kernel/linux.git/fs/nfs_common, branch v6.19.12

NFSD: Remove NFSERR_EAGAIN

2026-01-02T18:43:41+00:00

I haven't found an NFSERR_EAGAIN in RFCs 1094, 1813, 7530, or 8881. None of these RFCs have an NFS status code that match the numeric value "11". Based on the meaning of the EAGAIN errno, I presume the use of this status in NFSD means NFS4ERR_DELAY. So replace the one usage of nfserr_eagain, and remove it from NFSD's NFS status conversion tables. As far as I can tell, NFSERR_EAGAIN has existed since the pre-git era, but was not actually used by any code until commit f4e44b393389 ("NFSD: delay unmount source's export after inter-server copy completed."), at which time it become possible for NFSD to return a status code of 11 (which is not valid NFS protocol). Fixes: f4e44b393389 ("NFSD: delay unmount source's export after inter-server copy completed.") Cc: stable@vger.kernel.org Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

NFS/localio: nfs_uuid_put() fix the wake up after unlinking the file

2025-08-05T23:45:40+00:00

Use store_release_wake_up() instead of wake_up_var_locked(), because the waiter cannot retake the nfs_uuid->lock. Acked-by: Mike Snitzer Tested-by: Mike Snitzer Suggested-by: NeilBrown Link: https://lore.kernel.org/all/175262948827.2234665.1891349021754495573@noble.neil.brown.name/ Fixes: 21fb44034695 ("nfs_localio: protect race between nfs_uuid_put() and nfs_close_local_fh()") Signed-off-by: Trond Myklebust

NFS/localio: nfs_uuid_put() fix races with nfs_open/close_local_fh()

2025-08-05T23:45:40+00:00

In order for the wait in nfs_uuid_put() to be safe, it is necessary to ensure that nfs_uuid_add_file() doesn't add a new entry once the nfs_uuid->net has been NULLed out. Also fix up the wake_up_var_locked() / wait_var_event_spinlock() to both use the nfs_uuid address, since nfl, and &nfl->uuid could be used elsewhere. Acked-by: Mike Snitzer Tested-by: Mike Snitzer Link: https://lore.kernel.org/all/175262893035.2234665.1735173020338594784@noble.neil.brown.name/ Fixes: 21fb44034695 ("nfs_localio: protect race between nfs_uuid_put() and nfs_close_local_fh()") Signed-off-by: Trond Myklebust

NFS/localio: nfs_close_local_fh() fix check for file closed

2025-08-05T23:45:39+00:00

If the struct nfs_file_localio is closed, its list entry will be empty, but the nfs_uuid->files list might still contain other entries. Acked-by: Mike Snitzer Tested-by: Mike Snitzer Reviewed-by: NeilBrown Fixes: 21fb44034695 ("nfs_localio: protect race between nfs_uuid_put() and nfs_close_local_fh()") Signed-off-by: Trond Myklebust

nfs_localio: change nfsd_file_put_local() to take a pointer to __rcu pointer

2025-05-28T21:17:14+00:00

Instead of calling xchg() and unrcu_pointer() before nfsd_file_put_local(), we now pass pointer to the __rcu pointer and call xchg() and unrcu_pointer() inside that function. Where unrcu_pointer() is currently called the internals of "struct nfsd_file" are not known and that causes older compilers such as gcc-8 to complain. In some cases we have a __kernel (aka normal) pointer not an __rcu pointer so we need to cast it to __rcu first. This is strictly a weakening so no information is lost. Somewhat surprisingly, this cast is accepted by gcc-8. This has the pleasing result that the cmpxchg() which sets ro_file and rw_file, and also the xchg() which clears them, are both now in the nfsd code. Reported-by: Pali Rohár Reported-by: Vincent Mailhol Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client") Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker

nfs_localio: protect race between nfs_uuid_put() and nfs_close_local_fh()

2025-05-28T21:17:14+00:00

nfs_uuid_put() and nfs_close_local_fh() can race if a "struct nfs_file_localio" is released at the same time that nfsd calls nfs_localio_invalidate_clients(). It is important that neither of these functions completes after the other has started looking at a given nfs_file_localio and before it finishes. If nfs_uuid_put() exits while nfs_close_local_fh() is closing ro_file and rw_file it could return to __nfd_file_cache_purge() while some files are still referenced so the purge may not succeed. If nfs_close_local_fh() exits while nfsd_uuid_put() is still closing the files then the "struct nfs_file_localio" could be freed while nfsd_uuid_put() is still looking at it. This side is currently handled by copying the pointers out of ro_file and rw_file before deleting from the list in nfsd_uuid. We need to preserve this while ensuring that nfsd_uuid_put() does wait for nfs_close_local_fh(). This patch use nfl->uuid and nfl->list to provide the required interlock. nfs_uuid_put() removes the nfs_file_localio from the list, then drops locks and puts the two files, then reclaims the spinlock and sets ->nfs_uuid to NULL. nfs_close_local_fh() operates in the reverse order, setting ->nfs_uuid to NULL, then closing the files, then unlinking from the list. If nfs_uuid_put() finds that ->nfs_uuid is already NULL, it waits for the nfs_file_localio to be removed from the list. If nfs_close_local_fh() find that it has already been unlinked it waits for ->nfs_uuid to become NULL. This ensure that one of the two tries to close the files, but they each waits for the other. As nfs_uuid_put() is making the list empty, change from a list_for_each_safe loop to a while that always takes the first entry. This makes the intent more clear. Also don't move the list to a temporary local list as this would defeat the guarantees required for the interlock. Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client") Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker

