From: Jeff Layton <jlayton@xxxxxxxxxx>
sb->s_maxbytes is supposed to indicate the maximum size of a file that can
exist on the filesystem. It's declared as an unsigned long long.
Even if a filesystem has no inherent limit that prevents it from using
every bit in that unsigned long long, it's still problematic to set it to
anything larger than MAX_LFS_FILESIZE. There are places in the kernel
that cast s_maxbytes to a signed value. If it's set too large then this
cast makes it a negative number and generally breaks the comparison.
Change s_maxbytes to be loff_t instead. That should help eliminate the
temptation to set it too large by making it a signed value.
Also, add a warning for couple of releases to help catch filesystems that
set s_maxbytes too large. Eventually we can either convert this to a
BUG() or just remove it and in the hope that no one will get it wrong now
that it's a signed value.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Robert Love <rlove@xxxxxxxxxx>
Cc: Mandeep Singh Baines <msb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/super.c | 10 ++++++++++
include/linux/fs.h | 2 +-
2 files changed, 11 insertions(+), 1 deletion(-)
diff -puN fs/super.c~vfs-change-sb-s_maxbytes-to-a-loff_t fs/super.c
--- a/fs/super.c~vfs-change-sb-s_maxbytes-to-a-loff_t
+++ a/fs/super.c
@@ -893,6 +893,16 @@ vfs_kern_mount(struct file_system_type *
if (error)
goto out_sb;
+ /*
+ * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
+ * but s_maxbytes was an unsigned long long for many releases. Throw
+ * this warning for a little while to try and catch filesystems that
+ * violate this rule. This warning should be either removed or
+ * converted to a BUG() in 2.6.34.
+ */
+ WARN((mnt->mnt_sb->s_maxbytes < 0), "WARNING: %s set sb->s_maxbytes to "
+ "negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes);
+
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
up_write(&mnt->mnt_sb->s_umount);
diff -puN include/linux/fs.h~vfs-change-sb-s_maxbytes-to-a-loff_t include/linux/fs.h
--- a/include/linux/fs.h~vfs-change-sb-s_maxbytes-to-a-loff_t
+++ a/include/linux/fs.h
@@ -1316,7 +1316,7 @@ struct super_block {
unsigned long s_blocksize;
unsigned char s_blocksize_bits;
unsigned char s_dirt;
- unsigned long long s_maxbytes; /* Max file size */
+ loff_t s_maxbytes; /* Max file size */
struct file_system_type *s_type;
const struct super_operations *s_op;
struct dquot_operations *dq_op;
_
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
