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NFS: Fix a deadlock involving nfs_release_folio()

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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 <wangzhaolong@huaweicloud.com>
Fixes: 96780ca55e ("NFS: fix up nfs_release_folio() to try to release the page")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust
2025-12-31 11:42:31 -05:00
parent 857bf90562
commit cce0be6eb4
4 changed files with 39 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
fs/nfs/file.c
View File

@@ -511,7 +511,8 @@ 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);

3
fs/nfs/nfstrace.h
View File

@@ -1062,6 +1062,9 @@ 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);

33
fs/nfs/write.c
View File

@@ -2024,6 +2024,39 @@ 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

1
include/linux/nfs_fs.h
View File

@@ -637,6 +637,7 @@ 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);