Btrfs: Clean pte corresponding to page straddling i_size
When extending a file by either "truncate up" or by writing beyond i_size, the
page which had i_size needs to be marked "read only" so that future writes to
the page via mmap interface causes btrfs_page_mkwrite() to be invoked. If not,
a write performed after extending the file via the mmap interface will find
the page to be writaeable and continue writing to the page without invoking
btrfs_page_mkwrite() i.e. we end up writing to a file without reserving disk
space.
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 58bb297..953f0ad 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1778,6 +1778,8 @@
ssize_t err;
loff_t pos;
size_t count;
+ loff_t oldsize;
+ int clean_page = 0;
mutex_lock(&inode->i_mutex);
err = generic_write_checks(iocb, from);
@@ -1816,14 +1818,17 @@
pos = iocb->ki_pos;
count = iov_iter_count(from);
start_pos = round_down(pos, root->sectorsize);
- if (start_pos > i_size_read(inode)) {
+ oldsize = i_size_read(inode);
+ if (start_pos > oldsize) {
/* Expand hole size to cover write data, preventing empty gap */
end_pos = round_up(pos + count, root->sectorsize);
- err = btrfs_cont_expand(inode, i_size_read(inode), end_pos);
+ err = btrfs_cont_expand(inode, oldsize, end_pos);
if (err) {
mutex_unlock(&inode->i_mutex);
goto out;
}
+ if (start_pos > round_up(oldsize, root->sectorsize))
+ clean_page = 1;
}
if (sync)
@@ -1835,6 +1840,9 @@
num_written = __btrfs_buffered_write(file, from, pos);
if (num_written > 0)
iocb->ki_pos = pos + num_written;
+ if (clean_page)
+ pagecache_isize_extended(inode, oldsize,
+ i_size_read(inode));
}
mutex_unlock(&inode->i_mutex);