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fuse: fix the ->direct_IO() treatment of iov_iter 

the callers rely upon having any iov_iter_truncate() done inside
->direct_IO() countered by iov_iter_reexpand().

Reported-by: Qian Cai <cai@redhat.com>
Tested-by: Qian Cai <cai@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-09-17 17:26:56 -04:00
parent ffbc3dd197
commit 933a3752ba
1 changed files with 12 additions and 13 deletions
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25
fs/fuse/file.c
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@ -3091,11 +3091,10 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
ssize_t ret = 0;
struct file *file = iocb->ki_filp;
struct fuse_file *ff = file->private_data;
bool async_dio = ff->fc->async_dio;
loff_t pos = 0;
struct inode *inode;
loff_t i_size;
size_t count = iov_iter_count(iter);
size_t count = iov_iter_count(iter), shortened = 0;
loff_t offset = iocb->ki_pos;
struct fuse_io_priv *io;
@ -3103,17 +3102,9 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
inode = file->f_mapping->host;
i_size = i_size_read(inode);
if ((iov_iter_rw(iter) == READ) && (offset > i_size))
if ((iov_iter_rw(iter) == READ) && (offset >= i_size))
return 0;
/* optimization for short read */
if (async_dio && iov_iter_rw(iter) != WRITE && offset + count > i_size) {
if (offset >= i_size)
return 0;
iov_iter_truncate(iter, fuse_round_up(ff->fc, i_size - offset));
count = iov_iter_count(iter);
}
io = kmalloc(sizeof(struct fuse_io_priv), GFP_KERNEL);
if (!io)
return -ENOMEM;
@ -3129,15 +3120,22 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
* By default, we want to optimize all I/Os with async request
* submission to the client filesystem if supported.
*/
io->async = async_dio;
io->async = ff->fc->async_dio;
io->iocb = iocb;
io->blocking = is_sync_kiocb(iocb);
/* optimization for short read */
if (io->async && !io->write && offset + count > i_size) {
iov_iter_truncate(iter, fuse_round_up(ff->fc, i_size - offset));
shortened = count - iov_iter_count(iter);
count -= shortened;
}
/*
* We cannot asynchronously extend the size of a file.
* In such case the aio will behave exactly like sync io.
*/
if ((offset + count > i_size) && iov_iter_rw(iter) == WRITE)
if ((offset + count > i_size) && io->write)
io->blocking = true;
if (io->async && io->blocking) {
@ -3155,6 +3153,7 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
} else {
ret = __fuse_direct_read(io, iter, &pos);
}
iov_iter_reexpand(iter, iov_iter_count(iter) + shortened);
if (io->async) {
bool blocking = io->blocking;