kernel/linux.git/include/linux/nfs_fs.h, branch v5.15.209

NFS: don't unhash dentry during unlink/rename

2026-01-19T12:09:37+00:00

[ Upstream commit 3c59366c207e4c6c6569524af606baf017a55c61 ] NFS unlink() (and rename over existing target) must determine if the file is open, and must perform a "silly rename" instead of an unlink (or before rename) if it is. Otherwise the client might hold a file open which has been removed on the server. Consequently if it determines that the file isn't open, it must block any subsequent opens until the unlink/rename has been completed on the server. This is currently achieved by unhashing the dentry. This forces any open attempt to the slow-path for lookup which will block on i_rwsem on the directory until the unlink/rename completes. A future patch will change the VFS to only get a shared lock on i_rwsem for unlink, so this will no longer work. Instead we introduce an explicit interlock. A special value is stored in dentry->d_fsdata while the unlink/rename is running and ->d_revalidate blocks while that value is present. When ->d_revalidate unblocks, the dentry will be invalid. This closes the race without requiring exclusion on i_rwsem. d_fsdata is already used in two different ways. 1/ an IS_ROOT directory dentry might have a "devname" stored in d_fsdata. Such a dentry doesn't have a name and so cannot be the target of unlink or rename. For safety we check if an old devname is still stored, and remove it if it is. 2/ a dentry with DCACHE_NFSFS_RENAMED set will have a 'struct nfs_unlinkdata' stored in d_fsdata. While this is set maydelete() will fail, so an unlink or rename will never proceed on such a dentry. Neither of these can be in effect when a dentry is the target of unlink or rename. So we can expect d_fsdata to be NULL, and store a special value ((void*)1) which is given the name NFS_FSDATA_BLOCKED to indicate that any lookup will be blocked. The d_count() is incremented under d_lock() when a lookup finds the dentry, so we check d_count() is low, and set NFS_FSDATA_BLOCKED under the same lock to avoid any races. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust Stable-dep-of: bd4928ec799b ("NFS: Avoid changing nlink when file removes and attribute updates race") Signed-off-by: Sasha Levin

NFSv3: handle out-of-order write replies.

2024-11-14T12:13:36+00:00

[ Upstream commit 3db63daabe210af32a09533fe7d8d47c711a103c ] NFSv3 includes pre/post wcc attributes which allow the client to determine if all changes to the file have been made by the client itself, or if any might have been made by some other client. If there are gaps in the pre/post ctime sequence it must be assumed that some other client changed the file in that gap and the local cache must be suspect. The next time the file is opened the cache should be invalidated. Since Commit 1c341b777501 ("NFS: Add deferred cache invalidation for close-to-open consistency violations") in linux 5.3 the Linux client has been triggering this invalidation. The chunk in nfs_update_inode() in particularly triggers. Unfortunately Linux NFS assumes that all replies will be processed in the order sent, and will arrive in the order processed. This is not true in general. Consequently Linux NFS might ignore the wcc info in a WRITE reply because the reply is in response to a WRITE that was sent before some other request for which a reply has already been seen. This is detected by Linux using the gencount tests in nfs_inode_attr_cmp(). Also, when the gencount tests pass it is still possible that the request were processed on the server in a different order, and a gap seen in the ctime sequence might be filled in by a subsequent reply, so gaps should not immediately trigger delayed invalidation. The net result is that writing to a server and then reading the file back can result in going to the server for the read rather than serving it from cache - all because a couple of replies arrived out-of-order. This is a performance regression over kernels before 5.3, though the change in 5.3 is a correctness improvement. This has been seen with Linux writing to a Netapp server which occasionally re-orders requests. In testing the majority of requests were in-order, but a few (maybe 2 or three at a time) could be re-ordered. This patch addresses the problem by recording any gaps seen in the pre/post ctime sequence and not triggering invalidation until either there are too many gaps to fit in the table, or until there are no more active writes and the remaining gaps cannot be resolved. We allocate a table of 16 gaps on demand. If the allocation fails we revert to current behaviour which is of little cost as we are unlikely to be able to cache the writes anyway. In the table we store "start->end" pair when iversion is updated and "end<-start" pairs pre/post pairs reported by the server. Usually these exactly cancel out and so nothing is stored. When there are out-of-order replies we do store gaps and these will eventually be cancelled against later replies when this client is the only writer. If the final write is out-of-order there may be one gap remaining when the file is closed. This will be noticed and if there is precisely on gap and if the iversion can be advanced to match it, then we do so. This patch makes no attempt to handle directories correctly. The same problem potentially exists in the out-of-order replies to create/unlink requests can cause future lookup requires to be sent to the server unnecessarily. A similar scheme using the same primitives could be used to notice and handle out-of-order replies. Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker Stable-dep-of: 867da60d463b ("nfs: avoid i_lock contention in nfs_clear_invalid_mapping") Signed-off-by: Sasha Levin

