement object lifecycle funcs

2022-01-07T13:42:08+00:00

Implement allocate, get, see and put functions for the cachefiles_object struct. The members of the struct we're going to need are also added. Additionally, implement a lifecycle tracepoint. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819639457.215744.4600093239395728232.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906939569.143852.3594314410666551982.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967148857.1823006.6332962598220464364.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021547762.640689.8422781599594931000.stgit@warthog.procyon.org.uk/ # v4