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

Nick Huang
2021-05-14T03:59:24Z

From: Yu Hsiang Huang <nickhuang@synology.com>

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@synology.com>
Signed-off-by: Bing Jing Chang <bingjingc@synology.com>
Signed-off-by: Robbie Ko <robbieko@synology.com>
---
fs/nfsd/vfs.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 15adf1f6ab21..39948f130712 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1859,6 +1859,7 @@ 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;

@@ -1887,6 +1888,8 @@ 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;
@@ -1902,6 +1905,8 @@ 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);
--
2.25.1