kernel/linux.git/fs/nfs/super.c, branch linux-7.1.y

NFS: Fix RCU dereference of cl_xprt in nfs_compare_super_address

2026-04-22T12:53:23+00:00

The cl_xprt pointer in struct rpc_clnt is marked as __rcu. Accessing it directly in nfs_compare_super_address() is unsafe and triggers Sparse warnings. Fix this by using rcu_dereference() within an RCU read-side critical section to retrieve the transport pointer. This addresses the sparse warning and ensures atomic access to the pointer, as the transport can be updated via transport switching even while the superblock remains active under sb_lock. Fixes: 7e3fcf61abde ("nfs: don't share mounts between network namespaces") Signed-off-by: Sean Chang Signed-off-by: Trond Myklebust

NFS: Merge CONFIG_NFS_V4_1 with CONFIG_NFS_V4

2026-01-30T16:42:21+00:00

Compiling the NFSv4 module without any minorversion support doesn't make much sense, so this patch sets NFS v4.1 as the default, always enabled NFS version allowing us to replace all the CONFIG_NFS_V4_1s scattered throughout the code with CONFIG_NFS_V4. Signed-off-by: Anna Schumaker

NFS: remove __nfs_client_for_each_server

2026-01-20T19:49:45+00:00

__nfs_client_for_each_server is only called by nfs_client_for_each_server, so merge the two. Signed-off-by: Christoph Hellwig Signed-off-by: Anna Schumaker

NFS: Fix inheritance of the block sizes when automounting

2025-11-29T22:23:03+00:00

Only inherit the block sizes that were actually specified as mount parameters for the parent mount. Fixes: 62a55d088cd8 ("NFS: Additional refactoring for fs_context conversion") Signed-off-by: Trond Myklebust

NFS: Automounted filesystems should inherit ro,noexec,nodev,sync flags

2025-11-29T22:22:48+00:00

When a filesystem is being automounted, it needs to preserve the user-set superblock mount options, such as the "ro" flag. Reported-by: Li Lingfeng Link: https://lore.kernel.org/all/20240604112636.236517-3-lilingfeng@huaweicloud.com/ Fixes: f2aedb713c28 ("NFS: Add fs_context support.") Signed-off-by: Trond Myklebust

Revert "nfs: clear SB_RDONLY before getting superblock"

2025-11-29T22:22:32+00:00

This reverts commit 8cd9b785943c57a136536250da80ba1eb6f8eb18. Silently ignoring the "ro" and "rw" mount options causes user confusion, and regressions. Reported-by: Alkis Georgopoulos Cc: Li Lingfeng Fixes: 8cd9b785943c ("nfs: clear SB_RDONLY before getting superblock") Signed-off-by: Trond Myklebust

Revert "nfs: ignore SB_RDONLY when remounting nfs"

2025-11-29T22:19:01+00:00

This reverts commit 80c4de6ab44c14e910117a02f2f8241ffc6ec54a. Silently ignoring the "ro" and "rw" mount options causes user confusion, and regressions. Reported-by: Alkis Georgopoulos Cc: Li Lingfeng Fixes: 80c4de6ab44c ("nfs: ignore SB_RDONLY when remounting nfs") Signed-off-by: Trond Myklebust

new helper: set_default_d_op()

2025-06-11T02:21:16+00:00

... to be used instead of manually assigning to ->s_d_op. All in-tree filesystem converted (and field itself is renamed, so any out-of-tree ones in need of conversion will be caught by compiler). Reviewed-by: Christian Brauner Signed-off-by: Al Viro

nfs: ignore SB_RDONLY when remounting nfs

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

In some scenarios, when mounting NFS, more than one superblock may be created. The final superblock used is the last one created, but only the first superblock carries the ro flag passed from user space. If a ro flag is added to the superblock via remount, it will trigger the issue described in Link[1]. Link[2] attempted to address this by marking the superblock as ro during the initial mount. However, this introduced a new problem in scenarios where multiple mount points share the same superblock: [root@a ~]# mount /dev/sdb /mnt/sdb [root@a ~]# echo "/mnt/sdb *(rw,no_root_squash)" > /etc/exports [root@a ~]# echo "/mnt/sdb/test_dir2 *(ro,no_root_squash)" >> /etc/exports [root@a ~]# systemctl restart nfs-server [root@a ~]# mount -t nfs -o rw 127.0.0.1:/mnt/sdb/test_dir1 /mnt/test_mp1 [root@a ~]# mount | grep nfs4 127.0.0.1:/mnt/sdb/test_dir1 on /mnt/test_mp1 type nfs4 (rw,relatime,... [root@a ~]# mount -t nfs -o ro 127.0.0.1:/mnt/sdb/test_dir2 /mnt/test_mp2 [root@a ~]# mount | grep nfs4 127.0.0.1:/mnt/sdb/test_dir1 on /mnt/test_mp1 type nfs4 (ro,relatime,... 127.0.0.1:/mnt/sdb/test_dir2 on /mnt/test_mp2 type nfs4 (ro,relatime,... [root@a ~]# When mounting the second NFS, the shared superblock is marked as ro, causing the previous NFS mount to become read-only. To resolve both issues, the ro flag is no longer applied to the superblock during remount. Instead, the ro flag on the mount is used to control whether the mount point is read-only. Fixes: 281cad46b34d ("NFS: Create a submount rpc_op") Link[1]: https://lore.kernel.org/all/20240604112636.236517-3-lilingfeng@huaweicloud.com/ Link[2]: https://lore.kernel.org/all/20241130035818.1459775-1-lilingfeng3@huawei.com/ Signed-off-by: Li Lingfeng Signed-off-by: Anna Schumaker

nfs: clear SB_RDONLY before getting superblock

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

As described in the link, commit 52cb7f8f1778 ("nfs: ignore SB_RDONLY when mounting nfs") removed the check for the ro flag when determining whether to share the superblock, which caused issues when mounting different subdirectories under the same export directory via NFSv3. However, this change did not affect NFSv4. For NFSv3: 1) A single superblock is created for the initial mount. 2) When mounted read-only, this superblock carries the SB_RDONLY flag. 3) Before commit 52cb7f8f1778 ("nfs: ignore SB_RDONLY when mounting nfs"): Subsequent rw mounts would not share the existing ro superblock due to flag mismatch, creating a new superblock without SB_RDONLY. After the commit: The SB_RDONLY flag is ignored during superblock comparison, and this leads to sharing the existing superblock even for rw mounts. Ultimately results in write operations being rejected at the VFS layer. For NFSv4: 1) Multiple superblocks are created and the last one will be kept. 2) The actually used superblock for ro mounts doesn't carry SB_RDONLY flag. Therefore, commit 52cb7f8f1778 doesn't affect NFSv4 mounts. Clear SB_RDONLY before getting superblock when NFS_MOUNT_UNSHARED is not set to fix it. Fixes: 52cb7f8f1778 ("nfs: ignore SB_RDONLY when mounting nfs") Closes: https://lore.kernel.org/all/12d7ea53-1202-4e21-a7ef-431c94758ce5@app.fastmail.com/T/ Signed-off-by: Li Lingfeng Signed-off-by: Anna Schumaker