[PATCH 6.12 009/139] NFS: Fix a deadlock involving nfs_release_folio()
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2026-01-21 18:18:28
Also in:
linux-patches
Subsystem:
filesystems (vfs and infrastructure), nfs, sunrpc, and lockd clients, the rest · Maintainers:
Alexander Viro, Christian Brauner, Trond Myklebust, Anna Schumaker, Linus Torvalds
6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Trond Myklebust <redacted>
[ Upstream commit cce0be6eb4971456b703aaeafd571650d314bcca ]
Wang Zhaolong reports a deadlock involving NFSv4.1 state recovery
waiting on kthreadd, which is attempting to reclaim memory by calling
nfs_release_folio(). The latter cannot make progress due to state
recovery being needed.
It seems that the only safe thing to do here is to kick off a writeback
of the folio, without waiting for completion, or else kicking off an
asynchronous commit.
Reported-by: Wang Zhaolong <redacted>
Fixes: 96780ca55e3c ("NFS: fix up nfs_release_folio() to try to release the page")
Signed-off-by: Trond Myklebust <redacted>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/file.c | 3 ++-
fs/nfs/nfstrace.h | 3 +++
fs/nfs/write.c | 33 +++++++++++++++++++++++++++++++++
include/linux/nfs_fs.h | 1 +
4 files changed, 39 insertions(+), 1 deletion(-)
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index a16a619fb8c33..7d1840cea4444 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c@@ -461,7 +461,8 @@ static bool nfs_release_folio(struct folio *folio, gfp_t gfp) if ((current_gfp_context(gfp) & GFP_KERNEL) != GFP_KERNEL || current_is_kswapd() || current_is_kcompactd()) return false; - if (nfs_wb_folio(folio->mapping->host, folio) < 0) + if (nfs_wb_folio_reclaim(folio->mapping->host, folio) < 0 || + folio_test_private(folio)) return false; } return nfs_fscache_release_folio(folio, gfp);
diff --git a/fs/nfs/nfstrace.h b/fs/nfs/nfstrace.h
index 1eab98c277fab..2989b6f284ff4 100644
--- a/fs/nfs/nfstrace.h
+++ b/fs/nfs/nfstrace.h@@ -1039,6 +1039,9 @@ DECLARE_EVENT_CLASS(nfs_folio_event_done, DEFINE_NFS_FOLIO_EVENT(nfs_aop_readpage); DEFINE_NFS_FOLIO_EVENT_DONE(nfs_aop_readpage_done); +DEFINE_NFS_FOLIO_EVENT(nfs_writeback_folio_reclaim); +DEFINE_NFS_FOLIO_EVENT_DONE(nfs_writeback_folio_reclaim_done); + DEFINE_NFS_FOLIO_EVENT(nfs_writeback_folio); DEFINE_NFS_FOLIO_EVENT_DONE(nfs_writeback_folio_done);
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 88d0e5168093a..48a8866220d1a 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c@@ -2065,6 +2065,39 @@ int nfs_wb_folio_cancel(struct inode *inode, struct folio *folio) return ret; } +/** + * nfs_wb_folio_reclaim - Write back all requests on one page + * @inode: pointer to page + * @folio: pointer to folio + * + * Assumes that the folio has been locked by the caller + */ +int nfs_wb_folio_reclaim(struct inode *inode, struct folio *folio) +{ + loff_t range_start = folio_pos(folio); + size_t len = folio_size(folio); + struct writeback_control wbc = { + .sync_mode = WB_SYNC_ALL, + .nr_to_write = 0, + .range_start = range_start, + .range_end = range_start + len - 1, + .for_sync = 1, + }; + int ret; + + if (folio_test_writeback(folio)) + return -EBUSY; + if (folio_clear_dirty_for_io(folio)) { + trace_nfs_writeback_folio_reclaim(inode, range_start, len); + ret = nfs_writepage_locked(folio, &wbc); + trace_nfs_writeback_folio_reclaim_done(inode, range_start, len, + ret); + return ret; + } + nfs_commit_inode(inode, 0); + return 0; +} + /** * nfs_wb_folio - Write back all requests on one page * @inode: pointer to page
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 039898d70954f..8d2cf10294a42 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h@@ -610,6 +610,7 @@ extern int nfs_update_folio(struct file *file, struct folio *folio, extern int nfs_sync_inode(struct inode *inode); extern int nfs_wb_all(struct inode *inode); extern int nfs_wb_folio(struct inode *inode, struct folio *folio); +extern int nfs_wb_folio_reclaim(struct inode *inode, struct folio *folio); int nfs_wb_folio_cancel(struct inode *inode, struct folio *folio); extern int nfs_commit_inode(struct inode *, int); extern struct nfs_commit_data *nfs_commitdata_alloc(void);
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2.51.0