ext2, ext4: only set S_DAX for regular inodes

When S_DAX is set on an inode we assume that if there are pages attached
to the mapping (mapping->nrpages != 0), those pages are clean zero pages
that were used to service reads from holes.  Any dirty data associated
with the inode should be in the form of DAX exceptional entries
(mapping->nrexceptional) that is written back via
dax_writeback_mapping_range().

With the current code, though, this isn't always true.  For example,
ext2 and ext4 directory inodes can have S_DAX set, but have their dirty
data stored as dirty page cache entries.  For these types of inodes,
having S_DAX set doesn't really make sense since their I/O doesn't
actually happen through the DAX code path.

Instead, only allow S_DAX to be set for regular inodes for ext2 and
ext4.  This allows us to have strict DAX vs non-DAX paths in the
writeback code.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 338eefda70c6fc4e2055c0165b590febf1295acb..27e2cdd4999b7791c1da784dcc7991fcffc50f67 100644 (file)
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -1296,7 +1296,7 @@ void ext2_set_inode_flags(struct inode *inode)
                inode->i_flags |= S_NOATIME;
        if (flags & EXT2_DIRSYNC_FL)
                inode->i_flags |= S_DIRSYNC;
-       if (test_opt(inode->i_sb, DAX))
+       if (test_opt(inode->i_sb, DAX) && S_ISREG(inode->i_mode))
                inode->i_flags |= S_DAX;
 }
 

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9cc57c3b466123f597dc28c6daed902faa7db081..5708e689e63dda679608f7bb262e824e31e78aa1 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4155,7 +4155,7 @@ void ext4_set_inode_flags(struct inode *inode)
                new_fl |= S_NOATIME;
        if (flags & EXT4_DIRSYNC_FL)
                new_fl |= S_DIRSYNC;
-       if (test_opt(inode->i_sb, DAX))
+       if (test_opt(inode->i_sb, DAX) && S_ISREG(inode->i_mode))
                new_fl |= S_DAX;
        inode_set_flags(inode, new_fl,
                        S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX);