6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mike Snitzer [ Upstream commit 67435d2d8a33a75f9647724952cb1b18279d2e95 ] LOCALIO is an NFS loopback mount optimization that avoids using the network for READ, WRITE and COMMIT if the NFS client and server are determined to be on the same system. But because LOCALIO is still fundamentally "just NFS loopback mount" it is susceptible to recursion deadlock via direct reclaim, e.g.: NFS LOCALIO down to XFS and then back into NFS via nfs_writepages. Fix LOCALIO's potential for direct reclaim deadlock by ensuring that all its page cache allocations are done from GFP_NOFS context. Thanks to Ben Coddington for pointing out commit ad22c7a043c2 ("xfs: prevent stack overflows from page cache allocation"). Reported-by: John Cagle Tested-by: Allen Lu Suggested-by: Benjamin Coddington Fixes: 70ba381e1a43 ("nfs: add LOCALIO support") Signed-off-by: Mike Snitzer Signed-off-by: Anna Schumaker Signed-off-by: Sasha Levin --- fs/nfs/localio.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c index c59f205b51308..fe76b8a9f2e67 100644 --- a/fs/nfs/localio.c +++ b/fs/nfs/localio.c @@ -270,6 +270,18 @@ nfs_bvec_alloc_and_import_pagevec(struct page **pagevec, return bvec; } +/* + * Ensure all page cache allocations are done from GFP_NOFS context to + * prevent direct reclaim recursion back into NFS via nfs_writepages. + */ +static void +nfs_local_mapping_set_gfp_nofs_context(struct address_space *m) +{ + gfp_t gfp_mask = mapping_gfp_mask(m); + + mapping_set_gfp_mask(m, (gfp_mask & ~(__GFP_FS))); +} + static void nfs_local_iocb_free(struct nfs_local_kiocb *iocb) { @@ -293,6 +305,7 @@ nfs_local_iocb_alloc(struct nfs_pgio_header *hdr, return NULL; } + nfs_local_mapping_set_gfp_nofs_context(file->f_mapping); if (localio_O_DIRECT_semantics && test_bit(NFS_IOHDR_ODIRECT, &hdr->flags)) { iocb->kiocb.ki_filp = file; @@ -734,6 +747,8 @@ nfs_local_run_commit(struct file *filp, struct nfs_commit_data *data) end = LLONG_MAX; } + nfs_local_mapping_set_gfp_nofs_context(filp->f_mapping); + dprintk("%s: commit %llu - %llu\n", __func__, start, end); return vfs_fsync_range(filp, start, end, 0); } -- 2.53.0