nfs: fix UAF in direct writes

2024-04-10T14:18:40+00:00

[ Upstream commit 17f46b803d4f23c66cacce81db35fef3adb8f2af ] In production we have been hitting the following warning consistently ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 17 PID: 1800359 at lib/refcount.c:28 refcount_warn_saturate+0x9c/0xe0 Workqueue: nfsiod nfs_direct_write_schedule_work [nfs] RIP: 0010:refcount_warn_saturate+0x9c/0xe0 PKRU: 55555554 Call Trace: ? __warn+0x9f/0x130 ? refcount_warn_saturate+0x9c/0xe0 ? report_bug+0xcc/0x150 ? handle_bug+0x3d/0x70 ? exc_invalid_op+0x16/0x40 ? asm_exc_invalid_op+0x16/0x20 ? refcount_warn_saturate+0x9c/0xe0 nfs_direct_write_schedule_work+0x237/0x250 [nfs] process_one_work+0x12f/0x4a0 worker_thread+0x14e/0x3b0 ? ZSTD_getCParams_internal+0x220/0x220 kthread+0xdc/0x120 ? __btf_name_valid+0xa0/0xa0 ret_from_fork+0x1f/0x30 This is because we're completing the nfs_direct_request twice in a row. The source of this is when we have our commit requests to submit, we process them and send them off, and then in the completion path for the commit requests we have if (nfs_commit_end(cinfo.mds)) nfs_direct_write_complete(dreq); However since we're submitting asynchronous requests we sometimes have one that completes before we submit the next one, so we end up calling complete on the nfs_direct_request twice. The only other place we use nfs_generic_commit_list() is in __nfs_commit_inode, which wraps this call in a nfs_commit_begin(); nfs_commit_end(); Which is a common pattern for this style of completion handling, one that is also repeated in the direct code with get_dreq()/put_dreq() calls around where we process events as well as in the completion paths. Fix this by using the same pattern for the commit requests. Before with my 200 node rocksdb stress running this warning would pop every 10ish minutes. With my patch the stress test has been running for several hours without popping. Signed-off-by: Josef Bacik Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin

NFS: Fix WARN_ON due to unionization of nfs_inode.nrequests

2022-09-20T10:39:42+00:00

commit 0ebeebcf59601bcfa0284f4bb7abdec051eb856d upstream. Fixes the following WARN_ON WARNING: CPU: 2 PID: 18678 at fs/nfs/inode.c:123 nfs_clear_inode+0x3b/0x50 [nfs] ... Call Trace: nfs4_evict_inode+0x57/0x70 [nfsv4] evict+0xd1/0x180 dispose_list+0x48/0x60 evict_inodes+0x156/0x190 generic_shutdown_super+0x37/0x110 nfs_kill_super+0x1d/0x40 [nfs] deactivate_locked_super+0x36/0xa0 Signed-off-by: Dave Wysochanski Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman

NFS: Fix another fsync() issue after a server reboot

2022-09-15T09:30:03+00:00

[ Upstream commit 67f4b5dc49913abcdb5cc736e73674e2f352f81d ] Currently, when the writeback code detects a server reboot, it redirties any pages that were not committed to disk, and it sets the flag NFS_CONTEXT_RESEND_WRITES in the nfs_open_context of the file descriptor that dirtied the file. While this allows the file descriptor in question to redrive its own writes, it violates the fsync() requirement that we should be synchronising all writes to disk. While the problem is infrequent, we do see corner cases where an untimely server reboot causes the fsync() call to abandon its attempt to sync data to disk and causing data corruption issues due to missed error conditions or similar. In order to tighted up the client's ability to deal with this situation without introducing livelocks, add a counter that records the number of times pages are redirtied due to a server reboot-like condition, and use that in fsync() to redrive the sync to disk. Fixes: 2197e9b06c22 ("NFS: Fix up fsync() when the server rebooted") Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin

NFS: Save some space in the inode

2022-09-15T09:30:03+00:00

[ Upstream commit e591b298d7ecb851e200f65946e3d53fe78a3c4f ] Save some space in the nfs_inode by setting up an anonymous union with the fields that are peculiar to a specific type of filesystem object. Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin

NFS: Further optimisations for 'ls -l'

2022-09-15T09:30:03+00:00

[ Upstream commit ff81dfb5d721fff87bd516c558847f6effb70031 ] If a user is doing 'ls -l', we have a heuristic in GETATTR that tells the readdir code to try to use READDIRPLUS in order to refresh the inode attributes. In certain cirumstances, we also try to invalidate the remaining directory entries in order to ensure this refresh. If there are multiple readers of the directory, we probably should avoid invalidating the page cache, since the heuristic breaks down in that situation anyway. Signed-off-by: Trond Myklebust Tested-by: Benjamin Coddington Reviewed-by: Benjamin Coddington Signed-off-by: Sasha Levin

NFS: Create a new nfs_alloc_fattr_with_label() function

2022-06-09T08:23:17+00:00

[ Upstream commit d755ad8dc752d44545613ea04d660aed674e540d ] For creating fattrs with the label field already allocated for us. I also update nfs_free_fattr() to free the label in the end. Signed-off-by: Anna Schumaker Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin

NFS: nfsiod should not block forever in mempool_alloc()

2022-04-13T18:59:13+00:00

[ Upstream commit 515dcdcd48736576c6f5c197814da6f81c60a21e ] The concern is that since nfsiod is sometimes required to kick off a commit, it can get locked up waiting forever in mempool_alloc() instead of failing gracefully and leaving the commit until later. Try to allocate from the slab first, with GFP_KERNEL | __GFP_NORETRY, then fall back to a non-blocking attempt to allocate from the memory pool. Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin

NFS: swap IO handling is slightly different for O_DIRECT IO

2022-04-13T18:59:12+00:00

[ Upstream commit 64158668ac8b31626a8ce48db4cad08496eb8340 ] 1/ Taking the i_rwsem for swap IO triggers lockdep warnings regarding possible deadlocks with "fs_reclaim". These deadlocks could, I believe, eventuate if a buffered read on the swapfile was attempted. We don't need coherence with the page cache for a swap file, and buffered writes are forbidden anyway. There is no other need for i_rwsem during direct IO. So never take it for swap_rw() 2/ generic_write_checks() explicitly forbids writes to swap, and performs checks that are not needed for swap. So bypass it for swap_rw(). Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin