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: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
Signed-off-by: Amit Sahrawat <a.sahrawat@xxxxxxxxxxx>
---
fs/fat/fat.h | 1 +
fs/fat/file.c | 3 +++
fs/fat/inode.c | 12 ++++++++++++
3 files changed, 16 insertions(+)
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index eff027d..61801da 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -374,6 +374,7 @@ 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);
diff --git a/fs/fat/file.c b/fs/fat/file.c
index f2c73ae..757fc20 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -523,6 +523,9 @@ 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;
down_write(&MSDOS_I(inode)->truncate_lock);
truncate_setsize(inode, attr->ia_size);
fat_truncate_blocks(inode, attr->ia_size);
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index f362796..9bf44eb 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -339,6 +339,18 @@ 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,
--
1.7.11-rc0
--
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