| Message ID | 1462494596-20938-5-git-send-email-toshi.kani@hpe.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Not really for the patch, but given that we have the right people on CC: Do we really want to keep DAX support in ext2 in the long run? ext2 is missing a lot of the useful features for a modern FS, shouldn't we direct people to use ext4 (in non-journal mode if needed) if they want to use DAX? ext4 will even support the unmodified ext2 fs, so it shouldn't be a big hurdle, and it would avoid a lot of churn in ext2.
On Sun 08-05-16 01:59:37, Christoph Hellwig wrote: > Not really for the patch, but given that we have the right people > on CC: > > Do we really want to keep DAX support in ext2 in the long run? ext2 > is missing a lot of the useful features for a modern FS, shouldn't > we direct people to use ext4 (in non-journal mode if needed) if they > want to use DAX? ext4 will even support the unmodified ext2 fs, so it > shouldn't be a big hurdle, and it would avoid a lot of churn in ext2. I've heard concerns that embedded people use ext2 driver (due to smaller code size than ext4 - 1.7 MB object for ext2 vs over 7 MB object for ext4 in my build) including old XIP support. DAX has replaced the old XIP code so removing DAX from ext2 would be a regression for them - either they'd have to go with significantly larger module or without XIP. So for now I'd leave DAX in ext2. Honza
On Thu 05-05-16 18:29:55, Toshi Kani wrote: > When a partition is not aligned by 4KB, mount -o dax succeeds, > but any read/write access to the filesystem fails, except for > metadata update. > > Call bdev_supports_dax() to perform proper precondition checks > which includes this partition alignment check. > > Signed-off-by: Toshi Kani <toshi.kani@hpe.com> > Cc: Jan Kara <jack@suse.cz> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Ross Zwisler <ross.zwisler@linux.intel.com> > Cc: Christoph Hellwig <hch@infradead.org> > Cc: Boaz Harrosh <boaz@plexistor.com> Looks good to me. Since this patch depends on the first two in your series, just feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> and merge it along with other patches. I've removed the ext2 patch from the previous version from my tree. Honza
diff --git a/fs/ext2/super.c b/fs/ext2/super.c index b78caf2..7d63de4 100644 --- a/fs/ext2/super.c +++ b/fs/ext2/super.c @@ -922,16 +922,9 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent) blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size); if (sbi->s_mount_opt & EXT2_MOUNT_DAX) { - if (blocksize != PAGE_SIZE) { - ext2_msg(sb, KERN_ERR, - "error: unsupported blocksize for dax"); + err = bdev_supports_dax(sb, blocksize); + if (err) goto failed_mount; - } - if (!sb->s_bdev->bd_disk->fops->direct_access) { - ext2_msg(sb, KERN_ERR, - "error: device does not support dax"); - goto failed_mount; - } } /* If the blocksize doesn't match, re-read the thing.. */
When a partition is not aligned by 4KB, mount -o dax succeeds, but any read/write access to the filesystem fails, except for metadata update. Call bdev_supports_dax() to perform proper precondition checks which includes this partition alignment check. Signed-off-by: Toshi Kani <toshi.kani@hpe.com> Cc: Jan Kara <jack@suse.cz> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Boaz Harrosh <boaz@plexistor.com> --- fs/ext2/super.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-)