kernel/linux.git/fs/afs/dynroot.c, branch v6.19.11

Merge tag 'vfs-6.19-rc1.inode' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-01T17:02:34+00:00

Pull vfs inode updates from Christian Brauner: "Features: - Hide inode->i_state behind accessors. Open-coded accesses prevent asserting they are done correctly. One obvious aspect is locking, but significantly more can be checked. For example it can be detected when the code is clearing flags which are already missing, or is setting flags when it is illegal (e.g., I_FREEING when ->i_count > 0) - Provide accessors for ->i_state, converts all filesystems using coccinelle and manual conversions (btrfs, ceph, smb, f2fs, gfs2, overlayfs, nilfs2, xfs), and makes plain ->i_state access fail to compile - Rework I_NEW handling to operate without fences, simplifying the code after the accessor infrastructure is in place Cleanups: - Move wait_on_inode() from writeback.h to fs.h - Spell out fenced ->i_state accesses with explicit smp_wmb/smp_rmb for clarity - Cosmetic fixes to LRU handling - Push list presence check into inode_io_list_del() - Touch up predicts in __d_lookup_rcu() - ocfs2: retire ocfs2_drop_inode() and I_WILL_FREE usage - Assert on ->i_count in iput_final() - Assert ->i_lock held in __iget() Fixes: - Add missing fences to I_NEW handling" * tag 'vfs-6.19-rc1.inode' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (22 commits) dcache: touch up predicts in __d_lookup_rcu() fs: push list presence check into inode_io_list_del() fs: cosmetic fixes to lru handling fs: rework I_NEW handling to operate without fences fs: make plain ->i_state access fail to compile xfs: use the new ->i_state accessors nilfs2: use the new ->i_state accessors overlayfs: use the new ->i_state accessors gfs2: use the new ->i_state accessors f2fs: use the new ->i_state accessors smb: use the new ->i_state accessors ceph: use the new ->i_state accessors btrfs: use the new ->i_state accessors Manual conversion to use ->i_state accessors of all places not covered by coccinelle Coccinelle-based conversion to use ->i_state accessors fs: provide accessors for ->i_state fs: spell out fenced ->i_state accesses with explicit smp_wmb/smp_rmb fs: move wait_on_inode() from writeback.h to fs.h fs: add missing fences to I_NEW handling ocfs2: retire ocfs2_drop_inode() and I_WILL_FREE usage ...

afs: Fix dynamic lookup to fail on cell lookup failure

2025-10-29T12:51:38+00:00

When a process tries to access an entry in /afs, normally what happens is that an automount dentry is created by ->lookup() and then triggered, which jumps through the ->d_automount() op. Currently, afs_dynroot_lookup() does not do cell DNS lookup, leaving that to afs_d_automount() to perform - however, it is possible to use access() or stat() on the automount point, which will always return successfully, have briefly created an afs_cell record if one did not already exist. This means that something like: test -d "/afs/.west" && echo Directory exists will print "Directory exists" even though no such cell is configured. This breaks the "west" python module available on PIP as it expects this access to fail. Now, it could be possible to make afs_dynroot_lookup() perform the DNS[*] lookup, but that would make "ls --color /afs" do this for each cell in /afs that is listed but not yet probed. kafs-client, probably wrongly, preloads the entire cell database and all the known cells are then listed in /afs - and doing ls /afs would be very, very slow, especially if any cell supplied addresses but was wholly inaccessible. [*] When I say "DNS", actually read getaddrinfo(), which could use any one of a host of mechanisms. Could also use static configuration. To fix this, make the following changes: (1) Create an enum to specify the origination point of a call to afs_lookup_cell() and pass this value into that function in place of the "excl" parameter (which can be derived from it). There are six points of origination: - Cell preload through /proc/net/afs/cells - Root cell config through /proc/net/afs/rootcell - Lookup in dynamic root - Automount trigger - Direct mount with mount() syscall - Alias check where YFS tells us the cell name is different (2) Add an extra state into the afs_cell state machine to indicate a cell that's been initialised, but not yet looked up. This is separate from one that can be considered active and has been looked up at least once. (3) Make afs_lookup_cell() vary its behaviour more, depending on where it was called from: If called from preload or root cell config, DNS lookup will not happen until we definitely want to use the cell (dynroot mount, automount, direct mount or alias check). The cell will appear in /afs but stat() won't trigger DNS lookup. If the cell already exists, dynroot will not wait for the DNS lookup to complete. If the cell did not already exist, dynroot will wait. If called from automount, direct mount or alias check, it will wait for the DNS lookup to complete. (4) Make afs_lookup_cell() return an error if lookup failed in one way or another. We try to return -ENOENT if the DNS says the cell does not exist and -EDESTADDRREQ if we couldn't access the DNS. Reported-by: Markus Suvanto Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220685 Signed-off-by: David Howells Link: https://patch.msgid.link/1784747.1761158912@warthog.procyon.org.uk Fixes: 1d0b929fc070 ("afs: Change dynroot to create contents on demand") Tested-by: Markus Suvanto cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Christian Brauner

