kernel/linux.git/fs/nfsd/filecache.c, branch v6.6.141

nfsd: add list_head nf_gc to struct nfsd_file

2025-01-23T16:21:19+00:00

commit 8e6e2ffa6569a205f1805cbaeca143b556581da6 upstream. nfsd_file_put() in one thread can race with another thread doing garbage collection (running nfsd_file_gc() -> list_lru_walk() -> nfsd_file_lru_cb()): * In nfsd_file_put(), nf->nf_ref is 1, so it tries to do nfsd_file_lru_add(). * nfsd_file_lru_add() returns true (with NFSD_FILE_REFERENCED bit set) * garbage collector kicks in, nfsd_file_lru_cb() clears REFERENCED bit and returns LRU_ROTATE. * garbage collector kicks in again, nfsd_file_lru_cb() now decrements nf->nf_ref to 0, runs nfsd_file_unhash(), removes it from the LRU and adds to the dispose list [list_lru_isolate_move(lru, &nf->nf_lru, head)] * nfsd_file_put() detects NFSD_FILE_HASHED bit is cleared, so it tries to remove the 'nf' from the LRU [if (!nfsd_file_lru_remove(nf))]. The 'nf' has been added to the 'dispose' list by nfsd_file_lru_cb(), so nfsd_file_lru_remove(nf) simply treats it as part of the LRU and removes it, which leads to its removal from the 'dispose' list. * At this moment, 'nf' is unhashed with its nf_ref being 0, and not on the LRU. nfsd_file_put() continues its execution [if (refcount_dec_and_test(&nf->nf_ref))], as nf->nf_ref is already 0, nf->nf_ref is set to REFCOUNT_SATURATED, and the 'nf' gets no chance of being freed. nfsd_file_put() can also race with nfsd_file_cond_queue(): * In nfsd_file_put(), nf->nf_ref is 1, so it tries to do nfsd_file_lru_add(). * nfsd_file_lru_add() sets REFERENCED bit and returns true. * Some userland application runs 'exportfs -f' or something like that, which triggers __nfsd_file_cache_purge() -> nfsd_file_cond_queue(). * In nfsd_file_cond_queue(), it runs [if (!nfsd_file_unhash(nf))], unhash is done successfully. * nfsd_file_cond_queue() runs [if (!nfsd_file_get(nf))], now nf->nf_ref goes to 2. * nfsd_file_cond_queue() runs [if (nfsd_file_lru_remove(nf))], it succeeds. * nfsd_file_cond_queue() runs [if (refcount_sub_and_test(decrement, &nf->nf_ref))] (with "decrement" being 2), so the nf->nf_ref goes to 0, the 'nf' is added to the dispose list [list_add(&nf->nf_lru, dispose)] * nfsd_file_put() detects NFSD_FILE_HASHED bit is cleared, so it tries to remove the 'nf' from the LRU [if (!nfsd_file_lru_remove(nf))], although the 'nf' is not in the LRU, but it is linked in the 'dispose' list, nfsd_file_lru_remove() simply treats it as part of the LRU and removes it. This leads to its removal from the 'dispose' list! * Now nf->ref is 0, unhashed. nfsd_file_put() continues its execution and set nf->nf_ref to REFCOUNT_SATURATED. As shown in the above analysis, using nf_lru for both the LRU list and dispose list can cause the leaks. This patch adds a new list_head nf_gc in struct nfsd_file, and uses it for the dispose list. This does not fix the nfsd_file leaking issue completely. Signed-off-by: Youzhong Yang Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

NFSD: Mark filecache "down" if init fails

2024-10-17T13:24:22+00:00

[ Upstream commit dc0d0f885aa422f621bc1c2124133eff566b0bc8 ] NeilBrown says: > The handling of NFSD_FILE_CACHE_UP is strange. nfsd_file_cache_init() > sets it, but doesn't clear it on failure. So if nfsd_file_cache_init() > fails for some reason, nfsd_file_cache_shutdown() would still try to > clean up if it was called. Reported-by: NeilBrown Fixes: c7b824c3d06c ("NFSD: Replace the "init once" mechanism") Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

