kernel/linux.git/fs/dcache.c, branch v5.10.257

vfs: Don't leak disconnected dentries on umount

2025-10-29T13:01:24+00:00

[ Upstream commit 56094ad3eaa21e6621396cc33811d8f72847a834 ] When user calls open_by_handle_at() on some inode that is not cached, we will create disconnected dentry for it. If such dentry is a directory, exportfs_decode_fh_raw() will then try to connect this dentry to the dentry tree through reconnect_path(). It may happen for various reasons (such as corrupted fs or race with rename) that the call to lookup_one_unlocked() in reconnect_one() will fail to find the dentry we are trying to reconnect and instead create a new dentry under the parent. Now this dentry will not be marked as disconnected although the parent still may well be disconnected (at least in case this inconsistency happened because the fs is corrupted and .. doesn't point to the real parent directory). This creates inconsistency in disconnected flags but AFAICS it was mostly harmless. At least until commit f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") which removed adding of most disconnected dentries to sb->s_anon list. Thus after this commit cleanup of disconnected dentries implicitely relies on the fact that dput() will immediately reclaim such dentries. However when some leaf dentry isn't marked as disconnected, as in the scenario described above, the reclaim doesn't happen and the dentries are "leaked". Memory reclaim can eventually reclaim them but otherwise they stay in memory and if umount comes first, we hit infamous "Busy inodes after unmount" bug. Make sure all dentries created under a disconnected parent are marked as disconnected as well. Reported-by: syzbot+1d79ebe5383fc016cf07@syzkaller.appspotmail.com Fixes: f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") CC: stable@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Christian Brauner [ relocated DCACHE_DISCONNECTED propagation from d_alloc_parallel() to d_alloc() ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fs: better handle deep ancestor chains in is_subdir()

2024-07-27T08:40:21+00:00

[ Upstream commit 391b59b045004d5b985d033263ccba3e941a7740 ] Jan reported that 'cd ..' may take a long time in deep directory hierarchies under a bind-mount. If concurrent renames happen it is possible to livelock in is_subdir() because it will keep retrying. Change is_subdir() from simply retrying over and over to retry once and then acquire the rename lock to handle deep ancestor chains better. The list of alternatives to this approach were less then pleasant. Change the scope of rcu lock to cover the whole walk while at it. A big thanks to Jan and Linus. Both Jan and Linus had proposed effectively the same thing just that one version ended up being slightly more elegant. Reported-by: Jan Kara Signed-off-by: Linus Torvalds Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

vfs: don't mod negative dentry count when on shrinker list

2024-07-18T11:05:45+00:00

[ Upstream commit aabfe57ebaa75841db47ea59091ec3c5a06d2f52 ] The nr_dentry_negative counter is intended to only account negative dentries that are present on the superblock LRU. Therefore, the LRU add, remove and isolate helpers modify the counter based on whether the dentry is negative, but the shrinker list related helpers do not modify the counter, and the paths that change a dentry between positive and negative only do so if DCACHE_LRU_LIST is set. The problem with this is that a dentry on a shrinker list still has DCACHE_LRU_LIST set to indicate ->d_lru is in use. The additional DCACHE_SHRINK_LIST flag denotes whether the dentry is on LRU or a shrink related list. Therefore if a relevant operation (i.e. unlink) occurs while a dentry is present on a shrinker list, and the associated codepath only checks for DCACHE_LRU_LIST, then it is technically possible to modify the negative dentry count for a dentry that is off the LRU. Since the shrinker list related helpers do not modify the negative dentry count (because non-LRU dentries should not be included in the count) when the dentry is ultimately removed from the shrinker list, this can cause the negative dentry count to become permanently inaccurate. This problem can be reproduced via a heavy file create/unlink vs. drop_caches workload. On an 80xcpu system, I start 80 tasks each running a 1k file create/delete loop, and one task spinning on drop_caches. After 10 minutes or so of runtime, the idle/clean cache negative dentry count increases from somewhere in the range of 5-10 entries to several hundred (and increasingly grows beyond nr_dentry_unused). Tweak the logic in the paths that turn a dentry negative or positive to filter out the case where the dentry is present on a shrink related list. This allows the above workload to maintain an accurate negative dentry count. Fixes: af0c9af1b3f6 ("fs/dcache: Track & report number of negative dentries") Signed-off-by: Brian Foster Link: https://lore.kernel.org/r/20240703121301.247680-1-bfoster@redhat.com Acked-by: Ian Kent Reviewed-by: Josef Bacik Reviewed-by: Waiman Long Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

fs/dcache: Re-use value stored to dentry->d_flags instead of re-reading

2024-07-18T11:05:45+00:00

[ Upstream commit 8bfb40be31ddea0cb4664b352e1797cfe6c91976 ] Currently, the __d_clear_type_and_inode() writes the value flags to dentry->d_flags, then immediately re-reads it in order to use it in a if statement. This re-read is useless because no other update to dentry->d_flags can occur at this point. This commit therefore re-use flags in the if statement instead of re-reading dentry->d_flags. Signed-off-by: linke li Link: https://lore.kernel.org/r/tencent_5E187BD0A61BA28605E85405F15228254D0A@qq.com Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Stable-dep-of: aabfe57ebaa7 ("vfs: don't mod negative dentry count when on shrinker list") Signed-off-by: Sasha Levin

fast_dput(): handle underflows gracefully

2024-02-23T07:42:10+00:00

[ Upstream commit 504e08cebe1d4e1efe25f915234f646e74a364a8 ] If refcount is less than 1, we should just warn, unlock dentry and return true, so that the caller doesn't try to do anything else. Taking care of that leaves the rest of "lockref_put_return() has failed" case equivalent to "decrement refcount and rejoin the normal slow path after the point where we grab ->d_lock". NOTE: lockref_put_return() is strictly a fastpath thing - unlike the rest of lockref primitives, it does not contain a fallback. Caller (and it looks like fast_dput() is the only legitimate one in the entire kernel) has to do that itself. Reasons for lockref_put_return() failures: * ->d_lock held by somebody * refcount <= 0 * ... or an architecture not supporting lockref use of cmpxchg - sparc, anything non-SMP, config with spinlock debugging... We could add a fallback, but it would be a clumsy API - we'd have to distinguish between: (1) refcount > 1 - decremented, lock not held on return (2) refcount < 1 - left alone, probably no sense to hold the lock (3) refcount is 1, no cmphxcg - decremented, lock held on return (4) refcount is 1, cmphxcg supported - decremented, lock *NOT* held on return. We want to return with no lock held in case (4); that's the whole point of that thing. We very much do not want to have the fallback in case (3) return without a lock, since the caller might have to retake it in that case. So it wouldn't be more convenient than doing the fallback in the caller and it would be very easy to screw up, especially since the test coverage would suck - no way to test (3) and (4) on the same kernel build. Reviewed-by: Christian Brauner Signed-off-by: Al Viro Signed-off-by: Sasha Levin

vfs: Use sequence counter with associated spinlock

2020-07-29T14:14:27+00:00

A sequence counter write side critical section must be protected by some form of locking to serialize writers. A plain seqcount_t does not contain the information of which lock must be held when entering a write side critical section. Use the new seqcount_spinlock_t data type, which allows to associate a spinlock with the sequence counter. This enables lockdep to verify that the spinlock used for writer serialization is held when the write side critical section is entered. If lockdep is disabled this lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by: Ahmed S. Darwish Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200720155530.1173732-19-a.darwish@linutronix.de

