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authorJeff Layton <jeff.layton@primarydata.com>2020-11-30 17:03:16 -0500
committerChuck Lever <chuck.lever@oracle.com>2020-12-09 09:39:38 -0500
commit7f84b488f9add1d5cca3e6197c95914c7bd3c1cf (patch)
treefe4616aeb70a824182f6fecd22a8ef6c38786ad7 /fs/nfsd
parentba5e8187c55555519ae0b63c0fb681391bc42af9 (diff)
downloadlinux-7f84b488f9add1d5cca3e6197c95914c7bd3c1cf.tar.bz2
nfsd: close cached files prior to a REMOVE or RENAME that would replace target
It's not uncommon for some workloads to do a bunch of I/O to a file and delete it just afterward. If knfsd has a cached open file however, then the file may still be open when the dentry is unlinked. If the underlying filesystem is nfs, then that could trigger it to do a sillyrename. On a REMOVE or RENAME scan the nfsd_file cache for open files that correspond to the inode, and proactively unhash and put their references. This should prevent any delete-on-last-close activity from occurring, solely due to knfsd's open file cache. This must be done synchronously though so we use the variants that call flush_delayed_fput. There are deadlock possibilities if you call flush_delayed_fput while holding locks, however. In the case of nfsd_rename, we don't even do the lookups of the dentries to be renamed until we've locked for rename. Once we've figured out what the target dentry is for a rename, check to see whether there are cached open files associated with it. If there are, then unwind all of the locking, close them all, and then reattempt the rename. None of this is really necessary for "typical" filesystems though. It's mostly of use for NFS, so declare a new export op flag and use that to determine whether to close the files beforehand. Signed-off-by: Jeff Layton <jeff.layton@primarydata.com> Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Diffstat (limited to 'fs/nfsd')
-rw-r--r--fs/nfsd/vfs.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 1ecaceebee13..79cba942087e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1724,7 +1724,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
struct inode *fdir, *tdir;
__be32 err;
int host_err;
- bool has_cached = false;
+ bool close_cached = false;
err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
if (err)
@@ -1783,8 +1783,9 @@ retry:
if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
goto out_dput_new;
- if (nfsd_has_cached_files(ndentry)) {
- has_cached = true;
+ if ((ndentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK) &&
+ nfsd_has_cached_files(ndentry)) {
+ close_cached = true;
goto out_dput_old;
} else {
host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
@@ -1805,7 +1806,7 @@ retry:
* as that would do the wrong thing if the two directories
* were the same, so again we do it by hand.
*/
- if (!has_cached) {
+ if (!close_cached) {
fill_post_wcc(ffhp);
fill_post_wcc(tfhp);
}
@@ -1819,8 +1820,8 @@ retry:
* shouldn't be done with locks held however, so we delay it until this
* point and then reattempt the whole shebang.
*/
- if (has_cached) {
- has_cached = false;
+ if (close_cached) {
+ close_cached = false;
nfsd_close_cached_files(ndentry);
dput(ndentry);
goto retry;
@@ -1872,7 +1873,8 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
type = d_inode(rdentry)->i_mode & S_IFMT;
if (type != S_IFDIR) {
- nfsd_close_cached_files(rdentry);
+ if (rdentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK)
+ nfsd_close_cached_files(rdentry);
host_err = vfs_unlink(dirp, rdentry, NULL);
} else {
host_err = vfs_rmdir(dirp, rdentry);