* [PATCH v3 2/2] f2fs: fix to zero post-EOF data when extending file size
2026-08-07 13:06 [PATCH v3 1/2] f2fs: fix to off-by-one issue in f2fs_zero_post_eof_page() Chao Yu
@ 2026-08-07 13:06 ` Chao Yu
0 siblings, 0 replies; 2+ messages in thread
From: Chao Yu @ 2026-08-07 13:06 UTC (permalink / raw)
To: jaegeuk; +Cc: linux-f2fs-devel, linux-kernel, Chao Yu, stable
generic/794 4s ... - output mismatch (see /share/git/fstests/results//generic/794.out.bad)
--- tests/generic/794.out 2026-06-12 08:46:32.766426241 +0800
+++ /share/git/fstests/results//generic/794.out.bad 2026-07-05 18:32:55.000000000 +0800
@@ -1,4 +1,16 @@
QA output created by 794
append_write
+FAIL: non-zero data in gap [4080,4096) after shutdown+remount
+000000 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a >ZZZZZZZZZZZZZZZZ<
+*
+001000
truncate_up
...
(Run 'diff -u /share/git/fstests/tests/generic/794.out /share/git/fstests/results//generic/794.out.bad' to see the entire diff)
Ran: generic/794
Failures: generic/794
Failed 1 of 1 tests
Steps of generic/794:
1. write 4096 bytes to file w/ 0x5a
2. use fiemap to get PBA of first block in file
3. truncate file to 4080
4. umount; write 4096 bytes to file w/ 0x5a directly via PBA; mount
5. extend filesize via
a) append 4096 from offset 4096, or
b) truncate 8192, or
c) fallocate 4096 from offset 4096
6. verify the gap is zeroed in memory [4080,4096)
7. sync range 4096 from offset 4096; shutdown -f (flush meta before shutdown)
8. umount; mount; verify [4080,4096) is zeroed or not.
When extending file size (e.g. via truncate, fallocate, or write) across an
unaligned EOF boundary, we need to ensure that post-EOF data in the partial
page is zeroed out in pagecache and marked dirty, meanwhile, tagging the inode
with FI_ZERO_POST_EOF, so that following checkpoint() and fsync() can persist
the page contain zeroed data before committing inode w/ updated i_size.
This help to prevent stale disk data beyond the previous EOF from being exposed
after remounting or crash recovery.
Since f2fs is a LFS filesystem, we only support direct write via PBA in pinfile,
and pinfile has section-aligned filesize, so in Android, there should no problem,
but for other usage in different environment, let's fix this w/ fsync_mode=strict
mount option.
Cc: stable@kernel.org
Signed-off-by: Chao Yu <chao@kernel.org>
---
v3:
- persist post eof data in f2fs_zero_post_eof_page()
fs/f2fs/file.c | 100 +++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 84 insertions(+), 16 deletions(-)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 9dbe509926b2..efa06aef3077 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -36,16 +36,52 @@
#include <trace/events/f2fs.h>
#include <uapi/linux/f2fs.h>
-static void f2fs_zero_post_eof_page(struct inode *inode,
- loff_t new_size, bool lock)
+static int fill_zero(struct inode *inode, pgoff_t index,
+ loff_t start, loff_t len);
+
+static int do_zero_post_eof_page(struct inode *inode, loff_t new_size)
+{
+ loff_t old_size = i_size_read(inode);
+ unsigned int offset, len;
+ pgoff_t index;
+ int err;
+
+ offset = old_size & (PAGE_SIZE - 1);
+
+ if (!offset)
+ return 0;
+
+ len = min_t(loff_t, PAGE_SIZE - offset, new_size - old_size);
+ index = old_size >> PAGE_SHIFT;
+
+ if (f2fs_has_inline_data(inode)) {
+ /* data post eof should be always zero */
+ if (new_size <= MAX_INLINE_DATA(inode))
+ return 0;
+ err = f2fs_convert_inline_inode(inode);
+ if (err)
+ return err;
+ }
+
+ err = fill_zero(inode, index, offset, len);
+ if (err)
+ return err;
+ return filemap_write_and_wait_range(inode->i_mapping,
+ old_size, old_size + len - 1);
+}
+
+static int f2fs_zero_post_eof_page(struct inode *inode,
+ loff_t new_size, bool lock, bool writeback)
{
loff_t old_size = i_size_read(inode);
+ bool strict =
+ F2FS_OPTION(F2FS_I_SB(inode)).fsync_mode == FSYNC_MODE_STRICT;
if (old_size >= new_size)
- return;
+ return 0;
- if (mapping_empty(inode->i_mapping))
- return;
+ if (!strict && mapping_empty(inode->i_mapping))
+ return 0;
if (lock)
filemap_invalidate_lock(inode->i_mapping);
@@ -53,6 +89,16 @@ static void f2fs_zero_post_eof_page(struct inode *inode,
truncate_inode_pages_range(inode->i_mapping, old_size, new_size - 1);
if (lock)
filemap_invalidate_unlock(inode->i_mapping);
+
+ if (!writeback || !strict)
+ return 0;
+ /*
+ * In fsync_mode=strict, when we expand an unaligned EOF size, we
+ * should zero post EOF data and writeback the data immediately,
+ * so that it can avoid exposing stale data after metadata flush
+ * and POR.
