[Devel] [PATCH] fs/fuse kio: satisfy pure FALLOC_FL_KEEP_SIZE immediately

[Pavel Butsykin]

Fallocate without mutex lock can race with setattr size request, as a result,
may be various problems, including incorrectly changed file size. At the same
time pure FALLOC_FL_KEEP_SIZE for vstorage is just nope, so we can immediately
complete fallocate with mode == FALLOC_FL_KEEP_SIZE. Also move mutex_is_locked,
since all other mode combinations either have to be under mutex or not valid.

#VSTOR-19317

Signed-off-by: Pavel Butsykin <pbutsykin at virtuozzo.com>
---
 fs/fuse/kio/pcs/pcs_fuse_kdirect.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/kio/pcs/pcs_fuse_kdirect.c b/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
index de54fedeb5e4..89866370a341 100644
--- a/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
+++ b/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
@@ -924,9 +924,11 @@ static void pcs_fuse_submit(struct pcs_fuse_cluster *pfc, struct fuse_req *req,
 		if (inarg->offset >= di->fileinfo.attr.size)
 			inarg->mode &= ~FALLOC_FL_ZERO_RANGE;
 
+		if (inarg->mode == FALLOC_FL_KEEP_SIZE)
+			break; /* NOPE */
+
+		WARN_ON_ONCE(!mutex_is_locked(&fi->inode.i_mutex));
 		if (inarg->mode & (FALLOC_FL_ZERO_RANGE|FALLOC_FL_PUNCH_HOLE)) {
-			WARN_ON_ONCE(!mutex_is_locked(&fi->inode.i_mutex));
-
 			if ((inarg->offset & (PAGE_SIZE - 1)) || (inarg->length & (PAGE_SIZE - 1))) {
 				r->req.out.h.error = -EINVAL;
 				goto error;
-- 
2.15.1