nfs_localio: duplicate nfs_close_local_fh()

2025-05-28T21:17:14+00:00

nfs_close_local_fh() is called from two different places for quite different use case. It is called from nfs_uuid_put() when the nfs_uuid is being detached - possibly because the nfs server is not longer serving that filesystem. In this case there will always be an nfs_uuid and so rcu_read_lock() is not needed. It is also called when the nfs_file_localio is no longer needed. In this case there may not be an active nfs_uuid. These two can race, and handling the race properly while avoiding excessive locking will require different handling on each side. This patch prepares the way by opencoding nfs_close_local_fh() into nfs_uuid_put(), then simplifying the code there as befits the context. Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client") Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker

nfs_localio: simplify interface to nfsd for getting nfsd_file

2025-05-28T21:17:14+00:00

The nfsd_localio_operations structure contains nfsd_file_get() to get a reference to an nfsd_file. This is only used in one place, where nfsd_open_local_fh() is also used. This patch combines the two, calling nfsd_open_local_fh() passing a pointer to where the nfsd_file pointer might be stored. If there is a pointer there an nfsd_file_get() can get a reference, that reference is returned. If not a new nfsd_file is acquired, stored at the pointer, and returned. When we store a reference we also increase the refcount on the net, as that refcount is decrements when we clear the stored pointer. We now get an extra reference *before* storing the new nfsd_file at the given location. This avoids possible races with the nfsd_file being freed before the final reference can be taken. This patch moves the rcu_dereference() needed after fetching from ro_file or rw_file into the nfsd code where the 'struct nfs_file' is fully defined. This avoids an error reported by older versions of gcc such as gcc-8 which complain about rcu_dereference() use in contexts where the structure (which will supposedly be accessed) is not fully defined. Reported-by: Pali Rohár Reported-by: Vincent Mailhol Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client") Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker

nfs_localio: always hold nfsd net ref with nfsd_file ref

2025-05-28T21:17:14+00:00

Having separate nfsd_file_put and nfsd_file_put_local in struct nfsd_localio_operations doesn't make much sense. The difference is that nfsd_file_put doesn't drop a reference to the nfs_net which is what keeps nfsd from shutting down. Currently, if nfsd tries to shutdown it will invalidate the files stored in the list from the nfs_uuid and this will drop all references to the nfsd net that the client holds. But the client could still hold some references to nfsd_files for active IO. So nfsd might think is has completely shut down local IO, but hasn't and has no way to wait for those active IO requests to complete. So this patch changes nfsd_file_get to nfsd_file_get_local and has it increase the ref count on the nfsd net and it replaces all calls to ->nfsd_put_file to ->nfsd_put_file_local. It also changes ->nfsd_open_local_fh to return with the refcount on the net elevated precisely when a valid nfsd_file is returned. This means that whenever the client holds a valid nfsd_file, there will be an associated count on the nfsd net, and so the count can only reach zero when all nfsd_files have been returned. nfs_local_file_put() is changed to call nfs_to_nfsd_file_put_local() instead of replacing calls to one with calls to the other because this will help a later patch which changes nfs_to_nfsd_file_put_local() to take an __rcu pointer while nfs_local_file_put() doesn't. Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client") Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker

nfs_localio: use cmpxchg() to install new nfs_file_localio

2025-05-28T21:17:14+00:00

Rather than using nfs_uuid.lock to protect installing a new ro_file or rw_file, change to use cmpxchg(). Removing the file already uses xchg() so this improves symmetry and also makes the code a little simpler. Also remove the optimisation of not taking the lock, and not removing the nfs_file_localio from the linked list, when both ->ro_file and ->rw_file are already NULL. Given that ->nfs_uuid was not NULL, it is extremely unlikely that neither ->ro_file or ->rw_file is NULL so this optimisation can be of little value and it complicates understanding of the code - why can the list_del_init() be skipped? Finally, move the assignment of NULL to ->nfs_uuid until after the last action on the nfs_file_localio (the list_del_init). As soon as this is NULL a racing nfs_close_local_fh() can bypass all the locking and go on to free the nfs_file_localio, so we must be certain to be finished with it first. Fixes: 86e00412254a ("nfs: cache all open LOCALIO nfsd_file(s) in client") Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker