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Message-ID: <20140826084149.30577.27364.stgit@localhost.localdomain>
Date: Tue, 26 Aug 2014 12:42:52 +0400
From: Maxim Patlasov <MPatlasov@...allels.com>
To: miklos@...redi.hu
Cc: fuse-devel@...ts.sourceforge.net, avati@...ster.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 3/6] fuse: wait for end of IO on release (v2)
There are two types of I/O activity that can be "in progress" at the time
of fuse_release() execution: asynchronous read-ahead and write-back. The
patch ensures that they are completed before fuse_release_common sends
FUSE_RELEASE to userspace.
So far as fuse_release() waits for end of async I/O, its callbacks
(fuse_readpages_end and fuse_writepage_finish) calling fuse_file_put cannot
be the last holders of fuse file anymore. To emphasize the fact, the patch
replaces fuse_file_put with __fuse_file_put there.
Changed in v2 (thanks to Miklos):
- removed redundant locking around __fuse_file_put()
Signed-off-by: Maxim Patlasov <mpatlasov@...allels.com>
---
fs/fuse/file.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 66 insertions(+), 5 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 7723b3f..8713e62 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -149,6 +149,17 @@ static void fuse_file_put(struct fuse_file *ff, bool sync)
}
}
+/*
+ * Asynchronous callbacks may use it instead of fuse_file_put() because
+ * we guarantee that they are never last holders of ff. Hitting BUG() below
+ * will make clear any violation of the guarantee.
+ */
+static void __fuse_file_put(struct fuse_file *ff)
+{
+ if (atomic_dec_and_test(&ff->count))
+ BUG();
+}
+
int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
bool isdir)
{
@@ -279,6 +290,11 @@ static void fuse_prepare_release(struct fuse_file *ff, int flags, int opcode)
req->in.args[0].value = inarg;
}
+static bool must_release_synchronously(struct fuse_file *ff)
+{
+ return ff->open_flags & FOPEN_SYNC_RELEASE;
+}
+
void fuse_release_common(struct file *file, int opcode)
{
struct fuse_file *ff;
@@ -302,6 +318,13 @@ void fuse_release_common(struct file *file, int opcode)
req->misc.release.path = file->f_path;
/*
+ * No more in-flight asynchronous READ or WRITE requests if
+ * fuse file release is synchronous
+ */
+ if (must_release_synchronously(ff))
+ BUG_ON(atomic_read(&ff->count) != 1);
+
+ /*
* Normally this will send the RELEASE request, however if
* some asynchronous READ or WRITE requests are outstanding,
* the sending will be delayed.
@@ -321,11 +344,34 @@ static int fuse_open(struct inode *inode, struct file *file)
static int fuse_release(struct inode *inode, struct file *file)
{
struct fuse_conn *fc = get_fuse_conn(inode);
+ struct fuse_file *ff = file->private_data;
/* see fuse_vma_close() for !writeback_cache case */
if (fc->writeback_cache)
write_inode_now(inode, 1);
+ if (must_release_synchronously(ff)) {
+ struct fuse_inode *fi = get_fuse_inode(inode);
+
+ /*
+ * Must remove file from write list. Otherwise it is possible
+ * this file will get more writeback from another files
+ * rerouted via write_files.
+ */
+ spin_lock(&ff->fc->lock);
+ list_del_init(&ff->write_entry);
+ spin_unlock(&ff->fc->lock);
+
+ wait_event(fi->page_waitq, atomic_read(&ff->count) == 1);
+
+ /*
+ * spin_unlock_wait(&ff->fc->lock) would be natural here to
+ * wait for threads just released ff to leave their critical
+ * sections. But taking spinlock is the first thing
+ * fuse_release_common does, so that this is unnecessary.
+ */
+ }
+
fuse_release_common(file, FUSE_RELEASE);
/* return value is ignored by VFS */
@@ -823,8 +869,15 @@ static void fuse_readpages_end(struct fuse_conn *fc, struct fuse_req *req)
unlock_page(page);
page_cache_release(page);
}
- if (req->ff)
- fuse_file_put(req->ff, false);
+ if (req->ff) {
+ if (must_release_synchronously(req->ff)) {
+ struct fuse_inode *fi = get_fuse_inode(req->inode);
+
+ __fuse_file_put(req->ff);
+ wake_up(&fi->page_waitq);
+ } else
+ fuse_file_put(req->ff, false);
+ }
}
struct fuse_fill_data {
@@ -851,6 +904,7 @@ static void fuse_send_readpages(struct fuse_fill_data *data)
if (fc->async_read) {
req->ff = fuse_file_get(ff);
req->end = fuse_readpages_end;
+ req->inode = data->inode;
fuse_request_send_background(fc, req);
} else {
fuse_request_send(fc, req);
@@ -1502,7 +1556,7 @@ static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)
for (i = 0; i < req->num_pages; i++)
__free_page(req->pages[i]);
- if (req->ff)
+ if (req->ff && !must_release_synchronously(req->ff))
fuse_file_put(req->ff, false);
}
@@ -1519,6 +1573,8 @@ static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
dec_zone_page_state(req->pages[i], NR_WRITEBACK_TEMP);
bdi_writeout_inc(bdi);
}
+ if (must_release_synchronously(req->ff))
+ __fuse_file_put(req->ff);
wake_up(&fi->page_waitq);
}
@@ -1659,8 +1715,13 @@ int fuse_write_inode(struct inode *inode, struct writeback_control *wbc)
ff = __fuse_write_file_get(fc, fi);
err = fuse_flush_times(inode, ff);
- if (ff)
- fuse_file_put(ff, 0);
+ if (ff) {
+ if (must_release_synchronously(ff)) {
+ __fuse_file_put(ff);
+ wake_up(&fi->page_waitq);
+ } else
+ fuse_file_put(ff, false);
+ }
return err;
}
--
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