+ */
+ return do_zero_post_eof_page(inode, new_size);
}
static vm_fault_t f2fs_filemap_fault(struct vm_fault *vmf)
@@ -132,7 +178,10 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
f2fs_bug_on(sbi, f2fs_has_inline_data(inode));
- f2fs_zero_post_eof_page(inode, (folio->index + 1) << PAGE_SHIFT, true);
+ ret = f2fs_zero_post_eof_page(inode,
+ (folio->index + 1) << PAGE_SHIFT, true, false);
+ if (ret)
+ goto out_pagefault;
file_update_time(vmf->vma->vm_file);
filemap_invalidate_lock_shared(inode->i_mapping);
@@ -189,7 +238,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
out_sem:
filemap_invalidate_unlock_shared(inode->i_mapping);
-
+out_pagefault:
sb_end_pagefault(inode->i_sb);
out:
ret = vmf_fs_error(err);
@@ -1182,8 +1231,12 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
f2fs_down_write(&fi->i_gc_rwsem[WRITE]);
filemap_invalidate_lock(inode->i_mapping);
- if (attr->ia_size > old_size)
- f2fs_zero_post_eof_page(inode, attr->ia_size, false);
+ if (attr->ia_size > old_size) {
+ err = f2fs_zero_post_eof_page(inode,
+ attr->ia_size, false, true);
+ if (err)
+ goto err_out;
+ }
truncate_setsize(inode, attr->ia_size);
if (attr->ia_size <= old_size)
@@ -1192,6 +1245,7 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
* do not trim all blocks after i_size if target size is
* larger than i_size.
*/
+err_out:
filemap_invalidate_unlock(inode->i_mapping);
f2fs_up_write(&fi->i_gc_rwsem[WRITE]);
if (err)
@@ -1303,7 +1357,9 @@ static int f2fs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
if (ret)
return ret;
- f2fs_zero_post_eof_page(inode, offset + len, true);
+ ret = f2fs_zero_post_eof_page(inode, offset + len, true, false);
+ if (ret)
+ return ret;
pg_start = ((unsigned long long) offset) >> PAGE_SHIFT;
pg_end = ((unsigned long long) offset + len) >> PAGE_SHIFT;
@@ -1590,7 +1646,9 @@ static int f2fs_do_collapse(struct inode *inode, loff_t offset, loff_t len)
f2fs_down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
filemap_invalidate_lock(inode->i_mapping);
- f2fs_zero_post_eof_page(inode, offset + len, false);
+ ret = f2fs_zero_post_eof_page(inode, offset + len, false, false);
+ if (ret)
+ goto out_unlock;
f2fs_lock_op(sbi, &lc);
f2fs_drop_extent_tree(inode);
@@ -1598,6 +1656,7 @@ static int f2fs_do_collapse(struct inode *inode, loff_t offset, loff_t len)
ret = __exchange_data_block(inode, inode, end, start, nrpages - end, true);
f2fs_unlock_op(sbi, &lc);
+out_unlock:
filemap_invalidate_unlock(inode->i_mapping);
f2fs_up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
return ret;
@@ -1719,7 +1778,9 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
if (ret)
return ret;
- f2fs_zero_post_eof_page(inode, offset + len, true);
+ ret = f2fs_zero_post_eof_page(inode, offset + len, true, false);
+ if (ret)
+ return ret;
pg_start = ((unsigned long long) offset) >> PAGE_SHIFT;
pg_end = ((unsigned long long) offset + len) >> PAGE_SHIFT;
@@ -1854,7 +1915,9 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
f2fs_down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
filemap_invalidate_lock(mapping);
- f2fs_zero_post_eof_page(inode, offset + len, false);
+ ret = f2fs_zero_post_eof_page(inode, offset + len, false, false);
+ if (ret)
+ goto out_unlock;
truncate_pagecache(inode, offset);
while (!ret && idx > pg_start) {
@@ -1872,6 +1935,7 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
idx + delta, nr, false);
f2fs_unlock_op(sbi, &lc);
}
+out_unlock:
filemap_invalidate_unlock(mapping);
f2fs_up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
if (ret)
@@ -1914,7 +1978,9 @@ static int f2fs_expand_inode_data(struct inode *inode, loff_t offset,
if (err)
return err;
- f2fs_zero_post_eof_page(inode, offset + len, true);
+ err = f2fs_zero_post_eof_page(inode, offset + len, true, true);
+ if (err)
+ return err;
f2fs_balance_fs(sbi, true);
@@ -5285,8 +5351,10 @@ static ssize_t f2fs_write_checks(struct kiocb *iocb, struct iov_iter *from)
if (err)
return err;
- f2fs_zero_post_eof_page(inode,
- iocb->ki_pos + iov_iter_count(from), true);
+ err = f2fs_zero_post_eof_page(inode,
+ iocb->ki_pos + iov_iter_count(from), true, true);
+ if (err)
+ return err;
return count;
}
--
2.49.0
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