[PATCH 5.10 016/157] zonefs: Fix O_APPEND async write handling

Greg Kroah-Hartman
2021-03-22T12:41:24Z

From: Damien Le Moal <damien.lemoal@wdc.com>

commit ebfd68cd0c1e81267c757332385cb96df30dacce upstream.

zonefs updates the size of a sequential zone file inode only on
completion of direct writes. When executing asynchronous append writes
(with a file open with O_APPEND or using RWF_APPEND), the use of the
current inode size in generic_write_checks() to set an iocb offset thus
leads to unaligned write if an application issues an append write
operation with another write already being executed.

Fix this problem by introducing zonefs_write_checks() as a modified
version of generic_write_checks() using the file inode wp_offset for an
append write iocb offset. Also introduce zonefs_write_check_limits() to
replace generic_write_check_limits() call. This zonefs special helper
makes sure that the maximum file limit used is the maximum size of the
file being accessed.

Since zonefs_write_checks() already truncates the iov_iter, the calls
to iov_iter_truncate() in zonefs_file_dio_write() and
zonefs_file_buffered_write() are removed.

Fixes: 8dcc1a9d90c1 ("fs: New zonefs file system")
Cc: <stable@vger.kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/zonefs/super.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 68 insertions(+), 10 deletions(-)

--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -720,6 +720,68 @@ out_release:
}

/*
+ * Do not exceed the LFS limits nor the file zone size. If pos is under the
+ * limit it becomes a short access. If it exceeds the limit, return -EFBIG.
+ */
+static loff_t zonefs_write_check_limits(struct file *file, loff_t pos,
+ loff_t count)
+{
+ struct inode *inode = file_inode(file);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ loff_t limit = rlimit(RLIMIT_FSIZE);
+ loff_t max_size = zi->i_max_size;
+
+ if (limit != RLIM_INFINITY) {
+ if (pos >= limit) {
+ send_sig(SIGXFSZ, current, 0);
+ return -EFBIG;
+ }
+ count = min(count, limit - pos);
+ }
+
+ if (!(file->f_flags & O_LARGEFILE))
+ max_size = min_t(loff_t, MAX_NON_LFS, max_size);
+
+ if (unlikely(pos >= max_size))
+ return -EFBIG;
+
+ return min(count, max_size - pos);
+}
+
+static ssize_t zonefs_write_checks(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file_inode(file);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ loff_t count;
+
+ if (IS_SWAPFILE(inode))
+ return -ETXTBSY;
+
+ if (!iov_iter_count(from))
+ return 0;
+
+ if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
+ return -EINVAL;
+
+ if (iocb->ki_flags & IOCB_APPEND) {
+ if (zi->i_ztype != ZONEFS_ZTYPE_SEQ)
+ return -EINVAL;
+ mutex_lock(&zi->i_truncate_mutex);
+ iocb->ki_pos = zi->i_wpoffset;
+ mutex_unlock(&zi->i_truncate_mutex);
+ }
+
+ count = zonefs_write_check_limits(file, iocb->ki_pos,
+ iov_iter_count(from));
+ if (count < 0)
+ return count;
+
+ iov_iter_truncate(from, count);
+ return iov_iter_count(from);
+}
+
+/*
* Handle direct writes. For sequential zone files, this is the only possible
* write path. For these files, check that the user is issuing writes
* sequentially from the end of the file. This code assumes that the block layer
@@ -736,8 +798,7 @@ static ssize_t zonefs_file_dio_write(str
struct super_block *sb = inode->i_sb;
bool sync = is_sync_kiocb(iocb);
bool append = false;
- size_t count;
- ssize_t ret;
+ ssize_t ret, count;

/*
* For async direct IOs to sequential zone files, refuse IOCB_NOWAIT
@@ -755,12 +816,11 @@ static ssize_t zonefs_file_dio_write(str
inode_lock(inode);
}

- ret = generic_write_checks(iocb, from);
- if (ret <= 0)
+ count = zonefs_write_checks(iocb, from);
+ if (count <= 0) {
+ ret = count;
goto inode_unlock;
-
- iov_iter_truncate(from, zi->i_max_size - iocb->ki_pos);
- count = iov_iter_count(from);
+ }

if ((iocb->ki_pos | count) & (sb->s_blocksize - 1)) {
ret = -EINVAL;
@@ -820,12 +880,10 @@ static ssize_t zonefs_file_buffered_writ
inode_lock(inode);
}

- ret = generic_write_checks(iocb, from);
+ ret = zonefs_write_checks(iocb, from);
if (ret <= 0)
goto inode_unlock;

- iov_iter_truncate(from, zi->i_max_size - iocb->ki_pos);
-
ret = iomap_file_buffered_write(iocb, from, &zonefs_iomap_ops);
if (ret > 0)
iocb->ki_pos += ret;