Coccinelle-based conversion to use ->i_state accessors

2025-10-20T18:22:26+00:00

All places were patched by coccinelle with the default expecting that ->i_lock is held, afterwards entries got fixed up by hand to use unlocked variants as needed. The script: @@ expression inode, flags; @@ - inode->i_state & flags + inode_state_read(inode) & flags @@ expression inode, flags; @@ - inode->i_state &= ~flags + inode_state_clear(inode, flags) @@ expression inode, flag1, flag2; @@ - inode->i_state &= ~flag1 & ~flag2 + inode_state_clear(inode, flag1 | flag2) @@ expression inode, flags; @@ - inode->i_state |= flags + inode_state_set(inode, flags) @@ expression inode, flags; @@ - inode->i_state = flags + inode_state_assign(inode, flags) @@ expression inode, flags; @@ - flags = inode->i_state + flags = inode_state_read(inode) @@ expression inode, flags; @@ - READ_ONCE(inode->i_state) & flags + inode_state_read(inode) & flags Signed-off-by: Mateusz Guzik Signed-off-by: Christian Brauner

afs: Fix afs_dynroot_readdir() to not use the RCU read lock

2025-04-11T13:24:29+00:00

afs_dynroot_readdir() uses the RCU read lock to walk the cell list whilst emitting cell automount entries - but dir_emit() may write to a userspace buffer, thereby causing a fault to occur and waits to happen. Fix afs_dynroot_readdir() to get a shared lock on net->cells_lock instead. This can be triggered by enabling lockdep, preconfiguring a number of cells, doing "mount -t afs none /afs -o dyn" (or using the kafs-client package with afs.mount systemd unit enabled) and then doing "ls /afs". Fixes: 1d0b929fc070 ("afs: Change dynroot to create contents on demand") Reported-by: syzbot+3b6c5c6a1d0119b687a1@syzkaller.appspotmail.com Reported-by: syzbot+8245611446194a52150d@syzkaller.appspotmail.com Reported-by: syzbot+1aa62e6852a6ad1c7944@syzkaller.appspotmail.com Reported-by: syzbot+54e6c2176ba76c56217e@syzkaller.appspotmail.com Signed-off-by: David Howells Link: https://lore.kernel.org/1638014.1744145189@warthog.procyon.org.uk cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

Merge tag 'vfs-6.15-rc1.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-03-24T20:15:16+00:00

Pull vfs afs updates from Christian Brauner: "This contains the work for afs for this cycle: - Fix an occasional hang that's only really encountered when rmmod'ing the kafs module - Remove the "-o autocell" mount option. This is obsolete with the dynamic root and removing it makes the next patch slightly easier - Change how the dynamic root mount is constructed. Currently, the root directory is (de)populated when it is (un)mounted if there are cells already configured and, further, pairs of automount points have to be created/removed each time a cell is added/deleted This is changed so that readdir on the root dir lists all the known cell automount pairs plus the @cell symlinks and the inodes and dentries are constructed by lookup on demand. This simplifies the cell management code - A few improvements to the afs_volume and afs_server tracepoints - Pass trace info into the afs_lookup_cell() function to allow the trace log to indicate the purpose of the lookup - Remove the 'net' parameter from afs_unuse_cell() as it's superfluous - In rxrpc, allow a kernel app (such as kafs) to store a word of information on rxrpc_peer records - Use the information stored on the rxrpc_peer record to point to the afs_server record. This allows the server address lookup to be done away with - Simplify the afs_server ref/activity accounting to make each one self-contained and not garbage collected from the cell management work item - Simplify the afs_cell ref/activity accounting to make each one of these also self-contained and not driven by a central management work item The current code was intended to make it such that a single timer for the namespace and one work item per cell could do all the work required to maintain these records. This, however, made for some sequencing problems when cleaning up these records. Further, the attempt to pass refs along with timers and work items made getting it right rather tricky when the timer or work item already had a ref attached and now a ref had to be got rid of" * tag 'vfs-6.15-rc1.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: afs: Simplify cell record handling afs: Fix afs_server ref accounting afs: Use the per-peer app data provided by rxrpc rxrpc: Allow the app to store private data on peer structs afs: Drop the net parameter from afs_unuse_cell() afs: Make afs_lookup_cell() take a trace note afs: Improve server refcount/active count tracing afs: Improve afs_volume tracing to display a debug ID afs: Change dynroot to create contents on demand afs: Remove the "autocell" mount option