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

2020-06-03T23:27:18+00:00

Pull networking updates from David Miller: 1) Allow setting bluetooth L2CAP modes via socket option, from Luiz Augusto von Dentz. 2) Add GSO partial support to igc, from Sasha Neftin. 3) Several cleanups and improvements to r8169 from Heiner Kallweit. 4) Add IF_OPER_TESTING link state and use it when ethtool triggers a device self-test. From Andrew Lunn. 5) Start moving away from custom driver versions, use the globally defined kernel version instead, from Leon Romanovsky. 6) Support GRO vis gro_cells in DSA layer, from Alexander Lobakin. 7) Allow hard IRQ deferral during NAPI, from Eric Dumazet. 8) Add sriov and vf support to hinic, from Luo bin. 9) Support Media Redundancy Protocol (MRP) in the bridging code, from Horatiu Vultur. 10) Support netmap in the nft_nat code, from Pablo Neira Ayuso. 11) Allow UDPv6 encapsulation of ESP in the ipsec code, from Sabrina Dubroca. Also add ipv6 support for espintcp. 12) Lots of ReST conversions of the networking documentation, from Mauro Carvalho Chehab. 13) Support configuration of ethtool rxnfc flows in bcmgenet driver, from Doug Berger. 14) Allow to dump cgroup id and filter by it in inet_diag code, from Dmitry Yakunin. 15) Add infrastructure to export netlink attribute policies to userspace, from Johannes Berg. 16) Several optimizations to sch_fq scheduler, from Eric Dumazet. 17) Fallback to the default qdisc if qdisc init fails because otherwise a packet scheduler init failure will make a device inoperative. From Jesper Dangaard Brouer. 18) Several RISCV bpf jit optimizations, from Luke Nelson. 19) Correct the return type of the ->ndo_start_xmit() method in several drivers, it's netdev_tx_t but many drivers were using 'int'. From Yunjian Wang. 20) Add an ethtool interface for PHY master/slave config, from Oleksij Rempel. 21) Add BPF iterators, from Yonghang Song. 22) Add cable test infrastructure, including ethool interfaces, from Andrew Lunn. Marvell PHY driver is the first to support this facility. 23) Remove zero-length arrays all over, from Gustavo A. R. Silva. 24) Calculate and maintain an explicit frame size in XDP, from Jesper Dangaard Brouer. 25) Add CAP_BPF, from Alexei Starovoitov. 26) Support terse dumps in the packet scheduler, from Vlad Buslov. 27) Support XDP_TX bulking in dpaa2 driver, from Ioana Ciornei. 28) Add devm_register_netdev(), from Bartosz Golaszewski. 29) Minimize qdisc resets, from Cong Wang. 30) Get rid of kernel_getsockopt and kernel_setsockopt in order to eliminate set_fs/get_fs calls. From Christoph Hellwig. * git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2517 commits) selftests: net: ip_defrag: ignore EPERM net_failover: fixed rollback in net_failover_open() Revert "tipc: Fix potential tipc_aead refcnt leak in tipc_crypto_rcv" Revert "tipc: Fix potential tipc_node refcnt leak in tipc_rcv" vmxnet3: allow rx flow hash ops only when rss is enabled hinic: add set_channels ethtool_ops support selftests/bpf: Add a default $(CXX) value tools/bpf: Don't use $(COMPILE.c) bpf, selftests: Use bpf_probe_read_kernel s390/bpf: Use bcr 0,%0 as tail call nop filler s390/bpf: Maintain 8-byte stack alignment selftests/bpf: Fix verifier test selftests/bpf: Fix sample_cnt shared between two threads bpf, selftests: Adapt cls_redirect to call csum_level helper bpf: Add csum_level helper for fixing up csum levels bpf: Fix up bpf_skb_adjust_room helper's skb csum setting sfc: add missing annotation for efx_ef10_try_update_nic_stats_vf() crypto/chtls: IPv6 support for inline TLS Crypto/chcr: Fixes a coccinile check error Crypto/chcr: Fixes compilations warnings ...

fs: Introduce DCACHE_DONTCACHE

2020-05-13T15:44:35+00:00

DCACHE_DONTCACHE indicates a dentry should not be cached on final dput(). Also add a helper function to mark DCACHE_DONTCACHE on all dentries pointing to a specific inode when that inode is being set I_DONTCACHE. This facilitates dropping dentry references to inodes sooner which require eviction to swap S_DAX mode. Cc: Al Viro Signed-off-by: Ira Weiny Reviewed-by: Jan Kara Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong

sysctl: pass kernel pointers to ->proc_handler

2020-04-27T06:07:40+00:00

Instead of having all the sysctl handlers deal with user pointers, which is rather hairy in terms of the BPF interaction, copy the input to and from userspace in common code. This also means that the strings are always NUL-terminated by the common code, making the API a little bit safer. As most handler just pass through the data to one of the common handlers a lot of the changes are mechnical. Signed-off-by: Christoph Hellwig Acked-by: Andrey Ignatov Signed-off-by: Al Viro

Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2019-12-08T19:08:28+00:00

Pull misc vfs cleanups from Al Viro: "No common topic, just three cleanups". * 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: make __d_alloc() static fs/namespace: add __user to open_tree and move_mount syscalls fs/fnctl: fix missing __user in fcntl_rw_hint()