nfsd: fix refcount leak when file is unhashed after being found

2024-10-04T14:29:32+00:00

[ Upstream commit 8a7926176378460e0d91e02b03f0ff20a8709a60 ] If we wait_for_construction and find that the file is no longer hashed, and we're going to retry the open, the old nfsd_file reference is currently leaked. Put the reference before retrying. Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of lease break error") Signed-off-by: Jeff Layton Tested-by: Youzhong Yang Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

nfsd: remove unneeded EEXIST error check in nfsd_do_file_acquire

2024-10-04T14:29:32+00:00

[ Upstream commit 81a95c2b1d605743220f28db04b8da13a65c4059 ] Given that we do the search and insertion while holding the i_lock, I don't think it's possible for us to get EEXIST here. Remove this case. Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of lease break error") Signed-off-by: Jeff Layton Tested-by: Youzhong Yang Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

nfsd: Handle EOPENSTALE correctly in the filecache

2023-11-20T10:58:52+00:00

[ Upstream commit d59b3515ab021e010fdc58a8f445ea62dd2f7f4c ] The nfsd_open code handles EOPENSTALE correctly, by retrying the call to fh_verify() and __nfsd_open(). However the filecache just drops the error on the floor, and immediately returns nfserr_stale to the caller. This patch ensures that we propagate the EOPENSTALE code back to nfsd_file_do_acquire, and that we handle it correctly. Fixes: 65294c1f2c5e ("nfsd: add a new struct file caching facility to nfsd") Signed-off-by: Trond Myklebust Reviewed-by: Jeff Layton Message-Id: <20230911183027.11372-1-trond.myklebust@hammerspace.com> Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

NFSD: Fix problem of COMMIT and NFS4ERR_DELAY in infinite loop

2023-04-27T22:49:24+00:00

The following request sequence to the same file causes the NFS client and server getting into an infinite loop with COMMIT and NFS4ERR_DELAY: OPEN REMOVE WRITE COMMIT Problem reported by recall11, recall12, recall14, recall20, recall22, recall40, recall42, recall48, recall50 of nfstest suite. This patch restores the handling of race condition in nfsd_file_do_acquire with unlink to that prior of the regression. Fixes: ac3a2585f018 ("nfsd: rework refcounting in filecache") Signed-off-by: Dai Ngo Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

nfsd: simplify the delayed disposal list code

2023-04-26T13:05:01+00:00

When queueing a dispose list to the appropriate "freeme" lists, it pointlessly queues the objects one at a time to an intermediate list. Remove a few helpers and just open code a list_move to make it more clear and efficient. Better document the resulting functions with kerneldoc comments. Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever

NFSD: Convert filecache to rhltable

2023-04-26T13:04:59+00:00

While we were converting the nfs4_file hashtable to use the kernel's resizable hashtable data structure, Neil Brown observed that the list variant (rhltable) would be better for managing nfsd_file items as well. The nfsd_file hash table will contain multiple entries for the same inode -- these should be kept together on a list. And, it could be possible for exotic or malicious client behavior to cause the hash table to resize itself on every insertion. A nice simplification is that rhltable_lookup() can return a list that contains only nfsd_file items that match a given inode, which enables us to eliminate specialized hash table helper functions and use the default functions provided by the rhashtable implementation). Since we are now storing nfsd_file items for the same inode on a single list, that effectively reduces the number of hash entries that have to be tracked in the hash table. The mininum bucket count is therefore lowered. Light testing with fstests generic/531 show no regressions. Suggested-by: Neil Brown Signed-off-by: Chuck Lever

nfsd: allow reaping files still under writeback

2023-04-26T13:04:59+00:00

On most filesystems, there is no reason to delay reaping an nfsd_file just because its underlying inode is still under writeback. nfsd just relies on client activity or the local flusher threads to do writeback. The main exception is NFS, which flushes all of its dirty data on last close. Add a new EXPORT_OP_FLUSH_ON_CLOSE flag to allow filesystems to signal that they do this, and only skip closing files under writeback on such filesystems. Also, remove a redundant NULL file pointer check in nfsd_file_check_writeback, and clean up nfs's export op flag definitions. Signed-off-by: Jeff Layton Acked-by: Anna Schumaker Signed-off-by: Chuck Lever

nfsd: update comment over __nfsd_file_cache_purge

2023-04-26T13:04:59+00:00

Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever