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 <chan...@linux.vnet.ibm.com>
---
fs/btrfs/file.c | 12 ++++++++++--
fs/btrfs/inode.c | 2 +-
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index f69e030..aba215c 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1755,6 +1755,8 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
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);
@@ -1793,14 +1795,17 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
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)
@@ -1812,6 +1817,9 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
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);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ea7d9f1..0a8a5ff 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4824,7 +4824,6 @@ static int btrfs_setsize(struct inode *inode, struct
iattr *attr)
}
if (newsize > oldsize) {
- truncate_pagecache(inode, newsize);
/*
* Don't do an expanding truncate while snapshoting is ongoing.
* This is to ensure the snapshot captures a fully consistent
@@ -4847,6 +4846,7 @@ static int btrfs_setsize(struct inode *inode, struct
iattr *attr)
i_size_write(inode, newsize);
btrfs_ordered_update_i_size(inode, i_size_read(inode), NULL);
+ pagecache_isize_extended(inode, oldsize, newsize);
ret = btrfs_update_inode(trans, root, inode);
btrfs_end_write_no_snapshoting(root);
btrfs_end_transaction(trans, root);
--
2.1.0
--
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