Commit 9ffbb916 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Linus Torvalds
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[PATCH] fuse: fix hang on SMP

Fuse didn't always call i_size_write() with i_mutex held which caused rare
hangs on SMP/32bit.  This bug has been present since fuse-2.2, well before
being merged into mainline.

The simplest solution is to protect i_size_write() with the per-connection
spinlock.  Using i_mutex for this purpose would require some restructuring of
the code and I'm not even sure it's always safe to acquire i_mutex in all
places i_size needs to be set.

Since most of vmtruncate is already duplicated for other reasons, duplicate
the remaining part as well, making all i_size_write() calls internal to fuse.

Using i_size_write() was unnecessary in fuse_init_inode(), since this function
is only called on a newly created locked inode.

Reported by a few people over the years, but special thanks to Dana Henriksen
who was persistent enough in helping me debug it.
Signed-off-by: default avatarMiklos Szeredi <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 48d1a7ea
......@@ -935,14 +935,30 @@ static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg)
static void fuse_vmtruncate(struct inode *inode, loff_t offset)
struct fuse_conn *fc = get_fuse_conn(inode);
int need_trunc;
need_trunc = inode->i_size > offset;
i_size_write(inode, offset);
if (need_trunc) {
struct address_space *mapping = inode->i_mapping;
unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
truncate_inode_pages(mapping, offset);
* Set attributes, and at the same time refresh them.
* Truncation is slightly complicated, because the 'truncate' request
* may fail, in which case we don't want to touch the mapping.
* vmtruncate() doesn't allow for this case. So do the rlimit
* checking by hand and call vmtruncate() only after the file has
* actually been truncated.
* vmtruncate() doesn't allow for this case, so do the rlimit checking
* and the actual truncation by hand.
static int fuse_setattr(struct dentry *entry, struct iattr *attr)
......@@ -993,12 +1009,8 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr)
err = -EIO;
} else {
if (is_truncate) {
loff_t origsize = i_size_read(inode);
i_size_write(inode, outarg.attr.size);
if (origsize > outarg.attr.size)
vmtruncate(inode, outarg.attr.size);
if (is_truncate)
fuse_vmtruncate(inode, outarg.attr.size);
fuse_change_attributes(inode, &outarg.attr);
fi->i_time = time_to_jiffies(outarg.attr_valid,
......@@ -481,8 +481,10 @@ static int fuse_commit_write(struct file *file, struct page *page,
err = -EIO;
if (!err) {
pos += count;
if (pos > i_size_read(inode))
if (pos > inode->i_size)
i_size_write(inode, pos);
if (offset == 0 && to == PAGE_CACHE_SIZE) {
......@@ -586,8 +588,12 @@ static ssize_t fuse_direct_io(struct file *file, const char __user *buf,
fuse_put_request(fc, req);
if (res > 0) {
if (write && pos > i_size_read(inode))
i_size_write(inode, pos);
if (write) {
if (pos > inode->i_size)
i_size_write(inode, pos);
*ppos = pos;
......@@ -109,6 +109,7 @@ static int fuse_remount_fs(struct super_block *sb, int *flags, char *data)
void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr)
struct fuse_conn *fc = get_fuse_conn(inode);
if (S_ISREG(inode->i_mode) && i_size_read(inode) != attr->size)
......@@ -117,7 +118,9 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr)
inode->i_nlink = attr->nlink;
inode->i_uid = attr->uid;
inode->i_gid = attr->gid;
i_size_write(inode, attr->size);
inode->i_blocks = attr->blocks;
inode->i_atime.tv_sec = attr->atime;
inode->i_atime.tv_nsec = attr->atimensec;
......@@ -130,7 +133,7 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr)
static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
inode->i_mode = attr->mode & S_IFMT;
i_size_write(inode, attr->size);
inode->i_size = attr->size;
if (S_ISREG(inode->i_mode)) {
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