Commit c0ef0cc9 authored by Namjae Jeon's avatar Namjae Jeon Committed by Linus Torvalds

fat: fix data past EOF resulting from fsx testsuite

When running FSX with direct I/O mode, fsx resulted in DATA past EOF issues.

  fsx ./file2 -Z -r 4096 -w 4096
  truncating to largest ever: 0x907c
  fallocating to largest ever: 0x11137
  truncating to largest ever: 0x2c6fe
  truncating to largest ever: 0x2cfdf
  fallocating to largest ever: 0x40000
  Mapped Read: non-zero data past EOF (0x18628) page offset 0x629 is 0x2a4e

The reason being, it is doing a truncate down, but the zeroing does not
happen on the last block boundary when offset is not aligned.  Even though
it calls truncate_setsize()->truncate_inode_pages()->
truncate_inode_pages_range() and considers the partial zeroout but it
retrieves the page using find_lock_page() - which only looks the page in
the cache.  So, zeroing out does not happen in case of direct IO.

Make a truncate page based around block_truncate_page for FAT filesystem
and invoke that helper to zerout in case the offset is not aligned with
the blocksize.
Signed-off-by: default avatarNamjae Jeon <>
Signed-off-by: default avatarAmit Sahrawat <>
Acked-by: default avatarOGAWA Hirofumi <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent f441ada0
......@@ -370,6 +370,7 @@ extern int fat_file_fsync(struct file *file, loff_t start, loff_t end,
int datasync);
/* fat/inode.c */
extern int fat_block_truncate_page(struct inode *inode, loff_t from);
extern void fat_attach(struct inode *inode, loff_t i_pos);
extern void fat_detach(struct inode *inode);
extern struct inode *fat_iget(struct super_block *sb, loff_t i_pos);
......@@ -443,6 +443,9 @@ int fat_setattr(struct dentry *dentry, struct iattr *attr)
if (attr->ia_valid & ATTR_SIZE) {
error = fat_block_truncate_page(inode, attr->ia_size);
if (error)
goto out;
truncate_setsize(inode, attr->ia_size);
fat_truncate_blocks(inode, attr->ia_size);
......@@ -294,6 +294,18 @@ static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
return blocknr;
* fat_block_truncate_page() zeroes out a mapping from file offset `from'
* up to the end of the block which corresponds to `from'.
* This is required during truncate to physically zeroout the tail end
* of that block so it doesn't yield old data if the file is later grown.
* Also, avoid causing failure from fsx for cases of "data past EOF"
int fat_block_truncate_page(struct inode *inode, loff_t from)
return block_truncate_page(inode->i_mapping, from, fat_get_block);
static const struct address_space_operations fat_aops = {
.readpage = fat_readpage,
.readpages = fat_readpages,
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