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[PATCH 104/104] virtiofsd: Convert lo_destroy to take the lo->mutex lock
From: |
Dr. David Alan Gilbert (git) |
Subject: |
[PATCH 104/104] virtiofsd: Convert lo_destroy to take the lo->mutex lock itself |
Date: |
Thu, 12 Dec 2019 16:39:04 +0000 |
From: "Dr. David Alan Gilbert" <address@hidden>
lo_destroy was relying on some implicit knowledge of the locking;
we can avoid this if we create an unref_inode that doesn't take
the lock and then grab it for the whole of the lo_destroy.
Suggested-by: Vivek Goyal <address@hidden>
Signed-off-by: Dr. David Alan Gilbert <address@hidden>
---
tools/virtiofsd/passthrough_ll.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 38f4948e61..c37f57157e 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -1328,14 +1328,13 @@ static void lo_unlink(fuse_req_t req, fuse_ino_t
parent, const char *name)
lo_inode_put(lo, &inode);
}
-static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode,
- uint64_t n)
+/* To be called with lo->mutex held */
+static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n)
{
if (!inode) {
return;
}
- pthread_mutex_lock(&lo->mutex);
assert(inode->nlookup >= n);
inode->nlookup -= n;
if (!inode->nlookup) {
@@ -1346,15 +1345,24 @@ static void unref_inode_lolocked(struct lo_data *lo,
struct lo_inode *inode,
}
g_hash_table_destroy(inode->posix_locks);
pthread_mutex_destroy(&inode->plock_mutex);
- pthread_mutex_unlock(&lo->mutex);
/* Drop our refcount from lo_do_lookup() */
lo_inode_put(lo, &inode);
- } else {
- pthread_mutex_unlock(&lo->mutex);
}
}
+static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode,
+ uint64_t n)
+{
+ if (!inode) {
+ return;
+ }
+
+ pthread_mutex_lock(&lo->mutex);
+ unref_inode(lo, inode, n);
+ pthread_mutex_unlock(&lo->mutex);
+}
+
static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup)
{
struct lo_data *lo = lo_data(req);
@@ -2441,13 +2449,7 @@ static void lo_destroy(void *userdata)
{
struct lo_data *lo = (struct lo_data *)userdata;
- /*
- * Normally lo->mutex must be taken when traversing lo->inodes but
- * lo_destroy() is a serialized request so no races are possible here.
- *
- * In addition, we cannot acquire lo->mutex since unref_inode() takes it
- * too and this would result in a recursive lock.
- */
+ pthread_mutex_lock(&lo->mutex);
while (true) {
GHashTableIter iter;
gpointer key, value;
@@ -2458,8 +2460,9 @@ static void lo_destroy(void *userdata)
}
struct lo_inode *inode = value;
- unref_inode_lolocked(lo, inode, inode->nlookup);
+ unref_inode(lo, inode, inode->nlookup);
}
+ pthread_mutex_unlock(&lo->mutex);
}
static struct fuse_lowlevel_ops lo_oper = {
--
2.23.0
- [PATCH 095/104] virtiofsd: convert more fprintf and perror to use fuse log infra, (continued)
- [PATCH 095/104] virtiofsd: convert more fprintf and perror to use fuse log infra, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 093/104] virtiofsd: introduce inode refcount to prevent use-after-free, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 096/104] virtiofsd: Reset O_DIRECT flag during file open, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 097/104] virtiofsd: Fix data corruption with O_APPEND wirte in writeback mode, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 098/104] virtiofsd: add definition of fuse_buf_writev(), Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 099/104] virtiofsd: use fuse_buf_writev to replace fuse_buf_write for better performance, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 102/104] virtiofsd: fix lo_destroy() resource leaks, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 103/104] virtiofsd: add --thread-pool-size=NUM option, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 101/104] virtiofsd: prevent FUSE_INIT/FUSE_DESTROY races, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 100/104] virtiofsd: process requests in a thread pool, Dr. David Alan Gilbert (git), 2019/12/12
- [PATCH 104/104] virtiofsd: Convert lo_destroy to take the lo->mutex lock itself,
Dr. David Alan Gilbert (git) <=
- Re: [PATCH 000/104] virtiofs daemon [all], no-reply, 2019/12/12