afs: Fix afs_atcell_get_link() to check if ws_cell is unset first

2025-03-19T08:23:05+00:00

Fix afs_atcell_get_link() to check if the workstation cell is unset before doing the RCU pathwalk bit where we dereference that. Fixes: 823869e1e616 ("afs: Fix afs_atcell_get_link() to handle RCU pathwalk") Reported-by: syzbot+76a6f18e3af82e84f264@syzkaller.appspotmail.com Signed-off-by: David Howells Link: https://lore.kernel.org/r/2481796.1742296819@warthog.procyon.org.uk Tested-by: syzbot+76a6f18e3af82e84f264@syzkaller.appspotmail.com cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

afs: Simplify cell record handling

2025-03-10T09:47:15+00:00

Simplify afs_cell record handling to avoid very occasional races that cause module removal to hang (it waits for all cell records to be removed). There are two things that particularly contribute to the difficulty: firstly, the code tries to pass a ref on the cell to the cell's maintenance work item (which gets awkward if the work item is already queued); and, secondly, there's an overall cell manager that tries to use just one timer for the entire cell collection (to avoid having loads of timers). However, both of these are probably unnecessarily restrictive. To simplify this, the following changes are made: (1) The cell record collection manager is removed. Each cell record manages itself individually. (2) Each afs_cell is given a second work item (cell->destroyer) that is queued when its refcount reaches zero. This is not done in the context of the putting thread as it might be in an inconvenient place to sleep. (3) Each afs_cell is given its own timer. The timer is used to expire the cell record after a period of unuse if not otherwise pinned and can also be used for other maintenance tasks if necessary (of which there are currently none as DNS refresh is triggered by filesystem operations). (4) The afs_cell manager work item (cell->manager) is no longer given a ref on the cell when queued; rather, the manager must be deleted. This does away with the need to deal with the consequences of losing a race to queue cell->manager. Clean up of extra queuing is deferred to the destroyer. (5) The cell destroyer work item makes sure the cell timer is removed and that the normal cell work is cancelled before farming the actual destruction off to RCU. (6) When a network namespace is destroyed or the kafs module is unloaded, it's now a simple matter of marking the namespace as dead then just waking up all the cell work items. They will then remove and destroy themselves once all remaining activity counts and/or a ref counts are dropped. This makes sure that all server records are dropped first. (7) The cell record state set is reduced to just four states: SETTING_UP, ACTIVE, REMOVING and DEAD. The record persists in the active state even when it's not being used until the time comes to remove it rather than downgrading it to an inactive state from whence it can be restored. This means that the cell still appears in /proc and /afs when not in use until it switches to the REMOVING state - at which point it is removed. Note that the REMOVING state is included so that someone wanting to resurrect the cell record is forced to wait whilst the cell is torn down in that state. Once it's in the DEAD state, it has been removed from net->cells tree and is no longer findable and can be replaced. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-16-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-12-dhowells@redhat.com/ # v4

afs: Drop the net parameter from afs_unuse_cell()

2025-03-10T09:47:15+00:00

Remove the redundant net parameter to afs_unuse_cell() as cell->net can be used instead. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-12-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-8-dhowells@redhat.com/ # v4

afs: Make afs_lookup_cell() take a trace note

2025-03-10T09:47:15+00:00

Pass a note to be added to the afs_cell tracepoint to afs_lookup_cell() so that different callers can be distinguished. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-11-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-7-dhowells@redhat.com/ # v4

afs: Change dynroot to create contents on demand

2025-03-10T09:47:15+00:00

Change the AFS dynamic root to do things differently: (1) Rather than having the creation of cell records create inodes and dentries for cell mountpoints, create them on demand during lookup. This simplifies cell management and locking as we no longer have to create these objects in advance *and* on speculative lookup by the user for a cell that isn't precreated. (2) Rather than using the libfs dentry-based readdir (the dentries now no longer exist until accessed from (1)), have readdir generate the contents by reading the list of cells. The @cell symlinks get pushed in positions 2 and 3 if rootcell has been configured. (3) Make the @cell symlink dentries persist for the life of the superblock or until reclaimed, but make cell mountpoints disappear immediately if unused. It's not perfect as someone doing an "ls -l /afs" may create a whole bunch of dentries which will be garbage collected immediately. But any dentry that gets automounted will be pinned by the mount, so it shouldn't be too bad. (4) Allocate the inode numbers for the cell mountpoints from an IDR to prevent duplicates appearing in the event it cycles round. The number allocated from the IDR is doubled to provide two inode numbers - one for the normal cell name (RO) and one for the dotted cell name (RW). Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-8-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-4-dhowells@redhat.com/ # v4