Re: [PATCH v2 26/30] fuse: Add logic to free up a memory range

Sunday, 19 May 2019


Hi,

@@ -1784,8 +1822,23 @@ static int fuse_iomap_begin(struct inode *inode,
...
 loff_t pos, loff_t length,
                 if (pos >= i_size_read(inode))
                         goto iomap_hole;

 -               alloc_dmap = alloc_dax_mapping(fc);
 -               if (!alloc_dmap)
 +               /* Can't do reclaim in fault path yet due to lock ordering.
 +                * Read path takes shared inode lock and that's not
 sufficient
 +                * for inline range reclaim. Caller needs to drop lock,
 wait
 +                * and retry.
 +                */
 +               if (flags & IOMAP_FAULT || !(flags & IOMAP_WRITE)) {
 +                       alloc_dmap = alloc_dax_mapping(fc);
 +                       if (!alloc_dmap)
 +                               return -ENOSPC;
 +               } else {
 +                       alloc_dmap = alloc_dax_mapping_reclaim(fc, inode);
 
alloc_dmap could be NULL as follows:

alloc_dax_mapping_reclaim
   -->fuse_dax_reclaim_first_mapping
             -->fuse_dax_reclaim_first_mapping_locked
                  --> fuse_dax_interval_tree_iter_first  ==> return NULL
and

IS_ERR(NULL) is false, so we may miss that error case.

...
 +                       if (IS_ERR(alloc_dmap))
 +                               return PTR_ERR(alloc_dmap);
 +               } 

Regards,
Eric

    