[Devel] [PATCH 06/14] fuse: Trust kernel i_size only - v3
Maxim V. Patlasov
MPatlasov at parallels.com
Mon Apr 1 03:41:33 PDT 2013
Make fuse think that when writeback is on the inode's i_size is always
up-to-date and not update it with the value received from the userspace.
This is done because the page cache code may update i_size without letting
the FS know.
This assumption implies fixing the previously introduced short-read helper --
when a short read occurs the 'hole' is filled with zeroes.
fuse_file_fallocate() is also fixed because now we should keep i_size up to
date, so it must be updated if FUSE_FALLOCATE request succeeded.
Changed in v2:
- improved comment in fuse_short_read()
- fixed fuse_file_fallocate() for KEEP_SIZE mode
Changed in v3:
- fixed fuse_fillattr() not to use local i_size if writeback-cache is off
- added a comment explaining why we cannot trust attr.size from server
Original patch by: Pavel Emelyanov <xemul at openvz.org>
Signed-off-by: Maxim V. Patlasov <MPatlasov at parallels.com>
---
fs/fuse/dir.c | 13 +++++++++++--
fs/fuse/file.c | 43 +++++++++++++++++++++++++++++++++++++++++--
fs/fuse/inode.c | 11 +++++++++--
3 files changed, 61 insertions(+), 6 deletions(-)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 8506522..8672ee4 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -845,6 +845,11 @@ static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
struct kstat *stat)
{
unsigned int blkbits;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+
+ /* see the comment in fuse_change_attributes() */
+ if (fc->writeback_cache && S_ISREG(inode->i_mode))
+ attr->size = i_size_read(inode);
stat->dev = inode->i_sb->s_dev;
stat->ino = attr->ino;
@@ -1571,6 +1576,7 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
struct fuse_setattr_in inarg;
struct fuse_attr_out outarg;
bool is_truncate = false;
+ bool is_wb = fc->writeback_cache;
loff_t oldsize;
int err;
@@ -1643,7 +1649,9 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
fuse_change_attributes_common(inode, &outarg.attr,
attr_timeout(&outarg));
oldsize = inode->i_size;
- i_size_write(inode, outarg.attr.size);
+ /* see the comment in fuse_change_attributes() */
+ if (!is_wb || is_truncate || !S_ISREG(inode->i_mode))
+ i_size_write(inode, outarg.attr.size);
if (is_truncate) {
/* NOTE: this may release/reacquire fc->lock */
@@ -1655,7 +1663,8 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
* Only call invalidate_inode_pages2() after removing
* FUSE_NOWRITE, otherwise fuse_launder_page() would deadlock.
*/
- if (S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
+ if ((is_truncate || !is_wb) &&
+ S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
truncate_pagecache(inode, oldsize, outarg.attr.size);
invalidate_inode_pages2(inode->i_mapping);
}
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index ee44b24..af58bbf 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/compat.h>
#include <linux/swap.h>
+#include <linux/falloc.h>
static const struct file_operations fuse_direct_io_file_operations;
@@ -543,9 +544,31 @@ static void fuse_short_read(struct fuse_req *req, struct inode *inode,
u64 attr_ver)
{
size_t num_read = req->out.args[0].size;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+
+ if (fc->writeback_cache) {
+ /*
+ * A hole in a file. Some data after the hole are in page cache,
+ * but have not reached the client fs yet. So, the hole is not
+ * present there.
+ */
+ int i;
+ int start_idx = num_read >> PAGE_CACHE_SHIFT;
+ size_t off = num_read & (PAGE_CACHE_SIZE - 1);
- loff_t pos = page_offset(req->pages[0]) + num_read;
- fuse_read_update_size(inode, pos, attr_ver);
+ for (i = start_idx; i < req->num_pages; i++) {
+ struct page *page = req->pages[i];
+ void *mapaddr = kmap_atomic(page);
+
+ memset(mapaddr + off, 0, PAGE_CACHE_SIZE - off);
+
+ kunmap_atomic(mapaddr);
+ off = 0;
+ }
+ } else {
+ loff_t pos = page_offset(req->pages[0]) + num_read;
+ fuse_read_update_size(inode, pos, attr_ver);
+ }
}
static int fuse_readpage(struct file *file, struct page *page)
@@ -2286,6 +2309,8 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
.mode = mode
};
int err;
+ bool change_i_size = fc->writeback_cache &&
+ !(mode & FALLOC_FL_KEEP_SIZE);
if (fc->no_fallocate)
return -EOPNOTSUPP;
@@ -2294,6 +2319,11 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
if (IS_ERR(req))
return PTR_ERR(req);
+ if (change_i_size) {
+ struct inode *inode = file->f_mapping->host;
+ mutex_lock(&inode->i_mutex);
+ }
+
req->in.h.opcode = FUSE_FALLOCATE;
req->in.h.nodeid = ff->nodeid;
req->in.numargs = 1;
@@ -2307,6 +2337,15 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
}
fuse_put_request(fc, req);
+ if (change_i_size) {
+ struct inode *inode = file->f_mapping->host;
+
+ if (!err)
+ fuse_write_update_size(inode, offset + length);
+
+ mutex_unlock(&inode->i_mutex);
+ }
+
return err;
}
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 01353ed..94319e6 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -197,6 +197,7 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
{
struct fuse_conn *fc = get_fuse_conn(inode);
struct fuse_inode *fi = get_fuse_inode(inode);
+ bool is_wb = fc->writeback_cache;
loff_t oldsize;
struct timespec old_mtime;
@@ -210,10 +211,16 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
fuse_change_attributes_common(inode, attr, attr_valid);
oldsize = inode->i_size;
- i_size_write(inode, attr->size);
+ /*
+ * In case of writeback_cache enabled, the cached writes beyond EOF
+ * extend local i_size without keeping userspace server in sync. So,
+ * attr->size coming from server can be stale. We cannot trust it.
+ */
+ if (!is_wb || !S_ISREG(inode->i_mode))
+ i_size_write(inode, attr->size);
spin_unlock(&fc->lock);
- if (S_ISREG(inode->i_mode)) {
+ if (!is_wb && S_ISREG(inode->i_mode)) {
bool inval = false;
if (oldsize != attr->size) {
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