Hi Christoph,
Thanks for your quick response!
On 11/20/2011 03:11 AM, Christoph Hellwig wrote:
> On Sat, Nov 19, 2011 at 04:37:13PM +0800, Jeff Liu wrote:
>>
>> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
>
> Thanks a lot Jeff. A few comments below:
>
>> +int
>> +xfs_seek_data_hole(
>> + struct xfs_inode *ip,
>> + loff_t *start,
>> + u32 type)
>> +{
>> + xfs_mount_t *mp = ip->i_mount;
>
> please use
>
> struct xfs_mount *mp = ip->i_mount;
>
> for all new code.
>
>> + if (xfs_get_extsz_hint(ip) ||
>> + ip->i_d.di_flags & (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)) {
>> + filelen = XFS_MAXIOFFSET(mp);
>> + } else {
>> + filelen = ip->i_size;
>> + }
>
> I don't understand this. XFS_MAXIOFFSET is the maximum possible file
> size in an XFS filesystem - using it with an extent size hint or
> the prealloc or appen only flags doesn't make sense to me.
Sorry, I forgot why I using it to retrieve the file size before. :( but
it definitely don't needed here.
>
>> + if (type == SEEK_DATA) {
>
> xfs_seek_data_hole shares almost no common code between the SEEK_DATA
> and SEEK_HOLE cases, which suggests it probably should be two different
> routines.
Yes, it's better to split SEEK_DATA/SEEK_HOLE into two different functions.
>
>
>> +STATIC loff_t
>> +xfs_file_llseek(
>> + struct file *file,
>> + loff_t offset,
>> + int origin)
>> +{
>> + struct inode *inode = file->f_mapping->host;
>> + int ret;
>> +
>> + if (origin != SEEK_DATA && origin != SEEK_HOLE)
>> + return generic_file_llseek(file, offset, origin);
>> +
>> + mutex_lock(&inode->i_mutex);
>> + switch (origin) {
>> + case SEEK_DATA:
>> + case SEEK_HOLE:
>
> Having the if above and then the switch here seems like and odd style.
> I'd do either an if, or a switch statement for all possible variants,
> but not both.
I'll fix it with switch statement then. :-)
>
>> + if (offset >= i_size_read(inode)) {
>> + ret = -ENXIO;
>> + goto error;
>> + }
>> +
>> + ret = xfs_find_desired_extent(inode, &offset, origin);
>> + if (ret)
>> + goto error;
>> + }
>> +
>> + if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {
>> + ret = -EINVAL;
>> + goto error;
>> + }
>
> I don't think this could ever happen on XFS.
>
>> + if (offset > inode->i_sb->s_maxbytes) {
>> + ret = -EINVAL;
>> + goto error;
>> + }
>
> This also shouldn't happen if the low-level code does the right
> thing.
>
>> + if (offset != file->f_pos) {
>> + file->f_pos = offset;
>> + file->f_version = 0;
>> + }
>
> XFS never uses f_version, no need to update it.
Thanks for pointing out my mistakes for above three issues,
I have not think carefully about them, just copy && paste the code block
from btrfs instead, they will be fixed in the next post.
>
>> +int
>> +xfs_find_desired_extent(
>> + struct inode *inode,
>> + loff_t *start,
>> + u32 type)
>
> I think this would better be merged with the code currenly in
> xfs_file_llseek. Maybe move all the SEEK_DATA/SEEK_HOLE specific
> code from there to this function?
>
> Also please move this routine to be next to xfs_file_llseek in xfs_file.c,
> which also means that it can be marked static.
ok, I'll merge both find_desired_extent() and seek_data_hole() to a
single routine and place it there.
>
>> +{
>> + xfs_inode_t *ip = XFS_I(inode);
>> + xfs_mount_t *mp = ip->i_mount;
>
> Just as above please use the struct versions for new code.
>
>> + /*
>> + * Flush the delay alloc blocks. Even after flushing the inode,
>> + * there can still be delalloc blocks on the inode beyond EOF
>> + * due to speculative preallocation. These are not removed until
>> + * the release function is called or the inode is inactivated.
>> + * Hence we cannot assert here that ip->i_delayed_blks == 0.
>> + */
>> + if (ip->i_delayed_blks || ip->i_size > ip->i_d.di_size) {
>> + error = xfs_flush_pages(ip, 0, -1, 0, FI_REMAPF);
>> + if (error)
>> + goto out_unlock_iolock;
>> + }
>
> For the final version we should get rid of this flush and instead look
> for pages having dirty unwritten extents in the pagecache and adjust
> the result based on it. I'm fine with delaying this until all other
> issues are sorted out.
Per Dave's comments, we would get ride of pages flush if using
xfs_bmapi_read() to retrieve the delayed extents info from the initial
implementation.
Thanks,
-Jeff
>
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