Patch "nfsd: Prevent truncation of an unlinked inode from blocking access to its directory" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    nfsd: Prevent truncation of an unlinked inode from blocking access to its directory

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-prevent-truncation-of-an-unlinked-inode-from-bl.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4b4b2f629e1ade8fd1e7c7aef5ef0b62981520a5
Author: Yu Hsiang Huang <nickhuang@xxxxxxxxxxxx>
Date:   Fri May 14 11:58:29 2021 +0800

    nfsd: Prevent truncation of an unlinked inode from blocking access to its directory
    
    [ Upstream commit e5d74a2d0ee67ae00edad43c3d7811016e4d2e21 ]
    
    Truncation of an unlinked inode may take a long time for I/O waiting, and
    it doesn't have to prevent access to the directory. Thus, let truncation
    occur outside the directory's mutex, just like do_unlinkat() does.
    
    Signed-off-by: Yu Hsiang Huang <nickhuang@xxxxxxxxxxxx>
    Signed-off-by: Bing Jing Chang <bingjingc@xxxxxxxxxxxx>
    Signed-off-by: Robbie Ko <robbieko@xxxxxxxxxxxx>
    Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 520e55c35e742..2eb3bfbc8a35f 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1870,6 +1870,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 {
 	struct dentry	*dentry, *rdentry;
 	struct inode	*dirp;
+	struct inode	*rinode;
 	__be32		err;
 	int		host_err;
 
@@ -1898,6 +1899,8 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 		host_err = -ENOENT;
 		goto out_drop_write;
 	}
+	rinode = d_inode(rdentry);
+	ihold(rinode);
 
 	if (!type)
 		type = d_inode(rdentry)->i_mode & S_IFMT;
@@ -1913,6 +1916,8 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 	if (!host_err)
 		host_err = commit_metadata(fhp);
 	dput(rdentry);
+	fh_unlock(fhp);
+	iput(rinode);    /* truncate the inode here */
 
 out_drop_write:
 	fh_drop_write(fhp);